Seed trait influence on Callosobruchus maculatus behaviour and performance in legume hosts

Pulses are essential components of agricultural production systems, post-harvest losses caused by storage insect pests remain a major challenge. Callosobruchus maculatus (F.) is a widespread pest of stored legumes, and its host preference is influenced by seed type and associated physico-biochemical traits. This study examined the determinants of C. maculatus preference among nine legume species using controlled laboratory assays and seed trait analyses. Under no-choice conditions, chickpea ( Cicer arietinum L), pigeon pea ( Cajanus cajan L.) , and moth bean ( Vigna aconitifolia (Jacq.) Maréchal) supported high oviposition, larval development, and adult emergence, suggesting their overall biological suitability as hosts. In contrast, the common bean ( Phaseolus vulgaris L.) was the most preferred oviposition substrate under free-choice conditions but exhibited poor hatching and emergence, indicating its role as an oviposition trap. Black gram ( Vigna mungo L.) , soybean ( Glycine max (L.) Merr) , and moth bean, though less preferred, supported high post-embryonic success, revealing latent susceptibility. Green gram ( Vigna radiata L. ), black gram, red gram, cowpea ( Vigna unguiculata L. ), and moth bean exhibited high intrinsic suitability, reflected by positive growth indices, shorter developmental durations (notably in black gram and green gram), and balanced oviposition with adult longevity. Principal component analysis identified two major axes of host discrimination: (i) physical traits governing oviposition preference and (ii) biochemical composition determining larval development. Seeds with greater surface area, thinner seed coats, and moderate sphericity were favoured for egg deposition, whereas high protein and carbohydrate content enhanced larval growth. In contrast, anti-nutritional factors such as tannins and phytic acid negatively affected larval performance. These findings underscore the significance of integrating physico-biochemical resistance traits into legume breeding and storage management strategies to reduce bruchid-related post-harvest losses.