ASHS 2024 Conference

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.

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.

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.