Pyramiding of powdery mildew and leaf spot resistance genes in mungbean using marker-assisted backcrossing

Mungbean or green gram (Vigna radiata (L.) Wilczek) is one of the important economic crops in Thailand. Protein and several important nutrient sources for human consumption were found in mungbean seeds. However, the current mungbean production is not enough for its requirement due to poor harvest index, lack of genetic variability, susceptibility to abiotic stresses and particularly biotic stresses. Cercospora Leaf Spot (CLS) and powdery mildew (PM) are the major foliar diseases in mungbean production that can reduce the quality and quantity of mungbean yields. CN84-1 with high yield and starch percentage is widely grown in Thailand, but highly susceptible to CLS and PM diseases. In the present study, the pyramiding of 1 CLS and 2 PM resistance genes from donor parents A and B into elite variety CN84-1 was achieved through marker-assisted backcross breeding (MABB). The triple pyramided progenies in each cross from BC₁F₁ to BC₄F₁ generations were identified using 6 linked markers to these resistance genes. Using background selection, high percentage of recurrent parent genome (RPG) recovery with a maximum of 97.6 and 100.0% in BC₄F₁ generation was obtained through 24 and 26 polymorphic ISSR loci of cross A and B, respectively. These results indicate that the pyramided progenies in the advanced generation contain a similar genome with CN84-1 and three resistant genes. Our findings indicate that MABB is an efficient approach to pyramid multiple resistance genes and accelerate backcrossing in mungbean.