REACTION OF VARIOUS BARLEY GENOTYPES ON INFECTION, FREQUENCY AND GENES COMPLEXICITY OF ERYSIPHE-GRAMINIS DC F-SP HORDEI MARCHAL IN SLOVAKIA

In 1995, the disease severity, frequency and complexity of virulence g enes of Erysiphe graminis DC. f. sp. hordei Marchal on 10 spring barle y cultivars with different resistance genes were studied. Under field conditions, only the cv. 'Forum' with resistance gene ml-o was without sporulation of the pathogen. The most significant attack was determin ed in cv. 'Rubin' with the resistance gene Ml-a(1). On the base of vir ulence analysis, significant differences between isolates originating from different genotypes were determined. In the population of pathoge ns isolated from examined genotypes, the highest virulence genes frequ ency was determined against resistance genes of individual cultivars. According to the complexity of virulence genes, the lowest mean number of virulence in analyzed isolates was found from the genotype with re sistance gene Ml-a(12) and the highest one from genotypes with resista nce genes Ml-a(6) + at and Ml-a(9) + La.