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
Citation
Abstract:
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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