Peroxidase activity; a potential criterion in breeding for field resistance toPhytophthora infestans

Summary The results of other experiments (cited in the references) showed that peroxidase activity (PA) in clones (cultivars or hybrids) was correlated with field resistance to late blight in uninoculated plants. In contrast, in our experiments where PA was tested in seedlings before inoculation and 5 and 15 days after it, the correlation was found only with PA data recorded after infection. Negative and positive correlations with PA were found, respectively, when the population structure was expressed in four size classes (before inoculation) or of attack intensity (after inoculation).