Genome-wide Association Analysis of Root Traits at Seedlings Stage under Low Phosphorus Stress in Soybean(Glycine max L.)
Soybean is a phosphorus loving crop,the lack of phosphorus can lead to reduced soybean yields or even prevent normal growth.Soybean root traits are an important index to identify soybean tolerance to low phosphorus,therefore,it is particularly important to explore the related genes regulating the function of low phosphorus stress in soybean to improve the low phosphorus tolerance and soybean breeding.In this study,206 soybean germplasm resources were used for phenotypic identification of root morphological traits under low and normal phosphorus treatments.In the low phosphorus treatment,root weight,total root length,root total surface area,root total volume,as well as relative root weight,relative total root length,relative root total surface area,and relative root total volume were utilized as indicators for assessing low phosphorus tolerance traits.A genome-wide association study(GWAS)was performed based on 93 436 SNPs(single nucleotide polymorphisms)to screen significant associated SNPs loci and mine candidate genes.The results indicate significant variations in phosphorus tolerance among different soybean germplasms.Under low-phosphorus conditions,the range of variation in root weight,total root length,root total volume,and root total surface area is 0.04 to 0.75 grams,700.95 to 4300.12 centimeters,0.96 to 8.56 cubic centimeters,and 91.54 to 614.58 square centimeters,respectively.The relative root weight,relative total root length,relative total root volume and relative total root surface area ranged from 0.34 to 2.07,0.49 to 1.78,0.52 to 1.96 and 0.4 to 1.67,respectively.Genome-wide association analysis identified a total of 49 SNPs loci significantly associated with soybean phosphorus tolerance.Among them,10 SNPs loci were associated with root weight,root total surface area,and root total volume under low phosphorus treatment,while 39 SNPs loci were associated with relative root weight,relative root length,relative root total surface area,and relative root total volume.By haplotype analysis and LD block analysis,two candidate genes were obtained,which were specifically expressed in the root for encoding phosphopanethynyltransferase and α-glucan phosphorylase.The results of qRT-PCR showed that the expression levels of GmYB1 and GmYB3 in low-P tolerant varieties were significantly higher than those in low-P sensitive varieties after low-P treatment.The findings of this study provide a theoretical reference and genetic resources for a deeper understanding of the molecular mechanisms underlying soybean tolerance to low phosphorus stress.
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