Identification of quantitative trait loci for symbiotic nitrogen fixation in common bean.

KEY MESSAGE: QTL were identified for symbiotic nitrogen fixation in common bean. These QTL were detected in both greenhouse and field studies, and many overlapped with previously reported QTL in diverse mapping populations. Common bean (Phaseolus vulgaris L.) productivity can be improved through the genetic enhancement of its symbiotic nitrogen fixation (SNF) capacity. This study was aimed at understanding the genetic architecture of SNF through QTL analysis of a recombinant inbred line (RIL) population contrasting for SNF potential. The mapping population consisted of 188 F4:5 RILs derived from a cross of Solwezi and AO-1012-29-3-3A that were evaluated for SNF in the greenhouse and field in Zambia. The population was genotyped with 5398 single-nucleotide polymorphism (SNP) markers. QTL for shoot biomass, nitrogen percentage in shoot biomass, nitrogen percentage in seed, total nitrogen derived from atmosphere (Ndfa) and percentage of nitrogen derived from the atmosphere (%Ndfa) were identified. Three QTL for %Ndfa were identified on chromosomes Pv01, Pv04 and Pv09. Five QTL for Ndfa were identified on Pv04, Pv06, Pv07, Pv09 and Pv11. The QTL Ndfa9.1SA identified in the current study overlapped with a previously reported QTL for SNF. A major QTL Ndfa7.1DB, SA (R2 = 14.9%) was consistently identified in two greenhouse studies and overlapped with previously reported QTL. The QTL Ndfa4.2SA identified from the greenhouse experiment is novel and overlapped with the QTL %NB4.3SA, %NS4.2SA and %Ndfa4.2SA from the field experiment. These QTL identified in both greenhouse and field experiments, which overlap with previously reported QTL, could potentially be deployed by marker-assisted breeding to accelerate development of bean cultivars with enhanced SNF.