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Fruit Varieties Journal
(Fruit Var J)

American Pomological Society

Volume 48 Number 1 Article 7 Pages: 34-34
Year 1994 Month 1
Title: An Explanation for Reports of Apple Scab Infection on Fruit of NY 74828-12
Authors: S.K. Brown and L. Berkett
The occurrence of scab in Vermont on one fruit from the scab resistant advanced selection NY 74828-12 was noted at harvest in 1992. In 1993 both fruit and foliar symptoms have been observed on this selection in Pennsyl vania with scab-like symptoms on the foliage in Vermont. While these re- ports have raised concerns about the reakdown of the Vf gene for resistance to apple scab, there have been no reports of any infection of advanced selections or cultivars with the Vf gene for resistance. Although there are sev eral genetic sources of resistance to scab, Vf is the predominant source used by most breeding programs. Exam ination of the breeding record of NY 74828-12 reveals that its source of resis tance to scab is M. atrosanguinea 804. This source of resistance can confer either the Vf gene or the Vm for resis tance. NY 74828-12 has the V gene for resistance as evidenced by the occurrence of transient pit type lesions from controlled inoculations of scab. The Vm gene is susceptible to race 5 of apple scab, unlike Vf, which is resistant to race 5. The development of scab in Vermont, and the report of scab symp toms on NY 74828-12 in the Rodale Institute Research Center orchards in Pennsylvania this year indicates that race 5 exists within these areas. The infection observed on NY 74828-12 will help us to assess the prevalence of race 5 within our growing regions and to gauge the rate and extent of disease development. Researchers and growers testing NY 74828-12 are encouraged to contact the authors if scab infections are noted in their test plots.

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