Volume 51 Number 4 Article 45
Year 1997 Month 10
Title: Field Susceptibility of Scab-Resistant Apple Cultivars and Selections to Cedar Apple Rust, Quince Rust and Frogeye Leaf Spot
Author: J. Warner
Abstract:
Thirty-seven scab-resistant apple cultivars and selections were evaluated in the field for level of susceptibility to cedar apple rust (CAR), Gymnosporangium juniperi-virginianae Schw., quince rust (QR), G
clavipes Cke. and Pk., and frogeye leaf spot (FLS), Botryosphaeria obtusa (Schw.) Shoemaker.
Between
1994 and 1996, fruit infection from CAR varied from 0 to 40% for the various cultivars and selections.
The
selections originating from the Geneva, N.Y. breeding program were resistant to CAR or had low levels of
fruit infection (0-3%). They also had low leaf rust ratings (0 to 0.3) except for NY 74828-12 which had leaf
rust ratings of 0.2 to 1.3 (1-25 lesions per leaf) over the three years.
The Quebec apple selections (QAS) from
Agriculture and Agri-Food Canada, St.
Jean, Quebec also had low levels of fruit infection from CAR (0 to
3%). However, several selections did have leaf rust lesions.
Other cultivars and selections with field resistance to CAR included 'Moira,' 'Novamac,' 'Redfree,' 'William's Pride,' Co-op 26, 0-637 and 547-25-52.
QR infection varied from 0 to 31% with 'Moira,' CBR4T29, Co-op 24, QAS-04, QAS-11 and 0-661 being
most susceptible with fruit infection of 10% or higher.
FLS occurred on all cultivars.
Those with 5 or fewer
lesions per leaf over the three years included 'Dayton,' 'Jonafree,' 'Novaspy,' CBR4T29, Co-op 12, Co-op
15, Co-op 19, Co-op 20, Co-op 24, QAS-01, QAS-03, NY 75414-1 and 0-661. In this trial, QAS-01 and NY
75414-1 had combined resistance to all three diseases.
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