Inheritance of resistance to Mungbean Yellow Mosaic Virus (MYMV) in mungbean [Vigna radiata L. Wilczek]

Six basic populations (P₁, ^P2^{, F}1, ^F2, ^B1and B₂) of 12 crosses involving two resistant and six susceptible mungbean genotypes were screened to study the inheritance pattern of MYMV resistance. All the 12 F₁s were susceptible indicating that the susceptibility is dominant over resistance. The F₂^’s of each of the 12 crosses exhibited a segregation ratio of 9S: 3MS: 3MR: 1R indicating the involvement of two recessive genes (r₁ and r₂) in the inheritance of MYMV resistance. When both genes were present together in a homozygous dominant state, R_1-^R2, plants were highly susceptible (S). In contrast, when both the genes were in homozygous recessive condition, r₁^r1, ^r2^r2, the resistant reaction was obvious. However, when one gene was in homozygous recessive (R₁, r₂r₂) condition, moderate susceptibility (MS) was observed while, when the other gene was in homozygous recessive (r₁^r1, ^R2) condition, moderate resistant (MR) reaction was observed. Thus, the F₂ segregation, 9 (R₁R₂): 3 (R₁r₂r₂): 3 (r₁r₁R₂): 1 (r₁r₁r₂r₂), was explained on the basis of phenotypic expression, 9S: 3MS: 3MR: 1R, which was further confirmed in a back cross generation.