Genetic Diversity Linked to Haplotype Variation in the World Core Collection of for Boron Toxicity Tolerance Provides Valuable Markers for Pasture Breeding.

In alkaline soils in arid and semi-arid areas toxic concentrations of the micronutrient boron (B) are problematic for many cereal and legume crops. Molecular markers have been developed for B toxicity in cereals and . There is a need for such tools in clovers-. To this end, we undertook a genome-wide association study (GWAS) with a diversity panel of subterranean clover ( L.), an established model pasture legume for genetic and genomic analyses for the genus. The panel comprised 124 genotypes (97 core collection accessions and 27 Australian cultivars). Substantial and useful diversity in B toxicity tolerance was found in . Such variation was continuously distributed and exhibited a high broad sense heritability = 0.92. Among the subspecies of , ssp. was most susceptible to B toxicity ( < 0.05). From the GWAS, the most important discoveries were single-nucleotide polymorphisms (SNPs) located on Chr 1, 2, and 3, which mapped to haplotype blocks providing potential genes for a B toxicity tolerance assay and meriting further investigation. A SNP identified on Chr 1 aligned with respiratory burst oxidase-like protein (TSub_ g2235). This protein is known to respond to abiotic and biotic stimuli. The identification of these novel potential genes and their use to design markers for marker-assisted selection offer a pathway in pasture legumes to manage B toxicity by exploiting B tolerance.