Broadening the Genetic Base and Introgression of MYMV Resistance and Yield Improvement through Unexplored Genes from Wild Relatives in Mungbean

Abstract

Introgression of unexplored genes from the wild relatives could be rewarding for broadening the genetic base of important traits such as yield, yield attributes and resistance to biotic and abiotic stresses in pulses. Aimed at developing superior segregants for yield coupled with yellow mosaic virus resistance (MYMV), interspecific direct crosses were attempted in Vigna radiata var. VRM (Gg) 1 with two accessions of Vigna umbellata ( yellow and red). Even though crossability barriers were predominant, it was possible to recover interspecific hybrids in direct crosses. F 1 plants of V . radiata x V. umbellata were found to be intermediate in phenotype with light green colour leaves. The reproductive parts tend to resemble V. umbellate , with double peduncle in one leaf axis. No pod set was observed when F 1s were selfed nor in their corresponding backcrosses with the parents. The F 1 plants produced more than 4000 flowers per plant, but spontaneous sterility was observed both in female and male parts of the flowers. Detailed cytological studies were carried out for male and female sterility. Male sterility was due to meiotic irregularities viz., unequal separation of tetrads and female sterility was due to degeneration of megaspore during megasporogenesis. Hence, irradiation techniques were applied to recover fertile plants in F 1 hybrids. The parental seeds were irradiated with 100, 200, 300, 400 and 500 Gy doses. The pod set percentage was increased due to irradiation. In normal crosses, pod set ranged from 2.00% (VBN (Gg) 2 × Vigna umbellata red) to 4.40% (VRM (Gg) 1 × V. umbellata red). In crosses resulted from irradiated parents, pod set ranged from 2.70% (CO 6 × V. umbellata yellow) to 4.90% (VRM (Gg) 1 × Vigna umbellata yellow) among crosses involving parents treated with 100Gy. Fertile F 1 hybrid plants were obtained from a cross between Vigna radiata var. VRM (Gg) 1 and V. umbellata red ( both parents treated with 200 Gy). The fertile F 1 phenotype was generally towards the female parent, but traits like orientation of top leaves, tendrilness and number of seeds per pod shifted towards the male parent.