Genetics and Breeding for Bruchid Resistance in Asiatic Vigna Species

Abstract

A bruchid [Callosobruchus chinensis (L)] is the most common destructive pest of stored grain legumes such as mungbean [V. glabrescens (L)], black gram [V. mungo (L)], rice bean [V. umbellata (L)], and adzuki bean [V. angularis (L)]. The initial infestation starts in the field at pod maturity; a secondary infestation under poor storage conditions destroys the seeds within 3 to 4 months. The use of insecticides or fumigants is not practical in bruchid control since the seeds are used for human consumption. Therefore, developing bruchid resistant cultivars could be an effective way to minimize the losses due to bruchid attack. Many sources of resistance to bruchid infestation have been reported in black gram, VM2011 and VM2164 (AVRDC); ‘Sindh Khed’(India) and in mungbean, V 2802 (AVRDC); EG-Glabrous, EG-MG4, EG-MG7 (Philippines) and in wild Vigna species, V. glabrescens and V. mungo sub. sp. silvestris (AVRDC). Blackgram accession VM2011 was least damaged when the bruchid infestation occurred in the field, while in laboratory screening, VM2164 was highly resistant. Dense pubescence in VM2011 and hard seed coat or possible antibiosis in VM2164 were probably the causes of the resistance. The physical characteristics (seed size, seed coat thickness, seed color) appeared to be related to genotypic susceptibility. The inheritance of bruchid resistance is controlled by the genotype of the maternal parent and appeared to be controlled by recessive genes which complicates the selection and breeding for bruchid resistance. With these constraints in mind, a breeding method is proposed to introduce bruchid resistance from multiple genetic sources to improved mungbean cultivars.