Upright plant architecture traits and their relationship with grain yield in the selection of Mesoamerican common bean lines cultivated at low altitude

The development of common bean cultivars with upright plant architecture and high grain yield meets the needs of bean growers by facilitating culture management and mechanized harvest. The objectives of this study were to evaluate whether Mesoamerican common bean lines differ for upright plant architecture traits and grain yield, analyze correlations between these traits, and to select superior common bean lines based on a selection index. Four experiments were carried out in different years and growing seasons at low altitude (95 m above sea level) in southern Brazil. These experiments were composed of 17 carioca and black bean inbred lines, which are representative of the most widely produced and consumed common bean classes in Brazil. Upright plant architecture was assessed by 12 characters, and the resulting data were subjected to individual and joint analyses of variance, correlation, and selection index (rank sum). A significant effect for genotype and/or genotype x environment interaction was observed for all traits, except for the length of the first internode and hypocotyl diameter. Most plant architecture traits were correlated, indicating that it is possible to reduce the number of traits that need to be evaluated. Grain yield was negatively correlated with the lengths of the fourth (r = -0.574) and fifth internodes (r = -0.641). General adaptation score, insertion of the first pod, and lengths of the fourth and fifth internodes were efficient to characterize upright plant architecture in the common bean. Indirect selection by the shortest length of the fourth and fifth internodes was efficient to increase grain yield. The genotypes LP 11-117, SM 0312, BRS Valente, and Guapo Brilhante were selected based on a rank sum index. These genotypes present upright plant architecture and high grain yield, which is a common bean ideotype suitable for cultivation at low altitude in southern Brazil.