Components of partial resistance to Stagonospora blotch among Brazilian spring wheats

Abstract

Thirty-two Brazilian spring wheats (Triticum aestivum L. em. Thell.) were evaluated for partial resistance to Stagonospora blotch under greenhouse conditions to an isolate of Stagonospora nodorum from the southeastern U.S. Incubation period was shortest (5.6 days) in the susceptible cultivar BR 4 and longest (12.7 days) in the resistant cultivar CEP 14. Latent period was significantly longer for CEP 14 than on any other cultivar except BR 38. Resistant wheats had latent periods that were 3–5 days longer than susceptible lines. Disease severity was negatively correlated (P < 0.01) with incubation period and latent period. Cultivars with long incubation period and long latent period also had a slow rate of disease progress. The widest range of response to S. nodorum infection was for area under the disease progress curve (AUDPC). CEP 14 and BR32 had AUDPC values that were less than 25% of the values of seven cultivars with the highest AUDPC. CEP14 had the longest IP and LP and the lowest AUDPC, exceeding the next closest entry by almost 5% for each parameter. Ratings for components of partial resistance closely paralleled field ratings for resistance in southern Brazil. Because genotypes are generally well-adapted agronomically and responded similarly to an isolate representative of S. nodorum in the southeastern U.S., resistant lines from southern Brazil may be useful in breeding programs in the southern U.S.