大豆苗期磷高效相关性状的遗传解析及新候选基因挖掘

Soybean is an important grain and oil crop with high phosphorus (Pi) requirement in China, but is sensitive to Pi deficiency in environment. However, Pi deficiency is one of factors that decline soybean yield and quality. In our previous research, a novel major quantitative trait locus (QTL) of Pi efficiency in soybean was identified on chromosome 3 using association population. ① In the present project, we will use a set of newly developed high-density single nucleotide polymorphism (SNP) markers to constructed genome-wide association analysis (GWAS) to confirm QTLs/loci identified in our previous study. ② To further genetically characterize the QTLs/loci identified using GWAS, we generated an experimental F2 population in which the alternate alleles of diallelic SNP were segregating. To achieve this, we outcrossed the phosphorus inefficient Nau52 to high phosphorus efficient material Nau120. Though the phenotyping of the lines of F2: 3, we will select the phosphorus efficient pool and the phosphorus inefficient pool to identify Pi efficiency genetic loci using BSA-Seq. BSA-Seq and linkage mapping will verify the results of high throughput GWAS. ③ Based on the information of GWAS, BSA-Seq, and linkage mapping, we will identifiy the genetic loci of high phosphorus efficient. Then combined with the information of bioinformatics analysis, gene expression analysis, soybean hairy roots transformation experiment and candidate gene association analysis, key genes of Pi efficiency will be screened and identified in the QTL intervals in soybean. ④ In addition, we will develop tighter linkaged molecular markers according the allelic variation located in the candidate segment. This project will provide important theoretical basis and germplasm resources for Pi efficiency molecular breeding of soybean.

大豆是中国重要的粮油作物，其生长需磷多且对磷素缺乏敏感，而土壤中有效磷含量普遍偏低，导致大豆产量品质下降。前期对大豆苗期磷高效相关性状进行初定位，在第三号染色体上检测到一个新的主效QTL位点。为此，本项目拟①开展基于高密度SNP标记的全基因组关联分析，鉴定并验证大豆磷高效的主要QTL/位点；②选取初定位QTL有等位变异的磷高效材料Nau120和磷低效材料Nau52进行杂交获得F2:3家系，利用BSA-Seq分析与连锁分析方法定位磷高效遗传区段；③综合关联分析、BSA-Seq以及连锁分析定位结果，最终明确大豆磷高效性状遗传区段，并结合生物信息学分析、低磷诱导表达分析、大豆根毛转化实验以及候选基因关联分析明确大豆磷高效关键基因；④开发候选区段内与磷效率相关性状紧密连锁的分子标记，应用于大豆磷高效分子育种实践。本研究为磷高效大豆分子育种提供理论基础和种质资源。

大豆是人类食用油和植物蛋白的主要来源，然而土壤缺磷是当前限制大豆生产的一个主要因素。发掘利用耐低磷优异基因资源，选育大豆磷高效品种，提高大豆自身应对低磷胁迫的能力，是解决此问题的有效途径。为了挖掘与磷效率相关的遗传位点，本研究联合关联分析和连锁分析，共同鉴定大豆磷高效相关性状候选基因。共鉴定出132个与磷效率相关性状显著相关的SNPs。鉴定出10号染色体上的4个SNPs (AX-93636685、AX-93636692、AX-93932863和AX-93932874)与+P条件下地上部中磷浓度显著相关。其中AX-93932874的物理位置位于GmAP1的5’非翻译取。将GmAP1在大豆毛根转化中的作用进行了研究。与对照相比，在+P条件下，过表达GmAP1的转基因毛状根P浓度显著降低了32.75%;而在+P和-P条件下，GmAP1转基因毛状根RNA干扰中的P浓度分别提高了38.90和14.51%。对该基因初步功能分析发现该基因通过负向调控大豆毛状根中的磷浓度来影响大豆磷效率。另外对显著相关联的10号染色体上12个SNPs进行单倍型分析鉴定出13个单倍型，其中最优单倍型为Hap9，含有该单倍型的载体材料可为大豆磷高效新品种的培育提供新的资源。综上所述，本项目所鉴定的SNPs和候选基因对提高大豆磷效率具有重要意义。