Field evaluation of cauliflower genotypes against alternaria blight and role of phenols and oxidative enzymes in fungal resistance

Sixty cauliflower genotypes comprised of 10 early season, 20 main season and 30 late season were screened against Alternaria blight under field conditions and evaluated for phenols and oxidizing enzymes in relation to resistance/susceptibility to alternaria blight at seedling and curd initiation stage. On the basis of per cent disease index (PDI), sixty genotypes were categorized into moderately resistant (8), moderately susceptible (44), susceptible (7) and highly susceptible (1). None of the genotypes was found to be immune or resistant to disease. Moderately resistant genotypes recorded higher levels of total phenols and activity of phenylalanine ammonia lyase, peroxidase, polyphenol oxidase and superoxide dismutase at both the stages than the susceptible ones. The total phenols and the oxidative enzymes were negatively correlated with PDI, but the most significant correlation was found between per cent disease index and total phenols suggesting a significant role of phenols in resistance against Alternaria blight in cauliflower genotypes.