Infection by rice blast makes rice more attractive to fall armyworm

Plants face numerous hardships from stressors, and herbivore feeding can change plant physiology at a systemic scale triggering a cascade of interactions that function to protect the plant from subsequent herbivores-or pathogens.  These responses are manifested by changes in gene expression related to primary and secondary metabolism in the plant. Rice, Oryza sativa L, is an interesting model for the study of herbivore-pathogen interactions. Despite the economic importance of rice, pathogen- and herbivore- induced responses have received little attention. The fall armyworm, Spodoptera frugiperda, is considered a sporadic, but destructive pest of rice in Louisiana. Rice blast, caused by the fungus Magnaporthe oryzae, is one of the most devastating diseases of rice. We hypothesize that the interactions of rice plants with rice blast make plants more susceptible to S. frugiperda. Greenhouse experiments to characterize rice resistance to S. frugiperda were conducted after inoculation with rice blast. Weight gains and relative growth rates of FAW larvae were higher when fed leaves from plants previously infected by rice blast than when fed leaves from undamaged plants. These results show that rice blast may have a significant impact on resistance to subsequent insect attack suggesting that defense/susceptibility regulatory genes may be involved.