Potencial sinérgico de cultivares de feijoeiro-comum e bactérias fixadoras de nitrogênio.

Abstract

Nitrogen is the most demandednutrient by common bean plants, as well as by other legumes. Although it has the ability to symbiotically associate with diazotrophic bacteria, this capability is often underestimated due to the significantvariability in biological nitrogen fixation (BNF) efficiency. Achieving a quantitative, precise, and non-destructiveevaluation of variablescorrelated with yield is imperative for optimizing crop productivity. Remote sensing emerges as a promising alternative for such evaluations, with vegetation indicescommonlyapplied due to their ability to estimatebiophysicaltraits and yield potential.The objective of this studywas to evaluate the combining ability of common bean cultivars for BNF, vegetative development, and the correlation of vegetative indices with biophysicalcharacteristics in cultivars inoculated with different strains of Rhizobium. Threeexperimentswereconducted – one in the greenhouse of the Federal University of Lavras (UFLA) and two in the field in the municipalities of Lavras and Carrancas, MG.In the greenhouse, 15 common bean cultivars and threeRhizobium strains were evaluated for general and specificcombining ability. At full flowering, assessments included the SPAD index, aboveground and root dry matter, viablenoduleratio, nodule dry matter, and total N in leaves. Based on general combining ability, seven common bean cultivars and one strainwereselected for fieldtesting.In the field, evaluationswereconducted at variousstages, includingheight, width, and SPAD index at 25, 35, 50, and 65 daysaftersowing (DAS). At full flowering, nitrogen content, nodule dry matter, fresh and dry matter of aboveground and root weremeasured. Harvest parametersincluded the number of pods, weight of one hundredgrains, and grain yield.In Lavras, at 50 DAS aerial images obtained with a Phantom 4 Pro Advanced drone with an RGB sensor were also included. From the digital images, vegetation indices such as GLI, MPRI, and VARI, and canopycoverage with pixel countingwerecalculated.Diallel analysis between cultivars and Rhizobium strains revealed a predominance of additiveeffects in traits related to BNF. Variabilityamong common bean genotypes indicates potential genetic gain in selection for an increase in BNF capacity. Rhizobium inoculation wasfound to promote yield increments similar to mineral fertilization, with strain UFLA 02-100 showing potential for use as an inoculant in the common bean crop.While GLI, MPRI, and VARI indicesdid not exhibit a significantcorrelation with nitrogen content in common bean plants, estimatingcanopycoverage using pixel countingproved to be efficient and showed a significantcorrelation with grain yield. This indicates it as a feasibleoption for assessing the vegetative vigor of this crop.