Seedling Rootstock Recommendations for Pawpaw (Asimina triloba)

The pawpaw [Asimina triloba (L.) Dunal] is the largest tree fruit indigenous to the United States, and is commercially produced on a small scale as a niche fruit crop. Pawpaws cannot be successfully propagated via cuttings, layering, or tissue culture, and clonal rootstocks are not available for pawpaw cultivars. Therefore, cultivars are grafted onto seedling rootstock of diverse genetic origin. Great variation in tree survival, scion growth, and fruit production are often observed. Pawpaw rootstocks that are vigorous, have a high survival rate, and promote precocity and high fruit yields would be desirable to growers. A field study was conducted to determine if survival, growth rate of scions, and fruit yield would vary by seedling rootstock source. Scions of the pawpaw cultivars Susquehanna and Sunflower were grafted onto rootstock derived from seedlings of ‘Sunflower’, ‘PA-Golden’, ‘Susquehanna’, the selection K8-2, and commercially available mixed seed (RVT). The rootstock trial was planted in 2004 at the Kentucky State University Research Farm in a randomized complete block design. Seedling rootstock derived from ‘Susquehanna’ and K8-2 had survival rates below 60% and are not recommended for use as a rootstock source. Early fruiting data indicated an influence of rootstock on fruit weight. In 2009, rootstock influenced fruit weight, with trees on ‘Sunflower’ and ‘PA-Golden’ -derived rootstock producing larger fruit (226 and 235 g, respectively) than those on K8-2-derived seedling rootstock (176 g). Rootstock did not significantly influence trunk cross sectional area, number of flowers, fruit set, number of fruit, yield, or yield efficiency.