Introgression of anthracnose resistance gene(s) into common bean (Phaseolus vulgaris)

Abstract. Kazimoto GK, Nchimbi-Msolla SF, Mabagala RB. 2022. Introgression of anthracnose resistance gene(s) into common bean (Phaseolus vulgaris). Cell Biol Dev 6: 20-31. Common bean anthracnose disease caused by the fungus Colletotrichum lindemuthianum causes significant yield losses. It is most destructive in areas with cool temperatures and high humidity (90-100%). The study aimed to introduce resistance genes into adapted but susceptible local cultivars of Masai Red and Soya Njano using conventional breeding methods. Five races of C. lindemuthianum were isolated and named from thirty-two common bean-diseased plant samples collected from Northern Tanzania. The sources of resistant genes were bean cultivars G2333 and AB136. Early developed populations were evaluated under field conditions in high altitude and humid environments at Bashnet in the Manyara region, in the Northern highlands of Tanzania. Both F2 and F3 populations of Soya Njano x G2333 were segregated for C. lindemuthianum resistance at a 9:7 ratio. Such segregation implied that two dominant epistatic genes conferred from G2333, the resistance being in the mode of epistatic gene interaction. The crosses between Masai Red x G2333 and F2 and F3 populations segregation ratio was 10:6, implying two dominant resistant genes were transferred to developed populations. The F2 and F3 progenies obtained from crossing Soya Njano and AB136 showed a ratio of 3:1. The F2 progenies from a cross between Masai Red and AB136 were segregated at a ratio of 3:1 and F3 progenies were 3:1. The 3:1 ratio confirmed single dominant gene inheritance conferred to developed progenies. The heritability (h²) from populations of Soya Njano x G2333 and Masai Red x G2333 was between 0.41 and 0.45. While Soya Njano, Masai Red, and A136 were between 0.2 and 0.53, which implied moderate heritability. F2 and F3 populations developed need further testing using MAS to confirm the presence of resistant genes. Multi-location testing should be done to verify the resistance levels of the developed bean population in later generations.