Vol. 69 No: 3

Title:
Field Resistance of Apple Rootstocks to Phytophthora Cactorum Infection

Authors:
R.S. UTKHEDE and E.M. SMITH

pp: 467-472

Abstract:
Six different two year old apple rootstocks with ‘Spur McIntosh’ scions were inoculated with Phytophthora cactorum and evaluated for susceptibility to this pathogen at the Summerland Research Station from 1982–92. In addition the effect of nursery source on the susceptibility of three rootstocks was compared. The rootstock MM.111 remained healthy for ten years while MM.106 was very susceptible to P. cactorum crown rot. No significant difference in resistance to P. cactorum was observed between MM.111 and M.4, and M.7a. Fruit yield was significantly lower for MM.106 than with MM.111, M.4, M.7a, and M.7 in 1990 and 1992. The susceptibility of M.26 from both nurseries to P. cactorum was similar to that of MM.106 from Traas Nursery. A significant difference in susceptibility to P. cactorum was observed between the two sources of MM.106 rootstock from 1984–1990; the MM.106 rootstock from Budwood Orchard was more susceptible to P. cactorum than that from Traas Nursery. However, in 1991 and 1992 (final observation) no significant difference was observed between them for susceptibility to P. cactorum infection. This study indicates that the observed variability in field resistance to P. cactorum crown rot infection should be explored for breeding for P. cactorum resistance.

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