Regulation of Insect Hormones in Different Types of Diapause in Chilo Partellus (Swinhoe).

Abstract

Maize stem borer, Chilo partellus (Swinhoe) is a key pest of maize and sorghum. It undergoes both in estivation and hibernation depending on prevailing environmental conditions. Present investigations were aimed to decipher the regulation of ecdysone, 20-hydroxyecdysone (20E) and juvenile hormone III (JH III) during different stages (prediapause, diapause and post-diapause/pupae) of hibernation and estivation as compared to counterpart nondiapause C. partellus. Significant variations were found in the ecdysone, 20E and JH III titers in the hemolymph of different stages of hibernation and estivation over the nondiapause C. partellus. At the prediapause stages of hibernation and estivation, the 20E was greater than the ecdysone. However, the ecdysone and 20E downregulated, while JH III upregulated during prediapause stages of hibernation and estivation as compared to nondiapause larvae. During diapause, 20E decreased in hibernation, and increased in estivation as compared to their respective prediapause stages. The JH III significantly upregulated in diapause stages of hibernation and estivation over the nondiapause larvae. However, it was significantly greater in prediapause and diapause stages of estivation as compared to hibernation strain. During post-diapause stage, the ecdysone and 20E titers were greater in estivation than in the hibernation and nondiapause strains, while JH III was greater in nondiapause than in the hibernation and estivation strains. These findings suggest the crucial role of these hormones in establishing switch between different stages of diapause and metamorphosis in C. partellus, which could further be useful to strategize sustainable management of C. partellus.