Prohexadione Calcium Does Not Affect Thinning Efficacy of 1-aminocyclopropane-1-carboxylic Acid in ‘Golden Delicious’ - Annie Vogel Carbohydrate Status of Apple Fruitlets following Chemical Thinner Application Informs Sink Strength and Fruit Set - Laura Hillmann Performance of a reflectance spectroscopy model to predict apple fruitlet thinning efficacy - James Larson Overexpression of the Coding Sequence of Ma1 Decreases Fruit Acidity in ‘Royal Gala’ Apple - Lailiang Cheng Striking the Right Balance: Innovative PGR Strategies for Fruit Drop Mitigation and Color Enhancement in Apples - Sherif Sherif Rapid Fruit Growth Rates of Honeycrisp Apples Cause Premature Dysfunction of Xylem, Reduced Peel Calcium, and Increased Susceptibility to Bitter Pit - Chayce Griffith Carbohydrate And Nitrogen Storage Are Inversely Affected By Crop Load For 'Honeycrisp' And 'Gala' Apples - Thiago Campbell Impacts of Rootstock and Crop Load Adjustment on Fruit Quality and Mineral Nutrients in ‘Honeycrisp’ Apple - Esmaeil Fallahi
Apple’s (Malus × domestica Borkh.) tendency towards biennial bearing necessitates management strategies such as fruit thinning and vigor control. Applications of plant growth regulators to manage crop load and vigor overlap in the spring. A precursor to ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC; Accede®) was recently registered as a chemical fruit thinner in the USA. Prohexadione-calcium (P-Ca) is a gibberellin biosynthesis inhibitor widely used to manage vigor. It is suspected that P-Ca may interfere with ACC precursors, decreasing thinning efficacy of ACC. We evaluated the effects and interactions of ACC and P-Ca on shoot growth, ethylene evolution, leaf area, and yield responses of mature ‘Golden Delicious’. The experiment was conducted in 2023, in Mills River, NC, USA. Treatments included ACC (400 mg∙L-1), P-Ca (250 mg∙L-1), ACC P-Ca, and an untreated control. Application of P-Ca occurred on three dates. ACC was applied when average fruit diameter was ~20 mm. Across all measured responses, there were no interactions between ACC and P-Ca. P-Ca had a negative main effect on shoot growth rate (48.7–75.4% reduction). ACC reduced leaf number of spurs 4 and 9 days after treatment (DAT). Ethylene evolution in fruit and spurs was increased by ACC 1, 4, and 9 DAT (spur: 1.1e4%, 5300%, and 515%, respectively; fruit: 9200%, 725%, and 222%, respectively). ACC had a negative effect on fruit number, yield, and crop density (60.1%, 56.5%, and 60.3% reduction, respectively). These results indicate that ACC and P-Ca can be used simultaneously to manage crop load and vigor, respectively
Crop load management of apple (Malus x domestica Borkh.) is one of the most important orchard management practices to ensure adequate fruit size and quality. Fruitlets are most sensitive to thinner applications early in the season, between 6mm and 20mm fruitlet diameter. During this time, abscission is associated with environmental and biological factors that influence fruitlet development, growth and sink strength. The carbohydrate economy of the fruitlet and its position within the cluster (king flower vs. lateral flowers) are primary factors contributing to the sink strength of individual fruitlets. We evaluated the relationship between the non-structural carbohydrate status of apple fruitlets in three different size classes (i.e., 90th, 50th, and 10th percentile of the population) and their respective likelihood to persist throughout the season. Persistence probabilities of these size classes were generated by an empirical fruit set prediction model based on the distribution of fruitlet mass and confirmed by actual measures of fruit set. Soluble carbohydrates and starch were quantified with an enzymatic assay procedure. Following chemical thinner application, the concentration of soluble sugars (glucose, fructose, sucrose, and sorbitol) was significantly reduced on a gram / gram fresh weight basis. Fruitlets in the 10th percentile generally had the lowest concentration of soluble sugars and starch and the slowest recovery rate following chemical thinner application. Fruitlets in the 90th percentile generally had the highest concentrations of soluble sugars and starch. Our data support that differences in the carbohydrate concentration of fruitlets contribute to their sink strength and abscission fate as predicted by a fruit set prediction model.
Post-bloom apple chemical thinning relies on the application of plant bioregulators to induce fruitlet abscission, reducing crop load to improve fruit quality and promote return bloom. Abscission rates following chemical thinner application are influenced by carbohydrate status of the tree and thus widely variable. Multiple applications are often needed for growers to reach a desired crop load. However, trees are only perceptive to chemical thinners for a 3 to 4 week period shortly after bloom. Rapid prediction of chemical thinner efficacy is critical to allow growers to make necessary applications in this narrow period of time without the risk of over-thinning. In 2021 and 2022 a predictive model using reflectance spectroscopy measured with a handheld spectrometer (Felix F-750; Felix Instruments; Camas, WA, USA) was developed to predict chemical thinner efficacy for ‘Honeycrisp’ in North Carolina, USA. This model was found to predict chemical thinner efficacy with greater than 85% accuracy as early 3 days following a chemical thinner application. In 2023 and 2024 validation of this model occurred on multiple cultivars: ‘Red Delicious’, ‘Granny Smith’, ‘Gala’, and ‘Fuji’; and in multiple growing regions: Michigan, New York, and North Carolina, USA. Performance of the developed model to predict chemical thinning efficacy in this wide range of situations will be discussed to determine commercial applicability of the model.
Vacuolar accumulation of malic acid, the predominant organic acid in apple (Malus domestica) and many other fleshy fruits, largely determines fruit acidity, a key trait for fruit taste and flavor. ALUMINUM-ACTIVATED MALATE TRANSPORTER 9 (ALMT9/Ma1) underlies a major genetic locus, Ma, for fruit acidity in apple. A natural mutation at base 1455 leads to a pre-mature stop codon that truncates the Ma1 protein by 84 amino acids to ma1, and this truncation significantly reduces Ma1’s malate transport activity by disrupting a conserved C-terminal domain, leading to low fruit acidity in recessive homozygous ma1ma1 genotypes. However, it remains unclear how Ma1 functions to transport malate across the tonoplast membrane. When the coding sequence of Ma1 was overexpressed in ‘Royal Gala’ apple (Ma1ma1) to determine its in planta function, to our surprise, the transgenic fruit had drastically reduced fruit acidity compared with the wild-type (WT). This led us to uncover that Ma1 undergoes alternative splicing. Two isoform proteins are generated by alternative splicing: Ma1beta being 68 amino acids shorter with much lower expression than the full-length protein Ma1alpha. Ma1beta does not transport malate itself, but interacts with the functional Ma1alpha, creating synergy with Ma1alpha for malate transport in a threshold manner when Ma1beta is equal to or exceeds 1/8 of Ma1alpha. In WT ‘Royal Gala’, Ma1 operates at this threshold. Overexpression of Ma1alpha triggers feedback inhibition on the native Ma1 expression via transcription factor MYB73, decreasing the Ma1beta level well below the threshold that leads to significant reductions in Ma1 function and malic acid accumulation in fruit. Overexpression of Ma1alpha and Ma1beta or genomic Ma1 increases both isoforms proportionally and enhances fruit malic acid accumulation. These findings reveal an essential role of alternative splicing in Ma1-mediated malate transport underpinning apple fruit acidity.
Biennial or alternate bearing is characterized by an abundance of blooming and fruiting in “on” years and a lack of blooming and fruiting in “off” years. Biennial bearing in fruit tree production has been extensively studied. However, it continues to be problematic in certain crops and cultivars. Fundamental physiological mechanisms controlling this behavior are still poorly understood. Along with carbohydrates in plant tissues, reserve nitrogen influences early-season growth in apples, with the percent contribution of reserve nitrogen being dependent on the current nitrogen supply. Because flowering and fruit set occur in spring alongside bud break, reserve nitrogen can significantly affect these processes too. We sought to understand the role carbohydrate and nitrogen storage in various plant tissues has on biennial bearing for ‘Honeycrisp’ apple. Apical buds, terminal shoots, and one-year-old spurs were collected in 2022
In apple orchards, addressing pre-harvest fruit drop in early-maturing, commercially valuable cultivars like ‘Honeycrisp’ and ‘Gala’ is crucial. This issue is largely linked to ethylene, a ripening hormone that, despite its role in enhancing fruit qualities, triggers premature fruit drop. From 2018 to 2021, extensive field trials were conducted across commercial and experimental orchards to refine the application of two ethylene-inhibiting products, ReTain (AVG-15%) and Harvista (1-MCP-1.3%), in mitigating this challenge in ‘Gala’ apples. Our findings confirmed AVG’s effectiveness in reducing fruit drop and stem-end splitting; however, AVG application consistently resulted in diminished fruit coloration. In the subsequent seasons of 2023 and 2024, our research pivoted towards identifying plant growth regulator (PGR) formulations that could balance the dual objectives of minimizing fruit drop and preserving color development in ‘Honeycrisp’ and ‘Gala’ apples. Key findings include: a) the multiple applications of Accede (ACC-10%) and Motivate (Ethephon-21.7%) starting from three weeks before harvest significantly enhanced red color formation in ‘Honeycrisp’ and ‘Gala’ apples, surpassing control and ReTain treatments, though Motivate increased the rate of fruit drop; b) ReTain, both alone and in combination with Accede, notably reduced fruit drop, with the ReTain-Accede mix also enhancing fruit coloration; c) combining ReTain and Motivate neither decreased fruit drop nor enhanced color; d) the positive impact of the ReTain-Accede mix on color was biochemically and molecularly validated; e) Accede's color-enhancing effect appears to be ethylene-independent. This research underscores the potential of specific PGR mixes in achieving a harmonious balance between reducing fruit drop and enhancing fruit coloration.
Dr. Sherif M. Sherif is an Associate Professor at Virginia Tech, where he channels his fervent zeal for life sciences and educational outreach into his specialization in tree fruit physiology and molecular biology. His career is defined by a dedication to overcoming the biological... Read More →
The influence of rootstock and time of crop load adjustment on ‘Honeycrisp’ apple fruit quality at harvest and after storage was studied over four seasons. Yield per trees varied from year to year because of biennial bearing. Trees on V.1 and G.30 were higher while those on G.969 often had lower yield per tree. Fruit from trees on M.26EMLA and G.30 were larger, while those on G.202 and G.969 were smaller than those on other rootstocks in two of three years. Fruit firmness at harvest and after storge was often inversely proportional to their size, so that fruits from trees on G. 202 often had higher but those on G.30 often had lower firmness at harvest and after storage. Percentages of fruit bitter pit among rootstocks at harvest was different than those after storage. However, fruit from trees on M.26EMLA, V.1, and G.30 generally had higher bitter pit than those on G.969 and G.202 rootstocks. Fruit fresh weight continually grew during growing season. However, the increase in percentage fruit dry weight reached a plateau on August 9, after which it leveled off. Trees receiving an “Early Heavy Thinning” and “Thinned Early to 1 Fruit/bunch” had lower yield but larger fruit with more bitter pit than Un-thinned-Control trees. Trees receiving a thinning on June 11 and June 25 had similar fruit size in the same season. However, bitter pit was increased, while fruit size decreased, as the hand thinning was delayed until July 8. Late hand thinning resulted in smaller fruit size with less bitter pit. Fruit potassium/ calcium (K/Ca) ratio did not change significantly between June 20 and August 8 within the same year. This research unveils importance of rootstock, time, and level of and thinning in the fruit quality of ‘Honeycrisp’ apple.
Insufficient transport of calcium to and throughout the cortex of apple is a primary factor contributing to bitter pit, a disorder characterized by dark lesions on the fruit surface. Calcium transport, in-planta, occurs solely in the xylem. Progressive transport dysfunction of xylem limits calcium concentration in the peel and subtending tissue. Rapid fruit growth may accelerate xylem dysfunction due to the stretching, shearing, or compressing of xylem elements. The relative time course of these events and subsequent effect on calcium concentration of peel tissues is not well understood. Growth rate of fruit was manipulated by manually adjusting the crop load of 6th leaf ‘Honeycrisp' trees to either 4 (low), 8 (moderate), or 16 (high) fruit per cm2 of trunk cross-sectional area via bud extinction. Fruit mass, xylem functionality, and peel calcium content were assessed weekly throughout the season. Fruit tissues were frozen weekly to evaluate the expression of genes related to xylogenesis and calcium transport and for quantification of hormones. At maturity, 25 trees were harvested from each crop load treatment. Fruit were assessed for bitter pit, stored for three months in regular air (3⁰C), then reassessed. Crop load influenced both xylem functionality and bitter pit incidence of fruit. Low crop load fruit lost 80% of xylem functionality by 8 weeks after bloom, which was two weeks earlier than moderate crop. By seven and five weeks before harvest, total xylem dysfunction was observed in fruit of low and moderate crop load, respectively; xylem in high crop load fruit never became fully dysfunctional. Final fruit mass from low crop load trees was only 20 grams larger than fruit from moderate crop load trees, yet, these fruit had a roughly 100% increase in bitter pit incidence at harvest (27.3% vs. 12.6%). Only 4.1% of high crop load fruit were affected by bitter pit. Many previous studies have ascribed the positive relationship between fruit mass and bitter pit incidence to calcium dilution. Our data suggest, however, that the issue is one of transport limits that appear to begin very early in fruit development, exacerbated by the growth rate of fruit, resulting in less peel calcium and higher bitter pit incidence at harvest than fruit of relatively lower growth rates. Future analysis of endogenous hormone concentrations and expression of genes relating to xylogenesis and calcium allocation will facilitate a better understanding of the processes governing xylem dysfunction and its association to bitter pit disorder.
Dr. Randolph Beaudry, Professor, MSU Department of Horticulture (MSc, PhD, University of Georgia). His appointment is 50% MSU Extension and 50% AgBioResearch. His research program includes both regional and international projects and focuses on the physiology of plant responses to... Read More →
Consumer Preference and Willingness-to-Pay for Pawpaw Value-Added Products - Sheri Crabtree Promising Advanced Selections from Kentucky State University’s Pawpaw (Asimina triloba) Breeding Program. - Jeremy Lowe Assessment of Fruit Quality and Value-added Potential of 16 Pawpaw Cultivars and Advanced Selections - Kirk Pomper Effects of Temperature and Light on Sunburn, and Preventing the Sunburn Damage by Chemical Suppressants in ‘Fuyu’ Sweet Persimmons - Yunji Shin Crown Gall Associated with Higher Risk of New Butt Rot Pathogen in California Almond Orchards - Raymond Mireles
The North American pawpaw (Asimina triloba) is the largest edible tree fruit native to North America, with a flavor resembling a unique tropical-like blend of mango and banana. Commercial production and consumer interest in pawpaw is on the rise in the US and worldwide. Fresh pawpaw fruit has a short shelf life and does not store or ship well. Value-added products represent a great potential market to both diversify offerings of products containing pawpaw, and provide shelf-stable products that could be available year-round and circumvent the storage and shipping challenges of fresh fruit. Pawpaws can be utilized in many value-added products, including ice cream, yogurt, jam, custard, baked goods, hot sauces, wine, beer, and brandy. A pawpaw value-added product tasting was conducted in September 2023 at the Kentucky State University Research and Demonstration Farm as part of the annual Pawpaw Third Thursday Thing workshop. Participants tasted samples of slices of fresh pawpaw fruit of six varieties, pawpaw jam on crackers, and pawpaw ice cream. A survey was conducted evaluating preference and interest in purchasing pawpaw fruit, jam, and ice cream, and willingness to pay. The survey found that 93% of participants would be interested in purchasing pawpaw fruit at a farmers market, compared to 80% at a grocery store and 88% at an on-farm market or roadside stand. Ninety-five percent (95%) of participants would be interested in purchasing pawpaw jam if available in stores, and 95% of participants would also be interested in purchasing pawpaw ice cream if available in stores. Respondents would be willing to pay $2.20 per fruit, or $4.97 per pound for fresh pawpaw fruit. Respondents reported they would pay $7.22 for an 8 ounce jar of pawpaw jam, and $8.51 for a quart of pawpaw ice cream. Currently, pawpaw ice cream and jam are sold by very few retailers in specialty markets, so there is great opportunity for pawpaw producers to introduce high-value pawpaw products that are desired by consumers to their retail markets.
Dr. Kirk W. Pomper is the Professor of Horticulture in the College of Agriculture, Community, and the Sciences at Kentucky State University in Frankfort, Kentucky. As Horticulture Research Leader, his program is focused on research and Extension efforts toward developing pawpaw as... Read More →
The North American Pawpaw (Asimina triloba) is a tree fruit native to the Eastern U.S. which is being produced in commercial orchards across the U.S. and internationally, with an increasing market and interest. There are approximately 50 pawpaw cultivars available, but many of these varieties have low yields with fruit sizes below the threshold of 120 grams needed for commercial sale and processing. New high yielding cultivars with excellent fruit quality would further assist in the development of the pawpaw industry. Kentucky State University serves as the National Clonal Germplasm Repository for Pawpaw. Two goals of the Repository research efforts are germplasm acquisition and evaluation. The repository contains over 2000 accessions from 16 different states; additionally, both open pollinated seedlings from superior genotypes and crosses of superior selections have been incorporated into the repository collection. Fruit weights from three of KSU’s advanced selections (Hi 1-4, Hi 7-1, and G6-120) were compared to the cultivars ‘KSU-Atwood’, ‘KSU-Benson’, ‘KSU-Chappell’, ‘Ralph’s Whopper’, and ‘Sunflower’. Fruit weights for Hi 1-4 (241.5 g) and Hi 7-1 (233.5 g) were significantly larger than ‘Sunflower’ (145.3 g). Hi 1-4 and Hi 7-1 show potential to be promising new releases and have been budded onto seedling rootstock for further evaluation.
Dr. Kirk W. Pomper is the Professor of Horticulture in the College of Agriculture, Community, and the Sciences at Kentucky State University in Frankfort, Kentucky. As Horticulture Research Leader, his program is focused on research and Extension efforts toward developing pawpaw as... Read More →
The North American pawpaw [Asimina triloba (L.) Dunal] is a native tree-fruit that is in the early stages of commercial production in the United States. Pawpaw fruit have fresh market appeal for farmers markets, community supported agriculture, and organic markets, as well as processing potential for frozen pulp production. For the processing market, fruit with a large size of over 120 grams and less than 6 percent seed by weight, are desirable for processing for pulp recovery for value-added products such as hot sauce. Kentucky State University has already released three pawpaw cultivars, KSU-AtwoodTM in 2009, KSU-BensonTM in 2016, and KSU-ChappellTM in 2018. However, new high yielding cultivars with excellent fruit quality would further assist in the development of the pawpaw industry. The objective of this study was to determine the fruit quality of 16 pawpaw cultivars and advanced selections. Fruit weight, percent seed, and brix were determined for the cultivars and advanced selections grown at the Kentucky State University Research and Demonstration Farm in Frankfort, Kentucky. The cultivars and advanced selections evaluated were A3-1, A6-1, KSU-AtwoodTM, KSU-BensonTM, KSU-ChappellTM, G4-25, G6-120, G9-109, Hi 1-4, Hi 7-1, Hy3-120, NRVT 3-10, NRVT 3-4, Sunflower, Susquehanna, and Tallahatchie. Average fruit weight ranged from Tallahatchie at 138g to A-6-1 at 277g per fruit. A number of advanced selections had large fruit size and these included A6-1 (277g), Hy3-120 (258g), A3-1 (216g), Hi1-4 (214g), NRVT3-4 (208g), Hi7-1 (202g) and G9-109 (201g). Average percent seed for fruit ranged from G6-120 at 8.2 percent seed to the cultivar KSU-ChappellTM at 4.5 percent seed. A number of advanced selections had low percent seed and these included A6-1 (4.7%) and G4-25 (5.8%). Average percent Brix for fruit ranged from NRVT 3-10 at 19.8 Brix to the cultivar KSU-ChappellTM at 28.2 Brix. Many of these advanced selections show promise as potential new cultivars. Examples of hot sauce made from pawpaw pulp extracted from cultivars will be discussed.
As global warming progresses, sunburn damage in fruit production is becoming increasingly prevalent. However, there has not been much research on the patterns of sunburn occurrence and effective prevention measures for ‘Fuyu’ sweet persimmons. This pilot study explored the impact of strong light and high temperatures on sunburn occurrence in ‘Fuyu’ sweet persimmons, characterized the temporal pattern of sunburn development, and evaluated the efficacy of chemical suppressants in reducing damage. ‘Fuyu’ persimmons were harvested from an orchard in Jinju-si, Gyeongsangnam-do, South Korea, at 60 days (weak light intensity (WLI) conditions), 72 days (strong light intensity I (SLI-I) conditions), and 79 days (strong light intensity II (SLI-II) conditions) after full bloom. The harvested fruits were divided into five treatment groups: control (Distilled water), 2% Cellulose Nano Crystals (CNCs), 2% Sodium Alginate 300mM CaCl2 (AG), 6% Kaolin 0.1% Tween20 (K), and 2% Vapor Gard® (VG, transpiration inhibitor). Thermocouples were attached to each fruit to measure fruit surface temperature (FST) under the following conditions: WLI (using a chamber set to 200 µmol/m²/s light intensity) and SLI-I, -II (direct sunlight and temperature) conditions. When exposed to WLI conditions, the increase in fruit surface temperatures (FST) compared to air temperatures (AT) was minimal, and no sunburn was observed. Conversely, non-acclimated fruits exposed to SLI-I displayed extensive sunburn damage within a day. However, acclimated fruits under SLI-II revealed differences in sunburn. The kaolin treatment, which exhibited the lowest browning, also showed a significant reduction in FST. However, the carotenoid content was lower in the kaolin treatment compared to the control. To confirm the findings from controlled experiments, field trials were conducted for two years to evaluate the effectiveness of sunburn suppressants. In the first year, kaolin treatment reduced the severity of sunburn by half compared to other chemical suppressants. In the second year, 6% kaolin and a mixture of kaolin and carnauba wax were applied. Both kaolin and a kaolin-carnauba wax mixture effectively reduced sunburn to 30% of the control. These effective treatments decreased FST by up to 3.5℃, maintained high chlorophyll content, and augmented antioxidant enzyme activities. In conclusion, the kaolin treatment combined with carnauba wax was identified as the most promising material for preventing sunburn damage in ‘Fuyu’ persimmons under these environmental circumstances.
The wood decay fungus, Ganoderma adspersum, with no prior record in North America has emerged as a pathogen of almond in the San Joaquin Valley within the past decade. Incidence of the disease appears highest in orchards on ‘Nemaguard’ rootstock with high levels of crown gall, a bacterial disease caused by Agrobacterium tumefaciens. The putative association of G. adspersum with crown gall has been hypothesized, but not formally evaluated in the field. In February 2024, over 6,000 trees were surveyed across two orchards and rated for incidence of each disease. Both orchards were on ‘Nemaguard’ rootstock and included ‘Nonpareil,’ ‘Monterey,’ and ‘Fritz’ varieties. Results of Chi-square test for binomial ratings of two categorical variables indicate a significant association between G. adspersum and crown gall infection on all varieties in both orchards. Furthermore, when the variables were fitted using the generalized linear mixed model, infection with G. adspersum (independent variable) was found to have a significant effect on the association (response variable) for ‘Nonpareil’ variety at one site. For each unit increase in the incidence of crown gall, the probability of infection with G. adspersum increased by more than 1×109 fold on ‘Fritz’ and ‘Monterey’ at both sites, and ‘Nonpareil’ at one site, and by more than 87-fold on ‘Nonpareil’ at the second site. The results support the hypothesis that crown gall predisposes almonds to infection by G. adspersum. Further studies are needed to address the mechanism by which crown gall infection predisposes almond to G. adspersum with the long-term goal of improving the economic lifespan of California almond orchards.
Mechanization Reduces Pruning and Harvest Labor Time in the Cider Apple Orchard - Carol Miles Testing Agronomic Strategies to Reduce Biennial Bearing in Apples - Thiago Campbell Identifying Local Apple Germplasm for Use of Hard Ciders in North Dakota - Wenhao Dai The Fruitlet Size Distribution Model As A Thinning Decision Aid For Precision Crop Load Management Of Apple - Laura Hillmann Deciphering the Proline-Mediated Flowering Delay Mechanism in Peach through Physiological and Metabolic Analyses - Hyunsuk Shin Genetic Architecture of Important Traits for Prunus Crop Improvement - Michael Itam Taste Acidity and Other Important Fruit Characteristics of New Peach Varieties Compared with Concurrent Varieties During 2022 and 2023 - Hemant Gohil Role of Silicon in Peach Water Stress Tolerance - Noah Willsea
Biennial bearing in tree fruit can be problematic, and these patterns are not unique to tree fruit and occur in natural species. Masting, or the abundant production of seeds in some years, can also be observed in natural tree species. Despite extensive research, biennial bearing still affects commercial orchard production. Biennial bearing cycles are costly, with inconsistent yields and fruit quality occurring yearly. Crop load management is one commonly used management strategy to control biennial beating. However, trees can continue a biennial cycle the year following adequate crop thinning. We evaluated six different agronomic strategies to combat biennial bearing in apple trees; two for low-cropping trees (“off” year) and four for high-cropping trees (“on” year). In 2023, ‘Honeycrisp’ trees on B.9, G.41, G.890, and M.9-T337 rootstocks in their high-cropping year were root pruned, girdled, sprayed with ethephon, or fertilized with nitrogen (ammonium nitrate) in the fall, along with untreated control. Trees in their low-cropping year (2023) were defoliated and sprayed with gibberellic acid (GA 3 ) and untreated control. Due to the limited availability of low-cropping trees in 2023, only ‘Honeycrisp’ trees on B.9 and M.9-T337 rootstocks were used. All treatments were applied two to three weeks after full bloom except for nitrogen fertilization, which was applied in late August. Crop load, vegetative growth, and fruit quality were measured for treated trees and controls. Carryover effects of treatments were calculated to quantify the reduction/amelioration of biennial bearing incidence. In low-cropped trees, GA 3 had significantly higher return bloom from controls and defoliated trees. In high-cropped trees, no treatment had a significant effect on return bloom compared to controls. Vegetative growth was not affected by any treatment. Effective agronomic strategies for managing biennial bearing can be inconsistent and need to be further investigated for their impacts.
Hard cider is one of the fastest growing specialty beverages in the United States with an average annual retail sales of about $500 million in recent years. Cider apples refer to those that are specifically used for hard ciders (alcoholic) with unique traits, such as high acid, high tannin, and high total soluble solid that help ferment superior-quality hard ciders. In traditional hard cider production countries, hard ciders are made from cider-specific cultivars; however, hard ciders in the US are usually made from apples that were bred for fresh apple market because of inadequate fruit availability of cider-specific cultivars. In this study, apple germplasm grown at the NDSU Horticulture Research Farm near Amenia, ND (USDA hardiness zone 3-4a) was evaluated for the suitability of quality hard ciders. Specifically, four biochemical traits, total soluble solids (TSS), pH, titratable acidity (TA), and total phenolic compounds (TPC) that are the general attributes to the quality of hard ciders, were analyzed. Preliminary results showed that the average TSS was 15.75o Brix with the highest TSS reached 21.2o Brix. The fruit of some lines were very sour and tart indicating the high level of acidity and phenolics, which showed the great potential for quality hard cider production. The titratable acidity (malic acid) and total phenolic compounds in the apple juice of selected lines are being quantified. This research could identify local cider apple germplasm and provide apple growers and cider makers with the information on cultivar selections for quality hard cider production in ND and the surrounding region.
Fruit quality of apple is heavily influenced by crop load management practices. During the developmental window between bloom and 15mm fruitlet diameter, the general commercial practice is to apply chemical thinners to reduce the initial crop load based on the cultivar and market. However, thinning success varies from year to year, depending on bloom density, thinner selection and dose, climatic factors, tree health and cultivar. Precision crop load models such as the pollen tube growth model, the MaluSim model, and the fruit growth rate model have improved thinning success; however, labor-intensive measures has hindered broad adoption of the latter model which effectively predicts fruit set following thinner application. To improve grower adoption, we developed an alternative, time-efficient fruit set prediction model. The model has been tested on multiple cultivars over a three-year period at four distinct apple production regions throughout the United States. Abscission probabilities and fruit set predictions are based on the distribution of fruitlet mass and confirmed by actual measures of fruit set. The model starts at 6 mm fruitlet diameter and accounts for all thinners up to this time. A prediction is returned in ~8 days to inform repeat thinner applications while fruitlets are still highly sensitive to thinners. A user-guide, digital balance that automatically exports fruit mass to a laptop/tablet, and a macro-enabled Excel spreadsheet file have been developed and are available to growers to increase the precision around crop load management.
Freezing temperatures can harm peaches in late spring with advanced flowering due to climate change and consequently reduce their yield. Flowering delay is a prominent strategy employed to avoid such spring frost damage. Our previous study demonstrated that treatment with 5% sodium alginate 100 mM CaCl 2 (5AG) can delay the blooming, potentially avoiding frost damage. To elucidate the precise mechanism of flowering delay induced by 5AG in peaches, this study systematically and experimentally analyzed the changes of amino acid profiles in control and 5AG-treated peach plants at different day intervals (0, 1, 2, 11, 21, 25, and 28 DAT). Our findings revealed that the levels of arginine (Arg), glutamate (Glu), and proline (Pro) differed significantly between control and 5AG- treated peach shoots throughout the phenological development of flower buds. Furthermore, Arg and Glu amino acids, are involved in the Pro pathway. Computational metabolomics analyses identified the Pro metabolism related genes and their attributes, gene ontology, gene synteny and gene organizations, which represent diverse biological function of these genes, including flowering responses. In addition, qRT-PCR analysis results revealed that elevated expression of P5CS and P5CR genes, involved in Pro metabolism, led to increased Pro content in control plants. Conversely, 5AG treatment downregulated these genes, resulting in lower proline content. This result suggests that 5AG treatment may restrain gene expression related to Pro accumulation, thereby controlling Pro biosynthesis. In addition, our findings unveiled a direct connection between Pro content reduction and delayed flowering. Taken together, these results provide strong evidence that 5AG treatment significantly delays flowering by controlling Pro metabolisms in Prunus persica.
Numerous QTL and GWAS studies have been conducted on various species of Prunus, but there is limited knowledge on the overall genetic architecture regulating fruit quality traits among these species. As part of a 2022-funded SCRI- project to advance database resources for specialty crop research, efforts are directed towards collecting and curating all types of big data in the Genome Database for Rosaceae (www.rosaceae.org). We conducted an extensive literature review on over 120 QTL and GWAS studies on Prunus traits to extend the existing data in GDR. We aligned the traits to the peach genome to compare important traits in various Prunus species. The consensus map showing QTL hotspots will be accessible using various tools in GDR. Implications of the newly created resources and tools in GDR for breeding will be discussed.
Three new peach varieties and ‘Felicia’ ‘Evelynn’ and ‘Anna Rose’ were recently released from the Rutgers University tree fruit breeding program. These varieties are concurrent with some of the standard peach varieties. The comparison of taste acidity and other important fruit characteristics could help growers choose in case of planting these varieties or replacing the standard varieties during the same harvest window. Fruit characteristics such as flesh color, crop load, shape, skin color, fuzz, attractiveness, stone characteristics (free, semi-free, or cling), flesh color, bacterial spot, on fruits and leaves, taste acidity, juice total soluble solids (TSS) concentration (°Brix), and total titratable acidity (TTA) (%) were measured. Here we compare these varieties to highlight the differences and challenges amongst these varieties on their path to full consumer appreciation. Results indicate that average TSS and firmness were higher in ‘Felicia’ (12.9 brix; 12.4 lb) and ‘Evelynn’ (11.9 brix; 10.9 lbs.) compared to ‘Redhaven’ (11.1 brix; 8.14 lbs.). Also; average TSS and firmness were higher in ‘Anna Rose’ (14.4 brix; 13.68 lbs.) compared to ‘Klondike’ (12.0 brix; 11.3 lbs.) and ‘White Lady’ (10.9 brix; 9.64 lbs.). In summary, new yellow-fleshed peach varieties ‘Felicia’ and ‘Evelynn’ have great potential to replace the old standard variety, ‘Redhaven’. Similarly, the new white-fleshed peach variety ‘Anna Rose’ has great potential to replace old standard varieties ‘White Lady’ and ‘Klondike’.
Water stress in young fruit trees can reduce tree growth and impair future crop productivity. Silicon (Si) has shown a positive effect in mechanisms related to water relations, specifically water uptake and transport, as well as physiological and anatomical changes in leaves of annual plants. These findings suggest that Si could induce adaptive changes that could help trees cope with water deficit. The objective of this experiment was to evaluate the role of Si on water status, sap flow, and gas exchange of young peach trees under water deficit. Two-year-old ‘Julyprince’ peach trees grown under controlled conditions received either 100% (well-watered trees) or 50% (stressed trees) of their crop evapotranspiration needs three times a week. Once trees in the two treatments displayed a difference in water status, Si was applied weekly by foliar spray (0 or 20 mg L-1). The combination of these two factors resulted into a completely randomized factorial design with four treatments. Results showed an interaction between irrigation regime and Si application. Si increased sap flow in well-watered trees and reduced that of stressed trees, although this effect was more significant the day after irrigation. Furthermore, Si significantly improved the water status of trees under water deficit but did not influence that of well-watered trees. These results seem to indicate that the role of Si in improving tolerance to water deficit is temporary and dependent on the tree water status.
While fresh-eating, dessert apples dominate the apple market of Washington State, the over 30-fold national increase in volumetric cider production over the past 15 years indicates there is growing demand for specialty cider apples, or apple cultivars with positive cider-making attributes such as high polyphenol content. In a commercial cider orchard, the labor costs associated with thinning, pruning, and harvest comprise a majority of the annual variable production costs once the orchard is in full production; thus, reducing the labor time to perform these tasks has the potential to increase the appeal and profitability of growing cider apples. Further, when cider apples are pressed into juice soon after harvest, cosmetic damage and bruising of the fruit during harvest has minimal impact on juice quality, indicating a strong potential for harvest mechanization. This study separately examines mechanical hedging and mechanized over-the-row harvest (using a modified Oxbo-Korvan 930 harvester) in a multi-cultivar cider apple orchard. Mechanical hedging both sides of the orchard row occurred at a rate of 2.1-3.5 seconds per meter across 5 years. Across 16 cultivars and 3 years, mechanical harvest occurred at a rate of 2.7-3.1 seconds per meter, and the average capture efficiency was 82% with no significant differences between cultivars. Based on these results, a combination of mechanical pruning and harvest could significantly lower labor time, and thus the total production costs, associated with growing cider apples.
A forum for discussion of potential collaborations with regards to fruit, vegetable, and edible crops – i.e. citrus, breeding, production systems, postharvest, pomology, crop management, viticulture, etc.
Wednesday September 25, 2024 2:00pm - 3:00pm HST
Coral 4
Do Plant “Growth Regulators” Really Regulate Growth? Plant Development And Plant Growth Are Not Synonymous. - Ted DeJong Using GDR to Enable Rosaceae Research - New Data, Functionality and Future Direction - Dorrie Main Deployment of Multi-location Genomic Prediction Models for Fruit Crops Using GDR-BIMS - Craig Hardner Raspberry Cultivar Evaluation Trial in Mississippi - Apphia Santy Performance of AU Gold-fleshed Kiwifruit in Alabama - James Spiers Evaluating Sufficiency Levels and Peach Leaf Analysis for Fertilizer Decision-Making - Juan Carlos Melgar
Much scientific literature refers to plant development and growth as though they are synonymous. While plant physiology texts (E.g., Taiz et al. 2015) and horticulture texts (E.g., Sansavini et al. 2019) emphasize the roles of various plant hormones in coordinating plant development, they simultaneously refer to them as plant growth regulators. On the other hand, the same texts emphasize assimilation processes and the important role of carbohydrate and nutrient availability as well as water relations in enabling growth to occur. The terms growth and development are often used interchangeably and the literature rarely emphasizes the difference between plant development and plant growth. This causes confusion and a lack of clear thinking when attempting to develop explanations for plant growth responses in specific circumstances. Hormone physiologists often try to explain particular growth responses in terms of hormonal theory whereas environmental physiologists will likely explain the same responses in terms of environmental conditions and availability for the resources required for achieving growth. In this paper I will argue for a clearer differentiation between plant development and plant growth and suggest that plant hormones should not be thought of as plant growth regulators, but rather as plant development coordinators. Plant development coordinators (plant hormones) set up the conditions necessary for plant growth but availability of plant growth substances; carbohydrate and nutrient availability along with temperature and water relations, are often what actually regulate plant growth rates. Treating development and growth as separate but interdependent processes could clarify much understanding of the underlying processes involved in the regulation of plant growth. These concepts will be discussed in the context of understanding the mechanisms involved in several physiological phenomenon of fruit trees.
Initiated in 2003, the Genome Database for Rosaceae (GDR, www.rosaceae.org) is a comprehensive community database that provides access to curated and integrated genomics, genetics, and breeding data for the biologically and economically important Rosaceae family. It serves as steward of critical research and breeding data, and provides access to online query and analysis tools that enable researchers to readily interrogate this wealth of data, facilitating basic and applied research across Rosaceae. This presentation will highlight the impact of GDR on Rosaceae research, demonstrate new data and tools, and share plans for future development and sustainability options.
I am a member of the Pullman Charter School Initiative team and am particularly interested in how to set up and maintain a thriving Washington State Charter School to serve the needs of Eastern Washington students.
Wednesday September 25, 2024 2:45pm - 3:00pm HST
Nautilus 1
Multi-location genomic prediction models have been proposed as a strategy for aggregating disconnected phenotypic datasets to enable performance prediction of individuals into new environments. This approach also offers improved prediction accuracy and understanding of environmental stability. Multi-location GBLUP prediction models have been developed and used to study patterns in genotype-by-environment interaction for: flowering date in cherry across four locations in USA, France, and Italy; for sweetness in peach across four locations in USA; in strawberry across eight locations in USA, Australia, and Europe; and for fruit firmness in apple across five locations in USA and Europe. Here we present an online bioinformatics platform for the deployment of these models via the Breeding Information Management System (BIMS) in the Genome Database for Rosaceae (GDR). This platform enables performance of new material that has not been physically tested to be predicted for the traits across the environmental space included in the multi-environment GBLUP models. The predicted genetic value of each individual included in the GBLUP models for each trait in each environment was used with the GBLUP individual-by-marker allele frequency matrix to predict the genetic effect of each marker allele for each trait in each environment. A portal was then developed on BIMS to host this vector of marker effects and enable new users to upload tables of new individual-by-SNP marker data for the loci used in the original GBLUP model. Predictions for the new individuals are produced by multiplying the new sample-by-marker frequency matrix by the vector of predicted allelic effects. Predictions of the new material for each trait across environments are delivered alongside predicted performance of publicly available genetic material to enable comparison and evaluation of reliability of predictions. The use of this portal is demonstrated with genome-wide SNP genotypic data collected on new apple selections evaluated for an Australian genetic improvement program.
Assocaite Professor in quantitative genetic s and tree breeding of horticultural and forestry crops with particular foci on multi-variate mixed linear models, G-by-E, genomic prediction, multi-trait selection, modelling breeding strategies, conservation genetics, low-cost genotyping... Read More →
Many states in the US produce raspberries, however, most of the production is concentrated in three states: California, Oregon and Washington as most raspberry cultivars grow best in regions with cool summers and mild winters. However, newer raspberry cultivars have been developed exhibiting heat tolerance. Cultivars with heat tolerance provide an opportunity for the growers in the Southern states to include raspberries in their crop production. Local Mississippi growers are interested in incorporating raspberries into their productions. However, there lacks research-based recommendations on raspberry cultivars suitable for Mississippi's climate. The objective of this study was to evaluate raspberry cultivars in terms of plant growth, heat and cold tolerance, pest and disease resistance, berry yield, quality, and fruiting season to identify the best-suited cultivars for Mississippi. This experiment was conducted in a randomized complete block design with two types of fertilizer: conventional and organic. Data collection included measurements of plant growth and performance, berry yield and quality and fruiting season. The results showed that raspberry yield, single berry weight and fruit size were influenced by fertilizer treatment. The soluble solid contents, acidity, and fruit color were not influenced by fertilizer treatment. Raspberry yield was higher for “Polka”, “Encore”, “Heritage”, and “Latham” under conventional fertilizer. Cultivars “Himbo”, “Prelude”, ‘Bp1”, and “Encore” treated with conventional fertilizer had higher single berry weight. The average fruit size of cultivars “Prelude”, “Himbo”, “Encore”, “Bp1” treated with conventional fertilizer produced larger fruits in comparison to the other cultivars. The fruit's soluble solid content was highest in “Heritage”, indicating a sweeter taste. Cultivars “Polana” and “Anne” produced fruits with the highest acidity, indicating a tarter taste compared to other cultivars. Fruit color varied between cultivars, with differences in lightness, redness, and yellow coloration.
Hello! I'm passionate about the world of horticulture and am eager to explore and discuss various opportunities within the industry. I am particularly interested in pursuing a PhD in horticulture, with a specialization in either specialty crops or ornamentals. Additionally, I have... Read More →
The performance of kiwifruit, primarily gold-fleshed cultivars, has been evaluated for many years in central Alabama, with the earliest plantings occurring at the Chilton Research and Extension Center, Clanton, AL in the mid-1990s. The objective of this study was to determine bloom times of female and potential male pollinizers, appropriate harvest times, and fruit quality attributes of ‘AU Golden Dragon’, ‘AU Gulf Coast Gold’, and ‘AU Golden Sunshine’. The female cultivar ‘AU Golden Dragon’ blooms earlier than other cultivars evaluated and had good bloom overlap with the male cultivar Hortkiwi ‘Meteor’. The female cultivars ‘AU Golden Sunshine’ and ‘AU Gulf Coast Gold’ bloom approximately 2 weeks after ‘AU Golden Dragon’ and had good bloom overlap with the male ‘AU Golden Tiger’. The harvest period in central AL for each cultivar based on flesh color (hue
The increasing demand for tree fruit production necessitates optimizing nutrient balance in intensified orchard systems to maximize profits efficiently. While peach growers are advised to follow Extension and recommended guidelines for fertilization, such recommendations may not align with orchard-specific variables and environmental conditions. As a consequence, crop sufficiency ranges may require updating to reflect modern growing practices and environmental factors. Although leaf nutrient analysis is the most reliable method for diagnosing tree nutritional status, the prevalence of annual fertilizer application, driven by the low cost of fertilizers relative to crop value, often leads to excessive fertilization in peach orchards. Consequently, our objective was to evaluate established sufficiency levels and leaf analysis as tools for determining the need for annual fertilizer applications. To achieve this, we implemented a two-year study involving two fertilization programs in an orchard with three rows of 17 peach trees: two rows adhered to grower standard, annual fertilization, while the remaining row followed a rational fertilization program. The latter implied applying fertilizer only when leaf analyses indicated nutrient concentrations below established sufficiency thresholds for peaches. Leaf analyses were conducted annually in July, and if nutrient concentrations were within or exceeded sufficiency thresholds, no fertilizer was applied postharvest or the following spring. If nutrient concentrations fell below sufficiency thresholds associated with a significant difference in yield and fruit quality between the two programs, fertilization occurred in late summer and during bloom time the following spring. We assessed tree quality and productivity by measuring yield (total weight of all the fruit per tree) and fruit quality (size and brix) annually. The results of the first year showed that despite deficient leaf nitrogen and phosphorus concentrations and other nutrients such as potassium, calcium, and magnesium remaining within or above their sufficiency ranges, we observed no significant differences in yield or fruit quality between trees subjected to rational and standard fertilization practices. Consequently, fertilization for the upcoming year was deemed unnecessary in trees following the rational program. The outcomes of this study are expected to guide peach growers in making informed decisions based on updated data, reducing the environmental impact of overfertilization, which is inefficient for fruit production and uneconomical, and enhancing farm profitability.
Fruit shape variation is abundantly present in horticultural crops. This variation is critical to highlight the market class as well as the culinary purpose of the produce. Many of the underlying genes have been cloned in tomato, offering insights into the molecular mechanisms of morphological diversity. Specifically, members of the OFP, TRM and SUN family regulate produce shape variation in tomato and other crops, thereby highlighting the importance of these three families in regulating phenotypic diversity. Despite the knowledge of the genes, mechanistic insights into the function of members of these three gene families are lacking. Our research on the tomato genes OVATE and OFP20 has shown that changes in produce shapes are noticeable early in the development of the flower. Cell counts in ovaries at anthesis implied that changes in cell division patterning may underlie morphological diversity. However, gene expression studies showed that morphological changes were associated with cell wall processes and not with changes in cell division patterning.
In addition to botanical names, at least a dozen distinct categories of nomenclature are applied to plant cultivars, including various forms of cultivar denominations, breeders references, and trade names. Two sets of rules, the International Code of Nomenclature for Cultivated Plants (9th ed., 2016), and the Explanatory Notes on Variety Denominations Under the UPOV Convention (2022) provide current guidelines for plant cultivar nomenclature. In some instances UPOV and ICNCP rules differ, and stakeholders may wish to consider whether it would be feasible to seek harmonization, and the mechanisms by which that might be achieved. This session will trace a brief history of cultivar denomination rules for U.S. plant patents. The United States Patent and Trademark Office, which issues plant patents, does not provide detailed nomenclatural guidelines. In the past two decades a new model for plant nomenclature has prevailed, in which an alphanumeric code serves as the official cultivar denomination, and this is paired with a trademark, either registered or unregistered. The relationship between cultivar denominations and trade names can be complex and fluid. As co-editor of the Register of New Fruit and Nut Cultivars, the presenter professionally researches all new pomological cultivar denominations and trade names, to avoid publishing names that conflict with previous names or nomenclatural standards. The establishment of an official cultivar denomination has important practical consequences that are sometimes ignored by breeders and rights owners. When a cultivar has been granted a plant patent or plant breeders’ rights, the cultivar denomination recorded by the statutory plant registration authority that issues the grant becomes officially established (a “statutory epithet”), and cannot be casually changed or replaced by the rights owner. When such informal synonyms are used, they are best regarded as trade names, often as unregistered trademarks. Common mistakes and pitfalls in nomenclature are described.
Seven-year Yield and Fruit Quality Comparison of Four Apple Cultivars Between Tall Spindle and Bi-axis Systems in Western New York - Brian Lawrence After Avery: Apple Photosynthesis and Evidence of a Changing Environment. A Historical and Technical Evaluation - Curt Rom The Biological Mechanism Behind Early and Late Apple Sports - Alexander Engelsma Characterizing Unique Apple Selections for U-Pick Growers in the Midwest Using Descriptive Analysis, Consumer Liking Tests, and Phytochemical Analysis - Lydia Balogh Selection and Patenting of New, Grower Friendly Apple Trees by the Maryland Tree Architecture Project - Chris Walsh Effects and Interactions of Water Stress and Rootstock on Physiological Responses and Ambrosia Beetle Colonization of Apple Trees - Melissa Munoz The Role of Photosynthesis in the Regulation of Early Fruit Growth of Apple - Bayleigh Roussel
Increasing orchard planting density has helped improve grower profits and yields but establishment costs can be high. It is believed that by using bi-axis trees the number of trees required during planting can be reduced while possibly improving yields and fruit quality. To test this possibility, an orchard of four cultivars (‘Brookfield Gala’, ‘Aztec Fuji’, ‘Honeycrisp’, and ‘Ruby Mac’) was established and trained to either Tall Spindle (TS) or Bi-axis (BA) at 1m x 4m spacing. After the third year of growth, all TS trees and half of BA trees were summer hedged, resulting in three systems to compare: 1) TS hedged; 2) BA hedged; and 3) BA non-hedged. Measurements of trunk cross sectional area (TSCA), phenology, yield, and fruit quality were recorded for seven years to calculate cumulative values. At the end of the study, TSCA was larger on TS trees compared to hedged or non-hedged BA trees across cultivars. Biennial bearing was lower with ‘Brookfield Gala’ and ‘Aztec Fuji’ compared to ‘Honeycrisp’ and ‘Ruby Mac’ and trended lower on hedged or non-hedged BA trees than TS trees. The hedged or non-hedged BA trees had higher cumulative yields compared to TS trees across cultivars. Fruit size was reduced on hedged or non-hedged BA trees compared to TS trees, but all three systems had similar fruit color, firmness, and soluble solids on average. After seven years, there was no obvious benefit of using hedged or non-hedged BA systems to improve fruit quality, but higher yield from BA trees over TS trees when planted at the same density, regardless of hedging during the summer, was achieved. We calculated that BA trees could be planted at 15% lower planting density than TS trees to achieve the same yield.
In 1977 Avery published a review of apple leaf photosynthesis (Pn) rates to estimate maximum rates with current technologies and conditions. This presents a recent review of more than 90 published reports of apple photosynthesis from 1978-2022 evaluated the techniques and equipment used, the experimental parameters of CO2, temperature, light, and vapor pressure deficit. The goal of the review was to determine if techniques used reflected changes in global atmospheric [CO2], and if there was evidence of response of apple leaves to changing [CO2] with time. Avery in 1977 estimated mean apple Pn rate to be ca. 14 µgCO2m-2s-1 and a maximum rate of ca. 22 µgCO2m-2s-1. The current review suggests an estimated mean apple Pn rate to be ca. 15.6 µgCO2m-2s-1 , similar to Avery, but a maximum rate of ca. 31-35 µgCO2m-2s-1, higher than Avery. Since 1977, there has been an approximately 26% increase in global CO2. There was no correlation between experimental [CO2] or atmospheric [CO2] and reported Pn, and although reported Pn rates tended to increase with time, there was no significant correlation to time. Experimental[CO2] was reported in 58% of the reports but omitted in others. Experimental parameters of measurement temperature or vapor pressure deficit were commonly not reported.
Somatic mutations in apple commonly develop into viable bud sports for cultivation. When an apple bud sport has a desirable attribute such as improved color, size, shape, flavor, firmness, sweetness, or harvest timing, it has potential to be introduced as a new cultivar that growers utilize, and consumers enjoy. The genetic mutations and related mechanisms associated with early or delayed maturation (respectively resulting in early or late harvest date) in apple sports are not known despite their value to the industry. By acquiring knowledge about these genetic mutations and their respective molecular mechanisms, breeders can identify markers to conduct more informed crosses to select for early or late maturing apple lines. Apple lines with differing developmental rates resulting in differing ‘designed’ harvest windows would optimize the deployment of field laborers for the apple harvest and improve use of cultural practices to influence harvest time. Comparison of physiology-based markers of fruit developmental stages for apple sports with different maturation dates has been done, but, to the author’s knowledge, not on trees for which crop load has been appropriately adjusted to eliminate its effect on developmental rate. In this study, crop load was regulated on 6 different apple cultivars according to tree trunk cross-sectional area. The sports selected were the ‘Gala’ sport ‘Autumn Gala’ also known as ‘Harry Black’, the early maturing ‘Fuji’ sport ‘September Wonder Fuji’, and the early maturing ‘Cripps Pink’ (‘Pink Lady®’) sport ‘Maslin Cripps Pink’. These three sports were compared to their progenitor/standard harvest time cultivar. Apple fruits were measured on each of five trees per cultivar, and volumetric growth rate was analyzed. We found that in each comparison, fruit growth rate of the early variant was significantly greater early in fruit development, roughly coinciding with the expected conclusion of the cell division phase based on phenology. Consequently, a narrower window of genetic events responsible for the early or late harvest timing phenotype has been captured. Our work confines the search for genetic events responsible for the harvest date mutations to the early developmental stages for apple fruit. We propose that harvest date in these apple bud sports is physiologically predetermined from the very early stages of fruit development and very likely not a function of strictly ripening-related processes.
Dr. Randolph Beaudry, Professor, MSU Department of Horticulture (MSc, PhD, University of Georgia). His appointment is 50% MSU Extension and 50% AgBioResearch. His research program includes both regional and international projects and focuses on the physiology of plant responses to... Read More →
Thursday September 26, 2024 10:30am - 10:45am HST
South Pacific 2
The apple U-Pick market in Ohio lacks diversity in varieties to meet consumer demand outside of those typically available at grocery stores. Apple growers want new cultivars that are suited for growth in the Midwest, ripen across the picking season, and intrigue customers with unique flavors, textures, and traits. These diverse and unique tasting apples exist, but it is difficult to market these apples without a comprehensive understanding of the traits and consumer desirability of these fruits. This project aims to identify and characterize sensory traits in 33 up-and-coming apple selections including commercial, in-development, and wild varieties with novel characteristics suited for local production. Apple selections were chosen in conjunction with apple specialists at The Ohio State University and local apple growers. Consumer perception and apple traits were evaluated through two sets of sensory experiments: consumer hedonic testing and descriptive analysis. Consumer testing was conducted in private sensory booths, where apple slices were provided in a randomized, blinded order to mitigate order effects. One hundred participants rated apples on their appearance, texture, flavor, and overall liking on a 9-pt hedonic liking scale (i.e., dislike extremely to like extremely). Descriptive analysis was conducted by 12 trained panelists who used references as anchors on a 10-pt scale to score important appearance, aroma, flavor, and texture fruit characteristics. Measured characteristics were decided in collaboration with the panel organizer, trained panelists, and included traits of particular interest to growers. The trained panelists rated 26 traits like red color, floral notes, sweetness, and crispness. Anchors were carefully selected to provide precise references along the scale, such as sucrose solutions of varying concentration to calibrate judgements of sweetness. To compare how different factors of the apple related to each other, correlation analyses were run on the datasets. Flavor liking had the strongest positive correlation with overall liking, followed by texture liking, while appearance liking showed a weaker positive correlation. Sweetness exhibited a slight positive correlation with overall liking, whereas sourness showed the opposite. Using mean separation tests, we identified 15 apple selections liked equivalently to Honeycrisp, a top commercial apple. Further phytochemical analysis will enable gaining insights on nutritional quality profile and its relation to consumer preference. Our goal is to provide information on novel apples that will enable apple growers to diversify their offerings, which will also benefit producers and consumers.
The Maryland Tree Architecture Project (MD-TAP) used classical plant breeding methods to create, identify, select and then patent grower-friendly apple trees. The project began in 1991 with the open pollination of 'McIntosh Wijcik' trees set in an isolated 'Gala' block. Elite seedlings resulting from that initial cross then served as male parents in an open-pollination of commercial cultivars well-adapted to the warm, wet, windy, Mid-Atlantic climate. Two scion-dwarfed, apple trees producing good quality fruit and demonstrating a reduced susceptibility to fire blight resulted from this effort. These two selections were patented as 'MD-TAP1' and 'MD-TAP2' in 2023. A replicated field trial was set in 2016 to compare these two scion-dwarfed selections, with their wild-type siblings also from this program. Trees were budded onto 'M.111,' a semi-dwarfing rootstock to assess their growth habit and tree size without the benefit of trellis support or sustained annual pruning. Trees were set at a 2.75 by 4.25 m (9 by 14 ft) spacing and are still manageable. Despite annual pruning, they are similar in height to trees in an adjacent tall-spindle planting budded onto dwarfing rootstocks. The University of Maryland concluded two Materials Transfer Agreements (MTAs) with other universities before the patents were allowed. After patenting, the University began contacting commercial nurseries in the Mid-Atlantic Region for future testing and licensing.
Chris Walsh is a Professor Emeritus in Horticulture. He currently maintains research and educational programs in tree fruit production and apple tree breeding, and in fresh-market produce safety.
Thursday September 26, 2024 11:00am - 11:15am HST
South Pacific 2
Rapid apple decline (RAD), a phenomenon that causes sudden decline and death of young apple trees in high-density orchards, is a pressing issue. This problem has been associated with abiotic (flood, drought, freeze) and biotic stressors (fungi, bacteria, and insects). Ambrosia beetles (AB) (Xylosandrus spp.) have been linked to stressed trees suffering from RAD. However, the direct association is still not clear. We evaluated the effects and interactions of rootstock (‘B. 9’, ‘M. 7’, and ‘G. 41’) and water stress (flood, drought, control) on physiological responses and AB colonization. Specifically, a greenhouse experiment was performed in spring 2023 on 14-month-old potted ‘MAIA1’ trees. Trees were subjected to water stress for 20 d. Water stress treatments consisted of a saturated pot-in-pot system for flood, water with-held for the duration of the experiment for drought, and irrigation based on soil moisture, maintaining the pots between 0.7 and 1 water fraction volume for control trees. The experiment had a randomized complete block design, was replicated 10 times, and had a factorial treatment structure. Measurements were made every 2 d for soil moisture, fluorometry, and spectrometry data, every 4 d for leaf gas exchange and midday water potential, at 7 and 14 d for ethanol volatiles, and at the termination of the experiment for AB colonization. Under control conditions, ‘G. 41’ trees had higher transpiration, stomatal conductance, and assimilation rates than ‘B. 9’ and ‘M.7’ trees. However, after 4 d of stress, ‘G. 41’ showed a more rapid decline in leaf gas exchange parameters relative to other rootstocks. Drought-stress trees from the three rootstocks declined 4 d faster than flood trees during the first 12 d. However, this decline occurs more abruptly in ‘G. 41’ and ‘M. 7’ trees. From 16 to 20 d, drought and flooded trees have a similar response. Under control conditions, all three rootstocks have similar quantum efficiency values. Conversely, under water stress, ‘G. 41’ and ‘M. 7’ declined faster than ‘B. 9’ trees, with a more severe response to drought for ‘G. 41’ and ‘M. 7’ trees. Chlorophyll index (Ci) showed lower values for flood and drought trees after 10 d for ‘G. 41’ and ‘M. 7’ trees. For ‘B. 9’, this was only true in drought trees. Flooded trees had AB tunnels three times longer than control, and drought trees were the only ones where AB larvae were observed, which was linked to higher ethanol levels.
Photosynthesis is well-known to not only occur in leaves but also other tissues like stems, sepals, and fruits. Fruit photosynthesis has been documented in cucumber, tomatoes, satsuma mandarins, prickly pear, wheat, and apple. Fruit photosynthesis occurs in these instances not only to contribute to carbon assimilation but to support other metabolic processes, the synthesis of metabolites, and seed development. Early fruit growth in apple is regulated by energy-intensive cell division that lasts for approximately five weeks before switching to a phase of predominantly cell expansion-driven growth. Thus, fruit photosynthesis during early fruit development in apple could function to fulfill the resource and energy requirements necessary for the growth and development of fruit tissues. To examine this potential contribution of photosynthesis to apple fruit metabolism, shade bags made of 30%, 65%, and 80% shade cloth were placed on fruitlets at 16 days after full bloom. The effects of fruit shading on fruit tissue plastid ultrastructure, metabolite composition and tissue transcriptomes were analyzed. Using transmission electron microscopy (TEM), we found that plastids in the peel and cortex overall resembled that of photosynthetically active plastids; they contained stromal and granal thylakoids similar to those found in leaves. Spatially, pith plastids displayed unique hypergranal features , with increased granal thylakoids and a significantly reduced presence of stromal thylakoids. When compared to the control, 80% shaded peel plastids contained more plastoglobuli, and 80% shaded pith plastids displayed prolamellar bodies, which are indicative of disassembly. Further, significantly lower chlorophyll a concentration was observed in shaded fruit. Metabolite analyses indicated that sorbitol was significantly greater in shaded fruit than in the control. Transcriptome analyses indicated substantial changes associated with carbohydrate metabolism in the fruit cortex and peel in response to fruit shading. Together, these analyses indicate a significant contribution of fruit photosynthesis to early fruit growth and development in apple.
Six -year Performance of Semi-dwarfing Peach Rootstocks From the NC-140 'Cresthaven' Trial in Western Colorado - Jeff Pieper Nutritional Dynamics and Horticultural Performance of Peach Orchard in the United States in Response to Different Soil Amendment Programs. - Ayodeji Idowu Influence of Low-, Medium-, and High-Chill Requirement Rootstocks on the Metabolomic Profile of Low-Chill Peaches - Jonathan Clavijo Herrera Effects of plum tree architecture on canopy light environments and fruit quality - Lisa Tang Does the Utah Model Still Work in Utah? Evaluation of Existing Phenological Models for Tart Cherry in a Changing Climate - Josette Moon A Mobile Cartographer System to Measure Tree Growth Within Tart Cherry Orchards - Brent Black Enhancing Uniformity in Tart Cherry Orchards Through Precision Management and Variable Rate Fertilization - Kurt Wedegaertner Tree temperature prediction to improve chill accumulation estimation in cherry under climate change - Giulia Marino
Eight rootstock cultivars were planted in 2017 as part of the NC-140 semi-dwarfing peach [Prunus persica (L.) Batsch] rootstock trial. The eight rootstock cultivars were budded to ‘Cresthaven’ and examined for their potential use in Western Colorado high density production systems. Listed in order of declining vigor the rootstocks included ‘Guardian®’, ‘Rootpac® 20’, ‘Lovell’, ‘ControllerTM 8’, ‘ControllerTM 6’, ‘Rootpac® 40’, ‘ControllerTM 7’, and ‘MP-29’. One rootstock, ‘ControllerTM 7’, was unable to perform in alkaline soils, showing extreme iron chlorosis and diminutive fruit size. Deemed unsuitable for use in Colorado, this rootstock was removed from analysis in the 3rd leaf. Six years of data showed that all remaining rootstocks, except ‘MP-29,’ had vigor profiles within 14% of ‘Lovell’, a known standard, making them attractive candidates for use in high density production. The two ‘Rootpac®’ rootstocks performed contrary to previous reports. ‘Rootpac® 20’ was the second most vigorous and ‘Rootpac® 40’ was the third least vigorous, slightly larger than ‘ControllerTM 6’. Additional physiological traits showing distinct differences between the rootstocks were yield, proleptic shoot formation, light interception, fruit size, and internal fruit quality. In the six years since planting there have been three harvests. Cumulative yield showed a strong linear relationship to vigor (TCSA). ‘ControllerTM 6’ had early precocity and high yields given its vigor class. Observance of gummosis was also positively associated with vigor. Both vigor and proleptic shoot formation manipulated the canopy light environment. ‘ControllerTM’ series rootstocks had increased proleptic shoot formation. Vigor-limiting rootstocks had increased light availability in the canopy leading to enhanced dry matter content and soluble solid concentration. Cumulative fruit size and weight showed ‘Rootpac® 20’ had the heaviest, and ‘ControllerTM 6’ the largest, fruit size. ‘MP-29’, the most dwarfing rootstock produced smaller fruit on average; however, fruit size was still commercially acceptable.
Compost, mulch and manures have been reported as a potential substitute for synthetic fertilizer in fruit orchards, can improve soil health as well as increase the sustainability of orchard systems. In this study, we compared two rates (10 tons/acre as compost 1x and 20tons/acre as compost 2x) of pre-plant incorporation of food waste compost (FWC) and growers’ standard rate of inorganic/chemical fertilizer (control) of a replanted and virgin peach orchards in South Carolina. Measurement includes soil health indicators such as soil nutritional status and macronutrient dynamics, yield, and fruit quality (specifically on the incidence of diseases and physiological disorders). We hypothesized that the pre-plant incorporation of organic matter with subsequent topical application would improve soil moisture and nutrient availability, increase yield, and enhance the quality of marketable fruits. Higher cation exchange capacity and buffering capacity was recorded in soil treated with FWC than in the control treatment. In the replanted orchard, the 2x treatment resulted in improving soil health indicators such as SOM, cation exchange capacity, phosphorus, soil infiltration, and soil moisture, but not in the virgin orchard compared to the control treatment. Soil extractable P was higher in the FWC treatment as compared to the control treatment, while the soil extractable K ranges from high to excessive K across all treatments. No significant difference between the yields from both orchards. However, we observed numerical differences in the yields of the 2x treatment compared to the 1x and control treatments. Our results show that the yearly application of compost provides the orchard’s nutritional requirement, increases yield, and lower disease pressure in both orchards compared to the control treatments.
Graduate Research & Teaching Assistant, Clemson University
I am an adept third-year Ph.D. student working on improving soil health and ecosystem conservation through rigorous enhancement of soil organic matter and strategic soil nutrient management for agricultural and environmental sustainability. To achieve this, I am testing different... Read More →
Rootstocks are widely used for commercial orchard establishments throughout the world, as they facilitate scion adaptation to challenging edaphic and environmental conditions, as well as mitigate the impact of pests and diseases. Furthermore, rootstocks may influence physiological, biochemical, or phenological processes in the scion. Nevertheless, little is known about the influence of rootstocks on metabolomic profiles of Prunus scions, particularly in low-chill cultivars. This study aimed to determine the influence of rootstocks with varied chilling requirements on the metabolomic profiles of low-chill peaches. Scion ‘UFSun’ was grafted on low-(Flordaguard), medium-(P-22), and high-(MP-29, Guardian, and Nemaguard) chill requirement rootstocks, and grown in a greenhouse in Gainesville, Florida. Vegetative tissue samples were collected for extraction of metabolites. Untargeted compounds were analyzed using an Orbitrap Fusion Tribrid mass spectrometer system, interfaced with an automated A VanquishTM UHPLC system, and a total of 152 metabolites were detected. Potential differences in metabolomes associated with the rootstocks were analyzed by performing a partial least square–discriminant analysis (PLS-DA), although it was not possible to determine group differences when comparing all treatments. An orthogonal PLS-DA approach supported by permutational MANOVA test was implemented for paired comparison of plants grafted on Flordaguard (rootstock recommended for commercial production in Florida) vs. all other rootstocks, and differences were observed for all comparisons. For further confirmation of these results, and determination of the metabolites potentially differentially expressed due to rootstock influence, the Empirical Bayesian Analysis of Microarrays (EBAM) approach was implemented, as adjusted for analysis of metabolites in MetaboAnalyst 6.0. A total of 85, 52, 0, and 61 metabolites were dimmed as potentially differentially expressed when comparing trees grafted on Flordaguard vs. P-22, MP-29, Guardian, and Nemaguard, respectively. Most of these metabolites may be flavonoids, phenylpropanoids, and polyketides. According to our observations, low-, medium-, and high-chill rootstocks can influence the metabolomic profile of low-chill scions.
In the orchard production system, upright or pillar trees with vertical branch orientations have narrow architecture profiles and therefore can be suited to high-density planting to increase productivity. In plum (Prunus domestica), there are natural variations of tree forms that range from upright to more horizontal growth habit. Recently, researchers at the USDA-ARS Appalachian Fruit Research Station demonstrated that silencing TILLER ANGLE CONTROL 1 (TAC1) via RNA interference (RNAi) in ‘President’ plum led to pillar tree forms with upright lateral shoot growth, whereas silencing LAZY1 in ‘Stanley’ plum resulted in outward shoot orientations and weeping tree shape. The objective of this study was to assess the effects of tree architectures on canopy light availability and fruit quality using field-grown mature (7-year-old) TAC1 and LAZY1 silenced plum trees in comparison with their respective non-transgenic counterparts as controls. Our results indicated that slender canopy profiles due to silencing of TAC1 allowed significantly greater light availability without negative impacts on fruit size, soluble solids contents, or titratable acidity compared to non-transgenic plum with the same genetic background. Additionally, skin color of fruit was more uniform in TAC1-RNAi lines than in standard-shaped control trees, suggesting a positive correlation between canopy light distribution and fruit coloration in association with upright branch orientations. In contrast, light availability in LAZY1-RNAi tree was reduced significantly by over 50% compared to the control. Although there is no difference in fruit size, soluble solids content in fruit of the LAZY1-RNAi plum than that of the non-transgenic counterpart.
Phenological models use local temperature data to predict spring flower bud development and guide management decisions in temperate fruit crops. In high elevation continental regions such as the U.S. Intermountain West, changing climate brings more extreme temperature variability resulting in increased risk of spring freeze damage. We evaluated bloom dates of tart cherry (Prunus cerasus L. ‘Montmorency’) in a high elevation continental climate (1327 to 1484 m elevation, Utah) to test the validity of 50-year-old phenological models under current climatic conditions. Mature commercial tart cherry blocks were selected in proximity to existing weather stations (climate.usu.edu, FGNet). Bud stages were observed weekly in April and May of 2019 through 2023 with 3 to 8 locations monitored per year. Observed stages were compared to Utah Standard and Modified prediction models. Prediction error varied with year and stage of development, where 2023 bloom was on average 3 days earlier than predicted, compared to 2020 when bloom was 6 days later than predicted. Modern weather stations provide more detailed climatic data (hourly temperature, light, humidity, wind speed), and the opportunity to refine and improve existing models. Improved model reliability would provide better decision support for increasingly expensive freeze protection measures.
Temperate orchard sites have highly variable soils that contribute to uneven tree growth, providing a unique setting for precision management efforts. Precision management seeks to map spatial variability and implement variable rate management to optimize inputs. The objective of this study was to develop a platform for simultaneous measurement of tree growth and size to facilitate the enhancement of precision management practices in tart cherry (Prunus cerasus) orchards. Measurements included: canopy light interception; canopy height, volume, and width; and trunk cross sectional area (TCSA). Light interception (ceptometry) was by 15 30-cm line quantum sensors recording PAR at 0.6-second intervals, positioned on a UTV-mounted boom that passed under the canopy. Light interception was calculated based on data from a reference PAR sensor placed outside the orchard. Canopy height, width and volume of individual trees were measured using a side-scan LiDAR system mounted to the same UTV that generated point-cloud maps of each orchard row. These canopy measurements were then compared to point-cloud maps generated from aerial visual imaging (UAV). TCSA was estimated using a stereovision depth camera that captured paired visual spectrum (RGB) and point-cloud images, that were then aligned and segmented for individual tree trunks. Using pixel depth data, trunk widths for individual trees were estimated. The platform and associated sensors were used to map four commercial tart cherry orchard blocks (8-10 ha) located near Santaquin, Utah, USA, during the 2023 (ceptometry and UAV, only) and 2024 seasons at 2-week intervals. During the 2023 season, 8 ceptometry maps were generated with corresponding UAV-based maps. Side scan lidar data for 1 map of canopy height, width, and volume were collected in each of the 4 orchards, along with data for 1 TCSA map. Preliminary analysis shows strong spatial agreement among mapping techniques, indicating that the technologies are well suited to precision orchard management. Data for 2024 will also be presented, with multi-season tree growth analysis.
Tart cherry (Prunus cerasus) orchard sites are often chosen for favorable microclimates, and consequently exhibit highly diverse soil conditions that result in non-uniform tree growth and yield potential. There is increasing interest in utilizing precision management techniques to map tree vigor and implement variable rate management to optimize inputs and enhance uniformity. The objective of this study was to assess the variability of soil and canopy characteristics and implement prescription fertilizer rates based on the mapped variability. The study was conducted on four mature (18-22 years) commercial tart cherry orchard blocks (8-10 ha) located near Santaquin, Utah, USA. Soil variability maps for each orchard were generated through soil sampling, guided by surveying apparent electrical conductivity (ECa) using an electromagnetic induction meter. Spatial variability in tree vigor was quantified using satellite imagery provided by Simplot Smart Farm® Permanent Crop Analysis. Prescription fertilizer rates, derived from the variability maps, were applied to each block in the spring/summer of 2023 and 2024, which included granular fertilizer applied as a single application or as split applications based on each prescription map. Tree response to the prescription treatments were monitored every two weeks using a novel platform capable of mapping plant growth parameters including canopy height, volume, width, and density; and trunk cross sectional area (TCSA). By monitoring growth parameters within this timeframe, we were able to comprehensively evaluate within-seasonal fluctuations in growth. Soil sampling revealed significant correlations between ECa and soil texture. Preliminary results indicate significant within-orchard variations in mid-season tree vigor, that are also correlated with long-term growth characteristics (canopy size and density). Both long-term and short-term growth measures are also closely correlated with soil ECa (i.e. texture). The effect of variable fertilizer application within this soil texture variability will be discussed, offering insight into the effectiveness of precision management techniques in mitigating variability within tart cherry orchards.
Timing application of dormancy breaking products is essential for adequate bloom and yield in cherry. Available temperature-based chill accumulation models often fail to predict correct spray timing, particularly during years with unusual temperature patterns recently driven by climate change. One potential cause for the unreliability of the current models is their dependence on a single climatic variable, air temperature, to estimate the impact of weather on tree physiological processes. We hypothesized that using tree temperature, rather than air temperature, will increase the accuracy in predicting chill accumulation, especially in warm and sunny winters. Hence, our objective was to develop a framework to predict cherry tree temperature based on easily available environmental data. For three consecutive seasons and in three commercial cherry orchards across California, including the southernmost US cherry production region, we measured main climatic parameters at half hour intervals. At the same time, we monitored tree temperature with T-type thermocouples inserted below the bark of main branches. We developed predictions of tree temperature as a function of meteorological variables obtained from public weather stations using generalized additive models. Trees were, on average, 10 ºF warmer than the air during clear days, with differences being up to 20-25 ºF. Tree chill accumulation was about 8-12 chill portions lower than air chill accumulation. The difference was year- and site-specific, reflecting the importance of including diverse environmental parameters to estimate chill accumulation precisely. The ‘TreeChill model’ predicts tree temperature based only on environmental parameters easily achievable from public weather stations with a coefficient of determination of 0.956 resulting in only 0.4 chill portions difference between measured and predicted tree chill. This model will enable growers to implement tree temperature in their management decisions, including dormancy breaking agent applications, cultivar selection, pest control etc, increasing California cherry industry resilience to climate change. In the future, we plan to adapt the model to different crops and locations.
