Occurrence of Venturia inaequalis races in Poland able to overcome specific apple scab resistance genes

Sylwester Masny

doi:10.1007/s10658-016-1003-x

Abstract

The aim of this study was to confirm the presence of races in populations of the fungus Venturia inaequalis that are able to overcome specific apple scab resistance gene(s) within the major apple-growing areas of Poland. The monitoring was conducted in six orchards located in the north, centre and south of Poland. The study involved the use of 16 differential genotypes for pathogenicity testing conducted under both greenhouse and orchard conditions. In addition, the occurrence of apple scab on 10 apple cultivars containing the Rvi6 gene was assessed in four organic orchards in central Poland. Apple scab was found on their leaves for the first time in Poland in 2010. The use of differential genotypes containing specific resistance genes suggested that 10 apple scab resistance genes had been overcome by V. inaequalis in the orchards monitored in this study.

Highlights

Apple scab (Venturia inaequalis [Cooke] Wint.) is one of the most serious diseases of apple trees in many apple-growing regions
Studies investigating the genetic background of resistance and the breeding of apple trees for resistance were first undertaken in the USA
Crandall, gathered a large collection of species and clones of wild apple trees and began an intensive study on crossbreeding them with cultivated apple cultivars (Crandall 1926). He observed that clone 821 of the wild species Malus floribunda was completely resistant to apple scab

Summary

Introduction

Apple scab (Venturia inaequalis [Cooke] Wint.) is one of the most serious diseases of apple trees in many apple-growing regions. Crandall, gathered a large collection of species and clones of wild apple trees and began an intensive study on crossbreeding them with cultivated apple cultivars (Crandall 1926). He observed that clone 821 of the wild species Malus floribunda was completely resistant to apple scab. This work led to the selection of the ‘Prima’ cultivar. This cultivar was the first bred by the PRI programme with a satisfactory fruit size and quality (Dayton and Mowry 1970). In the second half of the twentieth century, other countries had begun to breed for apple scab resistance (Kozlovskaya et al 2000, Sansavini et al 2002)

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