GENETICALLY DIVERSE PEACH SEEDLING ROOTSTOCKS AFFECT LONG-TERM PERFORMANCE OF REDHAVEN PEACH ON FOX SAND

Ten genetically diverse peach [Prunus persica (L.) Batsch] seedling ro otstocks were studied for 10 years on Fox sand using 'Redhaven' as the scion. The purpose of the experiment was to assess the performance of three Harrow Research Station (Ont.) hybrid selections (H7338013, H73 38016, and H7338019) and two northern China introductions ('Chui Lum T ao' and 'Tzim Pee Tao') against five commercial standards, two of whic h were selected in Canada ('Harrow Blood' and 'Siberian C') and three in the United States ('Bailey', 'Halford', and 'Lovell'). Rootstock pe rformance was assessed indirectly by measuring or subjectively rating various aspects of scion performance including annual trunk cross-sect ional area (TCA); final tree height, spread, and TCA; bloom and fruit set intensity; yield and yield efficiency; canker (Leucostoma spp.) se verity; defoliation rate; winter injury; cold hardiness of flower buds and shoot xylem; and tree survival. Rootstock effects on the above me asurements and ratings were significant in some years and not in other s. Year effects were always large and significant, while rootstock x y ear interactions were usually small and not significant. In the combin ed analyses over years, the largest rootstock effects were obtained fo r bloom, fruit set, and defoliation ratings and for TCA measurements. Three cumulative responses, including marketable yields, yield efficie ncy, and tree survival, were used for comparing the five experimental rootstocks with the five commercial standards and also for ranking the 10 rootstocks with respect to each other to assess their potential co mmercial value as peach rootstocks. 'Chui Lum Tao', H7338013, and 'Bai ley' had the most commercial potential for southern Ontario because th ey typically promoted above average cumulative yield, yield efficiency , and tree survival. 'Tzim Pee Tao','Siberian C', and 'Harrow Blood' w ere less valuable, with low cumulative marketable yields. 'Halford' an d 'Lovell' were the least valuable, with the lowest tree survival (17% ). Performance of H7338013 exceeded that of both parents (Bailey' and 'Siberian C'), H7338019 exceeded 'Siberian C' but not 'Bailey', while performance of H7338016 was inferior to both parents. Wider testing of the experimental rootstocks on different soil types and climatic zone s is needed.