Morphological and chemical parameters associated with resistance to Callosobruchus chinensis in pigeonpea

The performance of 16 pigeonpea varieties/genotypes to Callosobruchus chinensis Linn. was assessed under laboratory conditions based on the development of the insect, seed damage and the various morphological/chemical parameters of the test varieties. Significant variation was observed among the varieties with respect to pest development and seed damage. The varieties PRG-158 and PRG-100, which recorded 0.0 and 0.8 index of susceptibility were categorized as resistant while seven varieties viz., Lakshmi, ICPL-87119, LRG-38, ICPL-8863, LRG-41, WRG-79 and WRG-65 exhibited moderate resistance (2.9 to 5.0) and the remaining 7 varieties/genotypes viz., MRG-66, LRG-30, WRG-27, WRG-53, WRGE-18, WRGE-14 and Durga showed moderate susceptibility (5.1 to 6.0 index of susceptibility) to bruchid infestation. Among the physical parameters, seed colour played a significant role on fecundity of the test insect while inter granular space showed significant influence on fecundity, developmental period, adult emergence and seed infestation. The chemical parameters like high ash and potash contents of test varieties were detrimental to the growth and development of test insect while protein content of the test varieties favoured the successful development of bruchids and high infestation.