Genetic Factors Associated With Nodulation and Nitrogen Derived From Atmosphere in a Middle American Common Bean Panel.

Atena Oladzad,Abiezer González,James Beaver,Consuelo Estevez De Jensen,Raul Macchiavelli,Phillip Mcclean,Tim Porch

doi:10.3389/fpls.2020.576078

Abstract

Among grain legume crops, common beans (Phaseolus vulgaris L.) are considered to have poor biological nitrogen (N2) fixation (BNF) capabilities although variation in N2 fixing capabilities exists within the species. The availability of genetic panel varying in BNF capacity and a large-scale single nucleotide polymorphism (SNP) data set for common bean provided an opportunity to discover genetic factors associated with N2 fixation among genotypes in the Middle American gene pool. Using nodulation and percentage of N2-derived from atmosphere (%NDFA) data collected from field trials, at least 11 genotypes with higher levels of BNF capacity were identified. Genome-wide association studies (GWASs) detected both major and minor effects that control these traits. A major nodulation interval at Pv06:28.0–28.27 Mbp was discovered. In this interval, the peak SNP was located within a small GTPase that positively regulates cellular polarity and growth of root hair tips. Located 20 kb upstream of this peak SNP is an auxin-responsive factor AUX/indole acetic auxin (IAA)-related gene involved in auxin transportation during root nodulation. For %NDFA, nitrate (NO3−) transporters, NRT1:2 and NRT1.7 (Pv02:8.64), squamosa promoter binding transcriptome factor (Pv08:28.42), and multi-antimicrobial extrusion protein (MATE) efflux family protein (Pv06:10.91) were identified as candidate genes. Three additional QTLs were identified on chromosomes Pv03:5.24, Pv09:25.89, and Pv11: 32.89 Mbp. These key candidate genes from both traits were integrated with previous results on N2 fixation to describe a BNF pathway.

Highlights

Common bean (Phaseolus vulgaris L.) is a major crop of smallholder farmers in Latin America, the Caribbean, and Eastern and Southern Africa
The results demonstrated that nodule number is a heritable trait, and Bliss (1993) suggested that nodule number could be used as a criterion to estimate biological N2 fixation (BNF) capacity
The BNF capacity of a legume is associated with nodulemediated nitrate (NO3−) production and general NO3− uptake and mobilization

Summary

Introduction

Common bean (Phaseolus vulgaris L.) is a major crop of smallholder farmers in Latin America, the Caribbean, and Eastern and Southern Africa In these regions, common beans are often grown on soils deficient in nitrogen (N2; Fenta et al, 2020) and among grain legumes, the species has a relatively low biological N2 fixation (BNF) capacity (Mnasri et al, 2007). Common bean is considered a poor N fixer, genetic diversity for N2 fixation exists within the species This diversity enables the selection of germplasm with enhanced BNF capacity (Buttery et al, 1987; Barron et al, 1999; Farid et al, 2017; Kamfwa et al, 2019). The results demonstrated that nodule number is a heritable trait, and Bliss (1993) suggested that nodule number could be used as a criterion to estimate BNF capacity

Objectives

Methods

Results