Biophysical and biochemical mechanism of resistance to Spodoptera litura in groundnut (Arachis hypogaea L.)

Abstract

Spodoptera litura (S. litura) is an important insect pest affecting the yields of groundnut worldwide and host plant resistance is a key pest management strategy. Understanding the mechanism of resistance to S. litura would help in developing resistant cultivars. In the present study, biophysical (trichome density, relative water content, specific leaf weight, epicuticular wax) and biochemical (reducing, non-reducing and total sugars, protein and phenol content) parameters were analysed in the eight selected S litura resistant groundnut genotypes and four checks along with a wild species Arachis monticola L. Significant negative correlation was observed between S. litura damage and specific leaf weight, midrib, leaf lamina trichome density, wax content, protein and phenol content while, significant positive correlation with reducing and total sugar. Among the S. litura resistant genotypes, ICG 928 had higher leaf lamina (140 mm-2) and midrib (180 mm-2) trichome density, specific leaf weight (2.5 g/dm2), wax content (0.36 µg/cm2), protein (4.91 mg/g), and phenol content (3.77 mg/g) compared to susceptible check JL 24 which had higher relative water content (73.3 %), reducing sugar (11.32 mg/g), total sugar (12.75 mg/g) and lower leaf lamina (60 mm-2) and midrib trichome(30 mm-2) density, specific leaf weight (2.2 g/dm2), wax content (0.2 µg/cm2), protein (2.39 mg/g), and phenol content (2.03 mg/g). These biophysical and biochemical components can be effectively utilized in breeding for resistance against S. litura in groundnut.