ANALYSES OF INTERACTIONS OF WHEAT CULTIVARS IN TESTS FOR RESISTANCE TO PSEUDOCERCOSPORELLA-HERPOTRICHOIDES

A total of 20 cultivars of winter wheat were tested by ELISA for resis tance to Pseudocercosporella herpotrichoides in six environments and t hree growth stages. In a three-factor statistical analysis, the contri bution of the different factors to their respective interactions was s tudied. The genotype x environment interactions exerted a considerable influence which could be reduced by increasing the number of test loc ations. Environments with a high disease level were less suited to mea suring resistance than those environments with a medium level. Estimat es of heritability from 0.54 to 0.78 show that successful selection ma y be possible using ELISA. Significant correlations of quantitative re sistance at different environments were only obtained under similar en vironmental conditions (the same location, the same year) and with P. herpotrichoides populations of similar composition (the same inoculum) . The contributions of the individual cultivars to the genotype x envi ronment interactions were not significantly different, except for 'Roa zon' and 'Rendezvous'. Due to high environmental effects in growth sta ge 85, the determination of quantitative resistance was more reliable in younger stages (65, 75). Nevertheless, the use of the values from t hat late stage did not reduce the genetic parameters (sigma(c)(2), h(2 )) if they were combined with the earlier measurements.