Resistance to scab (Venturia inaequalis) and mildew (Podosphaera leucotricha) and fruiting properties of the offspring of the apple cultivar Antonovka

Abstract

SUMMARY Progenies obtained from crosses between selections from open-pollinated ‘Antonovka’ and other apple cultivars and from subsequent backcrosses, were observed for resistance to scab (Venturia imzequulis) and to mildew (Podosphaera leucotrichu) and fruiting characters. Scab resistance in the field greatly varied with the weather conditions. In the greenhouse or under favourable conditions for scab infection in the field, only a few percent of the seedlings of progenies of the second back-cross were found resistant. The ‘Antonovka’ progenitors also transmitted mildew resistance, which increased when ‘Lord Lambourne’ was used as a partner, but no immune seedlings occurred in the nursery. With age susceptibility decreased to the extent that a fair proportion of the seedlings were found to be resistant in the field in later years. The degree of scab resistance noted in trees in the orchard was closely relatad to that observed in the greenhouse; orchard and nursery observations significantly correlated for both scab and mildew. There was also a strong correlation between scab infection of the fruits and that of the leaves. Fruit properties of Antonovka offspring of the third generation were on average about the same as those of cultivar progenies. It is pointed out that breeding on the basis of multigenic resistance in large-fruited ‘Antonovka’ selections may not be less efficient than breeding on the basis of monogenic resistance in small-fruited Mulus species.