Stress driven divergence: Biochemical and enzymatic insights into aphid morph diversity

Ecological forces shaping aphids diversity

Abstract

Indian mustard (Brassica juncea (L.) Czern. & Coss.) is a vital oilseed crop in India, yet its productivity is severely impacted by the mustard aphid (Lipaphis erysimi Kaltenbach), a major pest causing substantial yield losses up to 10-90 %. Understanding the population dynamics and physiological adaptations of apterous and alate morphs of mustard aphid under field conditions is vital for developing effective pest management strategies. This study aimed to investigate the seasonal incidence, biochemical composition, and enzymatic responses of winged (alate) and wingless (apterous) morphs of L. erysimi to abiotic stress. Field monitoring from December 2023 revealed a negative correlation between aphid incidence and maximum temperature (r = -0.682**) and a positive correlation with predator populations such as ladybird beetles (r = 0.923*) and spiders (r = 0.586^*). Biochemical analyses indicated differential resource allocation, with apterous aphids accumulating more glucose and protein, while alates exhibited higher triglyceride levels. Spectrophotometric assays showed elevated antioxidant enzyme activity (Superoxide Dismutase and Catalase) in alates, reflecting enhanced oxidative stress defences during dispersal. Lipid peroxidation was significantly higher in alates, underscoring the physiological cost of flight. These findings highlight the role of abiotic factors and natural enemies in shaping aphid populations and provide insights into stress adaptations, crucial for designing ecologically sustainable pest control strategies.