Abstract The paradigm shift in climatic patterns has completely transformed the pest dynamics in jute cultivation. The Bihar hairy caterpillar ( Spilosoma obliqua Walker), formerly deemed sporadic, has presently evolved as a key pest, exacting serious attention. This study aims to identify resistant sources among wild, indigenous, and cultivated genotypes of dark jute. The interrelationship between the biochemical, anatomical, and molecular attributes of the host and larval consumption and growth parameters was studied to unveil the mechanisms underlying its defence response. The results suggested that the larvae exhibited varied food consumption and utilization, which was highly dependent on the host's nutritional and allelochemical attributes. Leaf protein content, trichome type, density, and lignin content influenced the larvae's consumption and growth rate, while allelochemicals like total phenol and antioxidative enzymes significantly deterred these indices. Efficiency of conversion of digested food and conversion of ingested food, as well as the consumption index of the larvae, were some of the most vital parameters that determined the host's resilience. Multivariate analysis classified the genotypes into three major clusters. Gene expression analysis revealed that the upregulation of defence‐related genes like peroxidase ( Co‐POD ), phenylalanine ammonia lyase ( Co‐PAL ), cinnamyl alcohol dehydrogenase ( Co‐CAD ), and dirigent proteins ( Co‐DIR ) played a critical role in jute defence against S. obliqua infestation, with significant variations between resistant and susceptible genotypes, while TRANSPARENT TESTA GLABRA1 ( Co‐TTGLA1 ) exhibited complex, genotype‐specific expression patterns. The highly resistant wild lines (WCIN179 and WCIN136) and resistant indigenous lines (OIN149 and OIN147) represent valuable genetic resources for jute breeding programmes for mitigating S. obliqua infestation.
Dash et al. (Wed,) studied this question.