Morphological and biochemical traits associated with resistance to groundnut bruchid, Caryedon serratus (Olivier), in groundnut (Arachis hypogaea L.)

Groundnut ( Arachis hypogaea L.) is an important oilseed crop that suffers substantial post-harvest losses due to infestation by the groundnut bruchid, Caryedon serratus (Olivier). The present study evaluated twenty-four groundnut genotypes to identify morphological and biochemical traits associated with resistance to C. serratus . One hundred grams of pods of each genotype were placed separately in plastic jars and five pairs of freshly emerged adults were released into each jar. Genotypes were screened using a no-choice test based on oviposition, adult emergence, developmental period, growth index, susceptibility index, pod damage and weight loss. Significant variation was observed among genotypes for all biological parameters. Oviposition ranged from 23.0 to 101.0 eggs per 100 g of pods, while adult emergence varied from 17.33 to 82.33 adults per 100 g. The susceptibility index ranged from 5.67 to 10.14, with K-9 recording the lowest value and K-7 the highest. Weight loss and pod damage (by weight) ranged from 7.5 to 14.0% and 22.8-40.2%, respectively. K-9 and Lepakshi consistently exhibited lower oviposition, reduced adult emergence, lower susceptibility index and minimum storage losses, whereas K-7, Dharani and K-2327 were identified as the most susceptible genotypes. Pod shell thickness varied from 0.71 to 0.87 mm, and thicker pod shells were associated with reduced insect development. Total soluble sugars ranged from 3.36 to 5.84%, proteins from 18.92 to 24.64%, total phenols from 196.42 to 321.78 mg CAE 100 g −1 , and tannins from 13.80 to 16.84 mg TAE g −1 . Correlation analysis revealed a significant negative association of pod shell thickness (r = −0.736) and total phenol content (r = −0.683) with growth index, indicating their contribution to host tolerance. Principal component analysis further differentiated tolerant and susceptible genotypes based on combined morphological and biochemical traits. The study identified K-9 and Lepakshi as promising sources of resistance and demonstrated that pod shell thickness and phenolic content are reliable indicators for breeding groundnut cultivars with improved resistance to C. serratus and for developing sustainable post-harvest pest management strategies.