Identification Of Colletotrichum Lindemuthianum And Introgression Of Its Resistance Gene(S) To Common Bean (Phaseolus Vulgaris L.) Adapted In Tanzania

ABSTRACT

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 aim of the study was to introgress resistance gene into adapted but susceptible local cultivars Masai Red and Soya Njano using conventional breeding methods. Five races of C. lindemuthianum were isolated and named, from thirty two common bean diseased plants samples collected from Northern Tanzania and Nyadira, in Morogoro region. The races names varied with locations in which they were collected. The sources of resistant genes were bean cultivars G2333 and AB136. Early populations developed were evaluated under field conditions in high altitude and humid environment at Bashnet in Manyara region, in the Northern highlands of Tanzania. Both F2 and F3 populations of Soya Njano x G2333 segregated for C. lindemuthianum resistance at 9 : 7 ratio. Such segregation implied that two dominant epistatic genes conferred from G2333, the resistance being in mode of epistatic gene interaction. The crosses between Masai Red x G2333, both F2 and F3 populations segregation ratio was 10 : 6 which implied two dominant resistant genes were transferred to developed populations. The F2 and F3 progenies obtained from crossing Soya Njano and AB136 showed a segregation ratio of 3:1. The F2 progenies from crosses between Masai Red with AB136, segregated at a ratio of 3: 1 and also F3 progenies was 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 was between 0.2 and 0.53, which implied moderate heritability. F2 and F3 populations developed need further testing using MAS to confirm presence of resistant genes. Multi location testing should be done for verification of resistance levels of developed bean populations in later generations.