Development of a new powdery mildew and Cercospora leaf spot-resistant mungbean cultivar using marker-assisted backcross breeding

Chai Nat 84–1 (CN84-1) is one of the most popular Thai-certified mungbean cultivars widely grown in Thailand, known for its large seeds and high yield. However, this cultivar is susceptible to powdery mildew (PM) and Cercospora leaf spot (CLS). These are the major foliar diseases in mungbean production that can significantly reduce both the quality and quantity of yields. In the present study, the pyramiding of 2 PM and 1 CLS resistance genes from donor parents A and B into elite variety CN84-1 was achieved through marker-assisted backcross breeding (MABB). The progenies pyramided with the three resistance genes in each cross from the BC 1 F 1 to BC 4 F 1 generations were identified using six markers linked to these resistance genes. A high percentage of recurrent parent genome (RPG) recovery, with a maximum of 97.6% and 100.0% in BC 4 F 1 generation, was obtained through background selection. Under field conditions, Most BC lines resisted PM and CLS better than CN84-1, especially P12. Additionally, most BC lines exhibit agronomic traits and yield performance similar to or superior to CN84-1. In particular, P08, P12, P22, and P24 exhibited strong overall performance and achieved yields ranging from approximately 7% to 32% higher than CN84-1. Our findings indicate that MABB is an efficient approach to pyramid multiple resistance genes and accelerate backcrossing in mungbean. Moreover, these BC lines could be developed into new mungbean cultivars with resistance to PM and CLS, as well as good yield performance in the future.