ASHS 2024 Conference: Full Schedule

12:30pm HST

POM 2 - Testing Agronomic Strategies to Reduce Biennial Bearing in Apples

Wednesday September 25, 2024 12:30pm - 12:40pm HST

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.

Speakers

Thiago Campbell

Washington State University

Co-authors

Lee Kalcsits

Washington State University

Wednesday September 25, 2024 12:30pm - 12:40pm HST
Coral 2

Poster presentation (individual talk), Pomology 2

SUBJECT Pomology

12:40pm HST

POM 2 - Identifying Local Apple Germplasm for Use of Hard Ciders in North Dakota

Wednesday September 25, 2024 12:40pm - 12:50pm HST

Coral 2

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.

Speakers

Wenhao Dai

North Dakota State University

Co-authors

Brent Trela

Trelab

Mika Mzumara

North Dakota State University

Tian Sun

North Dakota State University

Zhao Jin

North Dakota State University

Wednesday September 25, 2024 12:40pm - 12:50pm HST
Coral 2

Poster presentation (individual talk), Pomology 2

SUBJECT Pomology

12:50pm HST

POM 2 - The Fruitlet Size Distribution Model As A Thinning Decision Aid For Precision Crop Load Management Of Apple

Wednesday September 25, 2024 12:50pm - 1:00pm HST

Coral 2

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.

Speakers

Laura Hillmann

Michigan State University

Co-authors

Luis Gonzalez Nieto

IRTA

Sara Serra

Washington State University

Stefano Musacchi

Washington State University

Terence Robinson

Cornell University

Todd Einhorn

Michigan State University

Tom Kon

North Carolina State University

Wednesday September 25, 2024 12:50pm - 1:00pm HST
Coral 2

Poster presentation (individual talk), Pomology 2

SUBJECT Pomology

1:00pm HST

POM 2 - Deciphering the Proline-Mediated Flowering Delay Mechanism in Peach through Physiological and Metabolic Analyses

Wednesday September 25, 2024 1:00pm - 1:10pm HST

Coral 2

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.

Speakers

HYUNSUK SHIN

Gyeongsang National University

Co-authors

JAE HOON JEONG

Gyeongsang National University

MUTHURAMALINGAM PANDIYAN

Gyeongsang National University

Seung Heui Kim

Korea National College of Agriculture and Fisheries

YEONJU PARK

Gyeongsang National University

Wednesday September 25, 2024 1:00pm - 1:10pm HST
Coral 2

Poster presentation (individual talk), Pomology 2

SUBJECT Pomology

1:10pm HST

POM 2 - Genetic Architecture of Important Traits for Prunus Crop Improvement

Wednesday September 25, 2024 1:10pm - 1:20pm HST

Coral 2

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.

Speakers

Michael Itam

Clemson University

Co-authors

Chun Huai Cheng

Washington State University

Dorrie Main

Washington State University

Jing Yu

Washington State University

Jodi Humann

Washington State University

Katheryn Buble

Washington State University

Ksenija Gasic

Clemson University

Ping Zheng

Washington State University

Sook Jung

Washington State University

Taein Lee

Washington State University

Wednesday September 25, 2024 1:10pm - 1:20pm HST
Coral 2

Poster presentation (individual talk), Pomology 2

SUBJECT Pomology

1:20pm HST

POM 2 - Taste Acidity and Other Important Fruit Characteristics of New Peach Varieties Compared with Concurrent Varieties During

Wednesday September 25, 2024 1:20pm - 1:30pm HST

Coral 2

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’.

Speakers

Hemant Gohil

Extension AgentII/Associate Professor, Rutgers Cooperative Extension

Co-authors

Daniel Ward

Rutgers University

POM2 POSTER GOHIL pdf

Wednesday September 25, 2024 1:20pm - 1:30pm HST
Coral 2

Poster presentation (individual talk), Pomology 2

SUBJECT Pomology

1:30pm HST

POM 2 - Role of Silicon in Peach Water Stress Tolerance

Wednesday September 25, 2024 1:30pm - 1:40pm HST

Coral 2

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.

Speakers

Noah Willsea

Clemson University

Co-authors

Inma Martos-Garcia

University of Cordoba

Juan Carlos Melgar

Clemson University

Maria Benlloch-Gonzales

University of Cordoba

Ricardo Fernandez-Escobar

University of Cordoba

Wednesday September 25, 2024 1:30pm - 1:40pm HST
Coral 2

Poster presentation (individual talk), Pomology 2

SUBJECT Pomology

1:40pm HST

POM 2 - Mechanization Reduces Pruning and Harvest Labor Time in the Cider Apple Orchard

Wednesday September 25, 2024 1:40pm - 1:50pm HST

Coral 2

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.

Speakers

Poster presentation (individual talk), Pomology 2

SUBJECT Pomology