Effect of two protein elicitors extracted from Alternaria tenuissima and Beauveria bassiana against rice leaf folder (Marasmia exigua)

Abstract

The rice leaf folder, Marasmia exigua (Butler), is dangerous pests and negatively affecting the rice production worldwide. Protein elicitors are considered to be bio-factors that induce rice resistance against herbivores. The present study was performed with two protein elicitors, Hrip 1 (extracted from Alternaria tenuissima) and PebB1 (from Beauveria bassiana) to study their efficacy against the rice leaf folder. Three different concentrations of Hrip 1 (68.88, 46.69 and 28.44 µg/ml) and PebB1 (56.66, 39.76 and 32.62 µg/ml) were assigned to evaluate the developmental time, survival rate, and fecundity of M. exigua. Both elicitors were applied to the three-leaf stage of the rice plant where newly emerged adult insects were released. Bioassay results showed that after the application of protein elicitors, the life cycle and survival rate of the rice leaf folder were prolonged, while fecundity decreased. The concentration of protein had a significant (p < 0.05) influence on ontogeny. In addition to ontogeny, the expression profile of jasmonic acid, salicylic acid, and ethylene associated with signalling pathway, which indicated that exogenous application of both elicitors produced a significant up-regulation in all the genes associated in signalling pathways of the plant. The plants treated with elicitors produced resistance against M. exigua (as compared to the control). This in vitro study invites new research into Hrip 1 and PebB1 as having prophylactic potential against rice leaf folder, and suggest that both protein elicitors can be used as a novel biological control tool for M. exigua.