QTL analysis for resistance to anthracnose in bukoba X kijivu population of common bean (phaseolus vulgaris).
Date
2024
Authors
Kachapulula, Josephine Ssali Namugerwa
Journal Title
Journal ISSN
Volume Title
Publisher
The University of Zambia
Abstract
The fungus Colletotrichum lindemuthianum which causes anthracnose disease in common bean (Phaseolus vulgaris L.) has a high genetic variability that requires deployment of loci with resistance to a wide range of C. lindemuthianum races. Most of the loci have been sourced from the Middle American genepool which are usually small seeded requiring many generations of back crossing to recover the original big seed size in Andean gene pool varieties which are also the required market classes in Zambia. This requires identification of loci with durable resistance from the Andean gene pool to reduce the time and cost of resistance breeding. Two Andean parents were used in this study Bukoba (ADP 7) and Kijivu (ADP 33). From previous studies by Sansala et al., (2023), the Andean variety Bukoba showed resistance to a number of races of C. lindemuthianum however the genetic architecture of this resistance was unknown and thus this study. A population of 158 F4:5 Recombinant Inbred Lines (RILs) were developed from a cross of two Andean parents Bukoba and Kijivu and evaluated at the University of Zambia, Lusaka, Zambia. The seven races for this study were 19, 38, 51, 167, 263, 1050 and 1105. These were selected based on their prevalence in Zambian bean growing regions and the virulence levels. The population was genotyped using 12000 SNPs out of which 1,838 were polymorphic between the parents and used to build genetic maps. Composite interval mapping was used to identify the quantitative trait loci (QTL). A total of 8 QTLs: ANT01.1, ANT01.2, ANT02.1, ANT04.1, ANT05.1, ANT06.1, ANT10.1 and ANT11.1 with R2 values ranging from 3.6% for ANT06.1 on Pv06 to 70.1% for ANT01.1 on Pv01 were identified. These were both novel and verified conditioning major and minor resistance to the seven races of C. lindemuthianum in this study. ANT01.1 and ANT04.1 were major QTLs while the rest were minor QTLs suggesting the role of both qualitative and quantitative resistance in the mapping population. The major QTLs identified in this study co-localized with previously reported major genes proving their usefulness as target genes for developing durable resistance to anthracnose using gene pyramiding and marker-assisted selection. ANT01.1 co localised with the Co-1 locus a major Andean locus that conditioned resistance to the very virulent races 1050 and 1105 in this study while ANT04.1 controlled four moderately virulent races 19, 51, 183 and 263. This locus co-localises with well-known Middle American loci Co 3, Co-15, Co-16, Co-y and Co-z and the NB-ARC domain cluster that are responsible for resistance to a number of the pathogen’s races. Although ANT02.1 was a minor QTL, but due to its co-localisation with the I-gene, it should be s considered a candidate for gene pyramiding together with the 2 major QTLs identified as a means of deploying the most durable and cost effective breeding strategy for controlling C. lindemuthianum in Zambia with Bukoba as the
source of resistance especially in the yellow bean class.
Description
Thesis of Master of Science in Plant Breeding and Seed Systems - Crops.