Genetic variability and relationships of yield and yield-related traits in locally grown common bean (Phaseolus vulgaris L.) genotypes in Burundi

Abstract

Common bean ( Phaseolus vulgaris L.) is a key food legume contributing to nutrition, food security, and income in Burundi. However, limited information on genetic variability, trait relationships, and genotype × environment interaction (GEI) constrains its effective use in breeding programs. This study assessed phenotypic variability, genetic parameters, trait associations, and breeding potential of bush and climbing bean genotypes. A total of 167 genotypes (83 bush and 84 climbing) were evaluated across multiple environments. Growth habits were analyzed separately using combined ANOVA, REML-based variance components, correlation, path analysis, and GGE biplot approaches. Combined ANOVA revealed highly significant ( P < 0.001) genotypic effects and strong GEI. REML analysis showed higher heritability in bush beans, particularly for plant height (H² = 0.45) and hundred seed weight (H² = 0.51), whereas climbing beans exhibited lower estimates (0.03–0.38). Correlation and path analyses identified number of pods per plant (NPP), harvest index (HI), and hundred seed weight (HSW) as major contributors to grain yield. In bush beans, days to maturity, plant height, and HI had stronger direct effects, while in climbing beans NPP, HI, and HSW were more influential. GGE biplot analysis showed greater yield stability in bush beans, whereas climbing beans exhibited stronger genotype specialization. Mean grain yield exceeded 2700 kg ha⁻¹ in elite bush genotypes and 2500 kg ha⁻¹ in climbing types. BLUP analysis identified stable, high-yielding genotypes including Amahatanyovu, Magoma, Musosi, and Ruvyibushabatama. These findings highlight distinct genetic architectures between growth habits and provide guidance for breeding, though further validation is required.