Adriano Moreira Knupp

Wild common bean accessions represent an important source of genetic variability for improving biological nitrogen fixation (BNF). The aims of this study were to estimate genetic parameters of lines developed under rhizobial inoculation conditions, obtained by backcross between an elite line and a wild accession, and to select high-yielding carioca common bean lines adapted to these conditions. A total of 95 lines derived from a cross between the elite line CNFC 10762 and the wild accession G2k3499A, followed by one backcross to the elite parent, were evaluated. The lines and three check genotypes were evaluated in the 2019 and 2020 winter crop seasons in Santo Antônio de Goiás, GO, Brazil, under BNF-based systems (rhizobial inoculation and absence of mineral nitrogen) using a randomized block design with three replications. Yield, grain appearance, and 100-seed weight were evaluated. Genetic variability was observed among lines, with some exceeding the CNFC 10762 line (1,877 kg•ha-1) and the Pérola cultivar (1,724 kg•ha-1). Heritability estimates were 59% for yield, 78% for 100-seed weight, and 80% for grain appearance, indicating favorable conditions for selection. Notable gains were achieved through simultaneous selection of the best lines for the traits evaluated (6.7% for yield, 15.4% for grain appearance, and 1.5% for 100-seed weight). Six superior lines combining high grain yield (1,835–2,147 kg•ha-1), favorable grain appearance (1.2–1.0), and 100-seed weight (21.1–22.6 g) were identified, confirming the potential of wild germplasm to broaden the genetic base and contribute to developing carioca common bean cultivars better adapted to BNF.

This study aimed to evaluate whether managing populations and progenies of black common bean (Phaseolus vulgaris L.) in exclusive symbiotic nitrogen fixation (SNF) systems, which refer to environments where the primary nitrogen source in the soil is the SNF, is efficient for selecting lines with high symbiotic performance, using grain yield as a selection criterion, and to verify the relationship between agronomic‐ and SNF‐related traits. A total of 76 black common bean lines from a single population and five checks were evaluated during the winter seasons of 2021 and 2022 under SNF systems. The experimental design was a 9 × 9 triple lattice. Evaluated traits included yield, 100‐seed weight, and grain appearance. The top 10 and bottom 10 lines were selected based on grain yield in the field and evaluated with rhizobia inoculation in two greenhouse trials with five checks, using a randomized block design with four replications. Traits assessed included chlorophyll content, shoot and root dry weight, nodule number, nodule dry weight, and specific nodule weight. Genetic variability among the lines allowed for the selection of genotypes with high symbiotic performance. Significant differences were found between the groups of top and bottom lines for specific nodule weight, indicating its potential as a selection indicator. Significant correlations were found among the traits. Specific nodule weight, chlorophyll content, and shoot dry weight were identified as key factors for the indirect selection of genotypes with better symbiotic performance. Eight lines were selected for advanced trials to develop black common bean cultivars for SNF.

The objective of this work was to select parents and segregating populations of black common bean developed under a biological nitrogen fixation system. Twenty-eight segregating populations were obtained from complete diallel crosses among eight parents with black grains, a high yield, and a high potential for biological fixation. The segregating populations were evaluated for grain yield and 100-grain weight in four environments, where the main source of nitrogen was rhizobial inoculation. The diallel analysis indicated a predominance of additive effects for 100-grain weight and of nonadditive effects for grain yield. Parents 'BRS FP403', CNFP 15188, and 'BRS Esteio' showed the highest general combining ability estimates for 100-grain weight, whereas parents 'BRS Esplendor' and CNFP 15310 were the most suitable for forming populations with a higher yield in biological fixation systems. The 'BRS FP403'/'BRS Esplendor' and 'BRS FP403'/CNFP 15310 populations combined good mean estimates and specific combining ability for both evaluated traits, which makes them promising for the extraction of superior lines for cultivation in production systems without chemical nitrogen fertilization and with nitrogen supply predominantly through biological fixation.