Variation for nodulation and plant yield of common bean genotypes and environmental effects on the genotype expression

Common bean symbiotic nitrogen fixation provides an ecological and economical alternative to increase bean production but it depends on soil fertility and climate conditions. The objectives of this work were to characterize common bean genotypes for their ability to establish symbiosis under controlled conditions and to study the effect of the environment on the expression of those genotypes. The experiment under controlled conditions was conducted in a greenhouse with 158 genotypes that represented the major dry bean market classes. The field experiment was carried out in six environments with 64 genotypes that were previously selected for their contrasting nodulation ability and/or root development under the controlled conditions experiment. Nodulation, plant, and grain yield data of the bean genotypes were measured in both experiments. There was a significant high variability in plant development responses among the studied genotypes associated with the rhizobial strain inoculated under controlled conditions. Two nodulation phenotypes were observed among the genotypes tested: the big-nodules phenotype (BNO) associated with almost 63% fewer nodules and 58% higher proportion of nodule biomass in the below-ground compartment than the small-nodules phenotype (SNO) with less developed aerial parts. Genotype plus genotype x environment (GGE) biplot model analysis enabled identification of the highest-yielding genotypes for the different environments. The soil chemical factors of these environments were associated with the nodule number or the biomass of the common bean genotypes. Genotypes with a BNO phenotype showed a good plant response, indicating that this phenotype may be more beneficial for plant growth and seed yield in environmental conditions that may limit nodule development. The amplitude of the genotypic variability found in this work confirms the potential for rhizobial symbiosis of adapted bean genotypes, which could constitute a preferential material for initial breeding of symbiotically active lines. The data also indicate the potential of bean breeding to identify environments containing effective strains of rhizobia essential for sustainable agriculture, improving productivity, and maintaining environmental quality.