Combining abilities of soybean progenies and bradyrhizobium strains for biological nitrogen fixation

We aim to study the biological nitrogen fixation (BNF) ability of soybean (Glycine max) progenies and their ability for symbioses using different Bradyrhizobium strains, as well as select progenies and strains that are more efficient in BNF to guide strategies in soybean breeding. An experiment was conducted in a greenhouse, evaluating 24 soybean progenies and five Bradyrhizobium strains. Mean values from analysis of variance were compared by the Scott-Knot test, and partial diallel analysis was performed to estimate general and specific combining ability. Following analysis of the greenhouse experiment, 10 soybean progenies and two Bradyrhizobium strains (SEMIA 587 and INPA 03-11B) were selected to carry out a field trial experiment. Biological nitrogen fixation was affected by genotype, strain, and genotype x strain interactions. Additive effects were predominant on the traits related to BNF, indicating that recurrent selection could be an effective breeding strategy. The progenies showed higher values for the traits related to field nodulation but did not improve seed yield. The EA-8 progeny stood out for high yield and had good results in traits related to BNF and early maturity. The INPA 03-11B strain had the best result for seed yield, indicating high potential for use as an inoculant in soybean crops.