Components of Resistance toPuccinia arachidisin Peanuts

Abstract

Thirty peanut genotypes were inoculated with uredospores of the rust fungus Puccinia arachidis in a replicated glasshouse trial, and components of disease resistance—incubation period, infection frequency, pustule diameter, percent ruptured pustules, and percent leaf area damaged—were studied for a single cycle of infection. All components studied were significantly correlated with one another and with mean field rust scores taken over several seasons. Incubation period was negatively correlated with the other components, which were positively correlated with one another. Resistant and susceptible genotypes were readily separated on the basis of the resistance components measured in the glasshouse trial, but classification of moderately resistant genotypes was less effective by this method than by use of field scores. A glasshouse screening method could be useful in areas where rust epidemics do not occur or are irregular in occurrence or where other foliar diseases interfere with field screening. The measurement of epidemiologically significant characters will allow the identification of rate-limiting resistance, which is likely to be more stable than immunity.