published in Pomona in Fall 1996, which was reprinted again in Winter 1999. Here we will very briefly mention a few of our findings and where we are heading.

Seed germination, seed storage techniques, and clonal propagation methods have been examined through the research efforts of Dr. Kirk Pomper, Dr. Desmond Layne, Ms. Cynthia Finneseth, Ms. Snake Jones, Mr. Eddie Reed Jr., and Dr. Robert Geneve (University of Kentucky). We have developed recommendations for the optimal conditions to propagate pawpaws by seed; this information can be found in the extension publication, “Pawpaw Planting Guide: Cultivars and Nursery Sources,” which is available from KSU upon request or on the KSU pawpaw web site. We have found that some major points to remember about propagating pawpaws by seed are: 1) Never let the seed dry out; this greatly reduces the germination rate. Keep pawpaw seed in ziplock bags containing moist peat moss, and then store in a refrigerator until you are ready to use it. 2) Pawpaw seed has a chilling requirement that must be satisfied for optimal germination rates. You should store seed for at least 100 days in a refrigerator (in moist peat moss) for optimal germination. 3) Do not let pawpaw seed freeze, it will kill the seed. 4) Start seeds in tall pots (12”), as the seedlings have strong taproots. Since the roots of field dug pawpaw seedlings are easily damaged, we usually recommend starting pawpaws in pots, or buying them from nurseries in pots, and then transplanting them. 5) If you are growing seedlings outside, keep the plants in moderate shade their first year (we use 55% shade cloth) for maximum growth of the plant. Seedlings will grow well in whitewashed or even unshaded greenhouses.

In terms of clonal propagation of pawpaw, budding (specifically chipbudding), and grafting (whip-and-tongue) techniques are most successful on actively growing pencil thick seedling rootstock. Clonal propagation of pawpaw by other methods such as root cuttings or softwood cuttings has been unsuccessful in our laboratory. Attempts to propagate pawpaw via tissue culture have also not yet been entirely successful; however, we have been able to proliferate shoot buds in culture, although most of the buds do not elongate. Research continues on developing a tissue culture propagation system for pawpaw. Mound layering is also currently being investigated as an alternative clonal propagation technique.

Since 1995, KSU has served as the USDA National Clonal Germplasm Repository, or gene bank, for Asimina spp. (pawpaw), as a satellite site of the repository at Corvallis, OR. There are over 1,500 accessions (trees) from 16 different states that are planted on 8 acres at the KSU farm. Genetic diversity is a critical component of biodiversity and adjustment to the environment. We are attempting to evaluate the genetic diversity contained in wild pawpaw populations across its native range so that unique material can be added to the KSU repository collection; this rich potential source of useful genetic traits will be used in future breeding efforts. Drs. Hongwen Huang, Desmond Layne, and Donald Riemannschneider (USDA Forest Service, Rhinelander, WI) have used allozyme and isozyme marker systems to examine genetic variation in domesticated pawpaw cultivars and natural populations. These studies suggested that moderate levels of genetic diversity exist in both cultivated as well as wild populations; however, these previous studies included only a limited number of loci. Before leaving KSU, Dr. Layne received a USDA 1890s Capacity Building Grant to establish a molecular genetics laboratory at KSU. We can now extract DNA from pawpaw leaves and use it with techniques involving the polymerase chain reaction (PCR), with methods similar to those used by law enforcement agencies for DNA finger printing of potential suspects, in order to evaluate genetic diversity of the pawpaw populations. Using PCR-DNA based marker systems, higher rates of precision (larger number of loci) are possible in fingerprinting pawpaw cultivars and evaluating genetic diversity in pawpaw across its native range than with allozyme or isozyme methods used previously. Under the direction of Dr. Pomper, Ms. Tera Bonney (KSU graduate student) and Ms. Snake Jones (KSU Research Assistant) have collected over 500 pawpaw leaf samples from trees at a dozen sites in Kentucky and over 25 volunteers collected leaf samples from 270 trees in 17 different states in the pawpaw's native range for use in this study. We are currently processing the samples for use in our studies.