Identification of new sources of resistance to common bean anthracnose (colletotrichum lindemuthianum) among the common bean (phaseolus vulgaris l.) germplasm in Uganda

Abstract

Bean anthracnose, caused by Colletotrichum lindemuthianum, poses a significant threat to common bean production in Uganda. This study aimed to evaluate the adaptation and resistance levels of common bean genotypes to anthracnose disease and identify new sources of resistance within the local germplasm. Genotype by environment interaction (GEI) plays a crucial role in determining crop performance across diverse environments. To comprehensively understand this phenomenon, multi-environment trials were conducted across four major anthracnose hot-spot regions in Uganda. The study encompassed the evaluation of 260 common bean lines for anthracnose resistance and yield across diverse environments. The analysis of variance (ANOVA) demonstrated significant effects of genotypes, environments, and their interaction on both anthracnose severity and grain yield. The genotype by environment interaction analysis revealed the contributions of these factors to the variability of traits. Furthermore, the Additive Main effects and Multiplicative Interaction (AMMI) model and the Genotype plus Genotype by Environment (GGE) biplot were employed to analyze stability and identify ideal genotypes. Results showed that certain genotypes, such as UNGB 260, UNGB 4964, UNGB 2339, UNGB 1592, and G2333, exhibited high levels of resistance and stability across different environments. The GGE biplot analysis indicated the formation of mega-environments, which provided insights into genotype performance across locations. The identification of stable and resistant genotypes is crucial for developing common bean varieties resilient to anthracnose. The study also investigated the resistance of these common bean genotypes to different races of C. lindemuthianum. The phenotypic data revealed varying levels of resistance to different races, with some genotypes exhibiting moderate resistance to the most virulent race (4041) and higher resistance to other races. In conclusion, this research contributes to the development of common bean varieties with enhanced resistance to anthracnose disease. The findings highlight genotypes that are stable across diverse environments and possess resistance to the prevalent races of C. lindemuthianum. These findings hold significance for improving food security and the livelihoods of smallholder farmers in Uganda. The study emphasizes the importance of considering genotype-environment interaction in breeding efforts and provides valuable insights for future research and breeding strategies to combat bean anthracnose.