Growth, yield and physiological behavior of size-controlling peach rootstocks developed in California

A collaborative research program between the University of California, Department of Pomology and the Fresno USDA Horticulture Crops Research Laboratory has identified several promising clonal, size-controlling rootstocks for California peach production. An ongoing production trial with two peach scion cultivars (Flavorcrest and Loadel) on five of these interspecific hybrid rootstocks (Hiawatha (open pollinated seedling of Prunus besseyi x P. salicina hybrid), K-146-43, K-146-44, P-30-135 (P. salicina x P. persica hybrids) and K-119-50 (P. salicina x P. dulcis hybrid), compared with Nemaguard (the California P. persica standard) has yielded very positive results. After six years in the orchard, trees on the five experimental rootstocks have reduced trunk circumferences (60-95% of trees on Nemaguard), reduced dormant pruning weights (22-80%), reduced summer pruning weights (40-80%) with acceptable fruit size and crop yields (54-98% of trees on Nemaguard.) An analysis of the relative efficiency of each scion/rootstock/training system, using a calculated modified harvest increment (annual fruit dry weight/annual pruning dry weight), indicated that trees on the size controlling rootstocks were more efficient in partitioning dry matter to crop than trees on the vigorous Nemaguard rootstock.