Grain Morphological Traits Confer Tolerance to Bruchid (Callosobruchus maculatus) Infestation of Stored Green Gram (Vigna radiata L. Wilczek)

Abstract

Post-harvest losses due to bruchid (Callosobruchus maculatus) infestation in green gram production remain a challenge. The relative tolerance to bruchid infestation of five green gram (Vigna radiata L. Wilczek) varieties was evaluated under ambient conditions in a laboratory. The green gram varieties were two old varieties: N26 and KS20; and three new varieties: Karembo, Biashara and Ndengu-Tosha. A completely randomized design with four replications was used in the laboratory. Callosobruchus maculatus was isolated from infested green gram grain and multiplied on clean grain for artificial infestation. Data collected include seed coat color, seed size, seed weight loss, seed coat thickness, number of holes on grain and oviposition. Analysis of variance at P = 0.05 using GenStat 15th Edition statistical software was done and treatment means separated using the Fisher’s Protected Least Significant Difference at 5% probability level. Data were further subjected to simple linear regression analysis to determine relationships among variables. Seed morphological traits mainly thick seed coat and small seed size were associated with reduced oviposition on the grain. Correlation analysis revealed a positive relationship between seed color and egged grain (0.40 ≤ R2 ≤ 0.63). Ndengu Tosha and Karembo varieties with higher hue angles (100 ± 8.1 Ho) supported fewer dead bruchids (1 and 15 respectively), suggesting reduced suitability for oviposital preference. The findings highlight the potential of varietal selection as a sustainable strategy for minimizing postharvest losses, reduced pesticide reliance in green gram and increased income of small scale farmers. Future research should focus on developing new varieties with grain traits that are tolerant to bruchid attack.