[Breeding for digenic apple resistance to scab].
The results of the apple breeding for digenic resistance to scab (1979-2000), which is more long-term than the monogenic breeding, have been reviewed. The hybrid seeds obtained from the reciprocal crossing between the Vf and Vm resistance gene donors served as the original material. The seed progeny yielded by backcrosses between these hybrids and the susceptible cultivars were examined (age--first true leaves) using inoculation in a greenhouse. The following criteria were proposed for breeding parental forms and the cultivars of the VfvfVmvm genotype: (1) phenotype segregation in the progeny of three resistant: one susceptible seedling and (2) the presence in the progeny of two types of resistant seedlings: those with the class 1 resistance (points and spots-hypersensitivity) typical of the Vm gene and those with the class 2-3 resistance (chlorotic and necrotic spots) typical of the Vf gene.
Zhdanov
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VV
All-Russian Research Institute of Horticultural Breeding, Orel, 302530 Russia. vniispk@valley.ru
Sedov
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EN
D001947:Breeding; D002678:Chimera; D020022:Genetic Predisposition to Disease; D027845:Malus / Q000235:genetics*; D010935:Plant Diseases / Q000235:genetics*