Diapause in Chilo partellus: A Research Journey

Abstract

Spotted stem borer, Chilo partellus (Swinhoe) is one of the most widely distributed pests of coarse cereals, causing 18 to 25% yield losses in Asia and Africa. The larvae of C. partellus pass through hibernation under North Indian and aestivation under South Indian conditions. Although diapause helps C. partellus in adapting under unfavorable conditions, there is 17.2 to 28.3% and 7.0 to 33.7% population sacrifice during hibernation and aestivation, respectively. The population heterogeneity in C. partellus could be due to hibernation or aestivation, wherein the models, Ikemoto & Takai (linear), and Lactin-1 and Lactin-2 (non-linear) are efficient for describing temperature dependent development and estimating the temperature thresholds of diapausing larvae. This helps in predicting the occurrence, seasonal emergence, number of generations and population dynamics of the pest. Diapause results in differential regulation of hormonal and biochemical profiles, impose deleterious effects on the post-diapause development, reproductive physiology and population growth of C. partellus. The diapause, developmental and morphometric traits in C. partellus are governed by overdominance gene effects which mainly depend on parental diapause history. Four different biotypes of C. partellus viz., Hisar, Hyderabad, Parbhani and Coimbatore exist in India, suggesting that sorghum and maize genotypes need to be tested against these four populations to identify stable sources of resistance. The whole genome sequencing will be useful for understanding mode of action of different insecticides, mechanisms of detoxification and designing target-specific insecticides to develop appropriate strategies to manage C. partellus for sustainable crop production. The temporal distribution of mating systems among adults of diapause, non-diapause and/or ecologically diverse populations, and their behavioral and physiological consequences under a given demographic framework could be rewarding, and aid in to devising appropriate mating disruption techniques to suppress C. partellus population.