Abstract
Common bean (Phaseolus vulgaris L.) provides critical nutrition and a livelihood for millions of smallholder farmers worldwide. Beans engage in symbiotic nitrogen fixation (SNF) with Rhizobia. Honduran hillside farmers farm marginal land and utilize few production inputs; therefore, bean varieties with high SNF capacity and environmental resiliency would be of benefit to them. We explored the diversity for SNF, agronomic traits, and water use efficiency (WUE) among 70 Honduran landrace, participatory bred (PPB), and conventionally bred bean varieties (HON panel) and 6 North American check varieties in 3 low-N field trials in Ontario, Canada and Honduras. Genetic diversity was measured with a 6K single nucleotide polymorphism (SNP) array, and phenotyping for agronomic, SNF, and WUE traits was carried out. STRUCTURE analysis revealed two subpopulations with admixture between the subpopulations. Nucleotide diversity was greater in the landraces than the PPB varieties across the genome, and multiple genomic regions were identified where population genetic differentiation between the landraces and PPB varieties was evident. Significant differences were found between varieties and breeding categories for agronomic traits, SNF, and WUE. Landraces had above average SNF capacity, conventional varieties showed higher yields, and PPB varieties performed well for WUE. Varieties with the best SNF capacity could be used in further participatory breeding efforts.
Highlights
The common bean (Phaseolus vulgaris L.) is the most important food legume grown and consumed worldwide
The analysis showed that days to flowering (DTF) and ∆13 C are not associated with %Ndfa, and leaf chlorophyll content at biplot analysis showed that DTF and Δ13C are not associated with %Ndfa, and leaf chlorophyll flowering (SPAD) and hundred seed weight (HSW) have a negative relationship with %Ndfa (Figure 4B)
The current results indicate that there is variation among the Honduran participatory bred (PPB) and conventional bean germplasm in water use efficiency (WUE) traits, and selecting for lower ∆13 C values could be applied to beans in Honduras to generate improved varieties that are more resilient to drought conditions
Summary
The common bean (Phaseolus vulgaris L.) is the most important food legume grown and consumed worldwide. A member of the Fabaceae family, common bean is a predominantly self-pollinating species with a genome size of 587 Mbp and ploidy of 2n = 2x = 22 [1]. The center of origin for common bean is in Plants 2020, 9, 1238; doi:10.3390/plants9091238 www.mdpi.com/journal/plants. Plants 2020, 9, 1238 present-day Central Mexico [2]. Larger-seeded market classes evolved and were domesticated in South America and belong to the Andean gene pool, while smaller-seeded market classes evolved and were domesticated in Central America and belong to the Middle American gene pool [2,3,4,5,6,7]
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