Quantification of dilatory resistance in four rice cultivars to rice blast

Abstract

Dilatory resistance of two rice Cultivars, Jackson and Maybelle, to rice blast was expressed as decreases in different components of resistance. Incubation period was found to be more important in determining dilatory resistance than the other components of resistance. Lesion size and sporulation capacity were negatively correlated suggesting that increased lesion size is not necessarily indicative of decreased resistance. The negative correlation between infection frequency and lesion size further supports this idea. As sporulation capacity and infection frequency increased, incubation period decreased. These relationships imply that sporulation capacity may be more important in determining dilatory resistance than the data here suggest. P.grisea races IC-17 and IB-49 are commonly found in Texas. Component analysis found Maybelle to be more resistant to race IC-17 and Jackson to be more resistant to race IB-49 . The ability of these cultivars to withstand disease pressure in the field may therefore be influenced more by specific interactions between cultivar and pathogen population than by levels of dilatory resistance possessed by either Maybelle or Jackson.