Genome-wide association analysis for drought tolerance and associated traits in faba bean (Vicia faba L.)

Abstract

Faba bean (Vicia faba L.) is an important high protein legume adapted to diverse climatic conditions with multiple benefits for the overall sustainability of the cropping systems. Plant-based protein demand is being expanded and faba bean is a good candidate to cover this need. However, the crop is very sensitive to abiotic stresses, especially drought, which severely affects faba bean yield and development worldwide. Therefore, identifying genes associated with drought stress tolerance is a major challenge in faba bean breeding. Although the faba bean response to drought stress has been widely studied, the molecular approaches to improve drought tolerance in this crop are still limited. Here we built on recent genomic advances such as the development of the first high-density SNP genotyping array, to conduct a genome-wide association study (GWAS) using thousands of genetic polymorphisms throughout the entire faba bean genome. A worldwide collection of 100 faba bean accessions was grown under control and drought conditions and 10 morphological, phenological and physiological traits were evaluated to identify single nucleotide polymorphism (SNP) markers associated with drought tolerance. We identified 29 SNP markers significantly correlated with these traits under drought stress conditions. The flanking sequences were blasted to the Medicago truncatula reference genomes in order to annotate potential candidate genes underlying the causal variants. Three of the SNPs for chlorophyll content after the stress, correspond to uncharacterized proteins indicating the presence of novel genes associated with drought tolerance in faba bean. The significance of stress-inducible signal transducers provides valuable information on the possible mechanisms underlying the faba bean response to drought stress, thus providing a foundation for future marker-assisted breeding in the crop.

Association mapping of plant structure and yield traits in faba bean (Vicia faba L.)

“…The latter accession was also recorded as producing the most stems in this study; therefore, seed production may have been sacrificed for vegetative growth. Seed number per pod was moderately heritable with a broad‐sense heritability of 55%, which is consistent with the result of a previous study 63 where it was reported as 62%.…”

“…Interestingly, 100-seed weight was negatively correlated with seed shape (r = À0.69, p < 0.01) indicating that rounder seeds are often smaller than flattened seeds (Table S7). Broadsense heritability for 100-seed weight was previously reported as 66% 63 and 99%, 37 which is consistent with our work (89%). These results indicate that direct selection based on mean weight would be an effective way to improve this trait.…”

“…for vegetative growth. Seed number per pod was moderately heritable with a broad-sense heritability of 55%, which is consistent with the result of a previous study 63 where it was reported as 62%.…”

“…Pod number per plant had one of the highest broad‐sense heritability for the quantitative traits (89%) and was strongly correlated with seed yield ( r = 0.78, p < 0.01; Table S7). In a previous study, strong positive correlations were reported between pod number per plant and seed number per plant (92%, p < 0.001), as well as plot yield (67%, p < 0.001) 63 . These results indicate that direct selection for pod number could be useful for increasing seed yield in breeding programs.…”

“…In a previous study, strong positive correlations were reported between pod number per plant and seed number per plant (92%, p < 0.001), as well as plot yield (67%, p < 0.001). 63 These results indicate that direct selection for pod number could be useful for increasing seed yield in breeding programs. However, other studies indicated that the pod set was highly dependent on the environment with very low broad-sense heritability estimates (2%-3%).…”