Differential Aggressiveness in a Uruguayan Population of Cochliobolus sativus on Barley

Abstract

Spot blotch induced by Cochliobolus sativus is one of the most important foliar diseases of barley (Hordeum vulgare L.) due to yield and quality reduction. The use of cultivars with genetic resistance is the basis of an integrated disease management; however, its effectiveness may be affected by the type and level of genetic resistance and by variations in aggressiveness in the pathogen population. In this study, the aggressiveness diversity of forty-four monosporic isolates of. C. sativus was evaluated on twenty-eight barley genotypes under conditions of controlled temperature and photoperiod. Eight isolates only induced infection responses indicative of high host-parasite compatibility, but they were different from each other considering the other two infection response types. The highest frequency of responses (84%) – indicative of low compatibility host-parasite interaction – was found in only two isolates. Resistance levels varied from 63. 6 % to 0% with an important range of different performances for this group of isolates. The high intrinsic variability of the interaction was remarkable. Studies with more diverse pathogen and barley samples will allow a deeper understanding of the dynamics of this host-parasite relationship and would be useful to develop focused breeding strategies, aimed to obtain cultivars with more effective and durable resistance.