(108) Early Flower Bud Production and Field Establishment of Two Pawpaw Cultivars on Five Seedling Rootstocks

Abstract

The pawpaw [Asimina triloba (L.) Dunal] is native to the southeastern United States and has potential as a new tree fruit crop. Clonal rootstocks are not currently available for pawpaw cultivars; therefore, nurseries graft cultivars onto rootstock derived from locally available seed. Great variation in rootstock vigor with this seedstock can result in grafted trees that lack vigor and have delayed fruit production. Pawpaw rootstocks that promote precocity would be desirable to growers. The objectives of this study were to determine if rootstock source and pruning system influenced precocity and field establishment of two pawpaw cultivars. In May 2004, a rootstock trial was planted at the Kentucky State University Research Farm that consisted of `Sunflower' and `Susquehanna' budded onto five seedling rootstocks (PA-Golden, Sunflower, Susquehanna, K8-2, and commercially available seed) with either a minimal or central leader pruning system. There were eight replicate blocks with each treatment combination, for a total of 160 trees. In Fall 2005, field mortality was greatest (58%) for `Susquehanna' budded onto Susquehanna seedling rootstock, whereas mortality was about 25% with other scion/rootstock combinations. The number of flower buds present on each tree was evaluated in Feb. 2006. Rootstock and pruning method did not influence the number of trees exhibiting flower buds. However, cultivar did influence the number of trees with flower buds; more trees of `Sunflower' (48%) had flower buds than `Susquehanna' (8%), and `Sunflower' (3.46) had more flower buds per tree than Susquehanna (0.43). Pruning system did influence the number of flower buds per tree; minimal pruned trees (2.65) had more flower buds per tree than central leader (1.21) trained trees.