Genome-wide association and linkage mapping strategies reveal genetic loci and candidate genes of phosphorus utilization in soybean

Insufficient available phosphorus in soil has become an important limiting factor for the improvement of yield and quality in soybean. The mining of QTLs and candidate genes controlling soybean phosphorus utilization related traits is a necessary strategy to solve this problem. In this study, 11 phosphorus utilization related traits of a natural population of 281 typical soybean germplasms and a recombinant inbred line (RIL) population of 270 lines were evaluated under different phosphorus conditions at two critical stages: the four-leaf stage as the seedling critical stage was designated as the T-1 stage, and the six-leaf stage as the flowering critical stage was designated as the T-2 stage. In total, 200 single nucleotide polymorphism (SNP) loci associated with phosphorus utilization related traits were identified in the natural population, including 91 detected at the T-1 stage, and 109 detected at the T-2 stage. Among these SNP loci, one SNP cluster (s715611375, ss715611377, ss715611379 and ss715611380) on Gm12 was shown to be significantly associated with plant height under the low phosphorus condition at the T-1 stage, and the elite haplotype showed significantly greater plant height than the others. Meanwhile, one pleiotropic SNP cluster (ss715606501, ss715606506 and ss715606543) on Gm10 was found to be significantly associated with the ratio of root/shoot, root and total dry weights under the low phosphorus condition at the T-2 stage, and the elite haplotype also presented significantly higher values for related characteristics under the phosphorus starvation condition. Furthermore, four co-associated SNP loci (ss715597964, ss715607012, ss715622173 and ss715602331) were identified under the low phosphorus condition at both the T-1 and T-2 stages, and 12 QTLs were found to be consistent with these genetic loci in the RIL population. More importantly, 14 candidate genes, including MYB transcription factor, purple acid phosphatase, sugar transporter and HSP20-like chaperones superfamily genes, etc., showed differential expression levels after low phosphorus treatment, and three of them were further verified by qRT-PCR. Thus, these genetic loci and candidate genes could be applied in marker-assisted selection or map-based gene cloning for the genetic improvement of soybean phosphorus utilization.