2018 ASHS Annual Conference

Pawpaw (Asimina triloba), America’s forgotten tree fruit, is emerging as an alternative high-value niche crop for small farms in Kentucky. Some literature states that pawpaw is a cross-pollinated crop; however, there is evidence of self-compatibility in some varieties such as ‘Sunflower’. The objective of this study was to determine if the pawpaw cultivars Sunflower and Susquehanna display self-compatibility and if this impacts fruit set. Two pawpaw cultivars, ‘Sunflower’ and ‘Susquehanna’, were examined in this study at the Kentucky State University Harold R. Benson Research and Demonstration Farm. In total 1000 crosses, including 250 self and cross pollinations for each variety, were carried out with open flowers in April, 2016 and 2017; competing flowers were removed after pollination. In 2016, the number of fruit clusters and fruit per cluster were recorded on three dates: May 24th, July 22nd and August 22nd. Similarly in 2017, the data were recorded on: May 31st, June13th, and August 21st. The seeds from each treatment were extracted from the fruit and stratified (4⁰C) in wet peat moss for at least 110 days. The seeds from 2016, 20 of each self or cross, were then germinated in pots in a greenhouse. Young leaves of parent material and the newly germinated offspring were collected for DNA extraction. Primers for three pawpaw simple sequence repeat (SSR) for the loci Pp-B3, Pp-B103, and Pp-G124 with unique fingerprint patterns for each variety were selected for parentage confirmation. This is the first study to report DNA evidence supporting self-compatibility in pawpaw. The DNA fingerprinting results confirmed the occurrence of some self-fruit set in both ‘Sunflower’ and ‘Susquehanna’. Surprisingly, Susquehanna was found to exhibit greater self-compatibility compared to Sunflower based on the percentage of self-pollinated offspring. Although both cultivars served as pollinizers to each other; the ultimate fruit set seemed to have a direct relationship to the genetic yield potential of the maternal tree.

KEYWORDS: Horticulture, Pawpaw, Self-compatibility, New crops