野生大豆PI342618B高耐淹性的形态生理机制与QTL/基因体系研究

Soybean is sensitive to water submergence at germination and early seedling stages, so it is important to mine elite gene resources with good tolerance for genetic research and breeding utilization. Our previous studies revealed that a wild soybean accession PI342618B originated from Russia had higher tolerance to submergence than that of all tested cultivated soybean. The major contents of this proposal are: 1) to reveal the morphological and physiological characteristics of the tolerant adaptation to submergence stress using PI342618B and the control; 2) to reveal the genetic component of QTL through linkage mapping and association analysis by using two recombinant inbreed line populations and a population composed of chromosome segment substitute lines and other specific tolerant accessions respectively; 3) to fine mapping major QTL and identify their candidate genes for the submergence tolerance, and to reveal the genetic network for regulated genes to submergence through transcriptome and qRT-PCR analyses by using near isogenic lines; 4) to develop molecular markers to assist the development of new lines with good submergence tolerance. We expect to reveal special adaptation mechanism to the water submergence stress and the genetic differences of the tolerance between the germination and early seedling stage in wild and cultivated soybean, and to mine elite gene for breeding purpose. It might be of great significance to deeply understand the principle of adaptation evolution to submergence tolerance from wild to cultivated soybean, and to provide useful germplasm materials and related methods for submergence tolerance breeding in soybean.

大豆在发芽期和幼苗期对水淹涝害敏感，发掘耐淹基因资源可促进耐淹遗传育种工作。申请人前期研究发现国外引种野生大豆PI342618B在发芽期和幼苗期具有强于栽培大豆的高耐淹特性。本申请拟针对该野生大豆比较研究其种子、幼苗适应淹水逆境的形态解剖、生理生化特点；利用PI342618B衍生的2个重组自交系群体和由染色体片段导入系为主构建的种质群体分别通过QTL连锁定位和关联分析揭示其耐淹性的遗传构成；创建次级群体精细定位耐淹重要QTL并筛选候选基因，转录组与定量PCR分析相结合研究应答淹水逆境的基因调控系统；同时开发分子标记用于标记辅助转育野生大豆耐淹基因，选育耐涝栽培新种质。研究预期揭示野生大豆对不同时期淹水逆境的特殊适应机制，明确其与栽培种质耐淹性的遗传差异，并发掘优异基因用于育种实践。这对深入了解野生和栽培大豆种质耐淹适应进化规律具有重要意义，也可为大豆耐淹分子育种奠定材料和方法基础。

大豆耐涝性是复杂数量性状，表型选择效率较低，耐涝种质发掘工作也较薄弱。本项目针对前期发掘的具有高度耐淹性的俄罗斯野生大豆PI342618B进行形态、生理适应特性及遗传基础研究。主要进展包括：①在明确PI342618B在发芽期、幼苗期具有突出耐淹性基础上，揭示其形态、生理适应特点，转录组分析发现淹水处理下PI342618B基因表达具有特异性，发芽期耐淹性主要与肌醇代谢、脯氨酸代谢、碳水化合物代谢过程和氧化还原过程有关，苗期则与主要核糖体生物合成、谷胱甘肽代谢、氮代谢，类胡萝卜素生物合成、碳水化合物代谢、氨基酸代谢和脂质代谢等相关。②通过 QTL 定位解析 PI342618B高耐淹性的遗传构成，利用NJRINP和NJRI4P群体，检测到与发芽率（GR）、正常苗率（NSR）和电导率（EC）相关的8、7和10个位点，发现位于8号染色体上控制PI342618B种子耐淹性的QTL热点区域，还定位到一个控制种子硬实的主效位点GmHs8；通过GWAS关联分析利用347份栽培品系对大豆种子耐淹性进行关联分析，分别检测到与GR、NSR和EC关联的32、33和34个QTNs，其中包括一个多环境下稳定的耐涝主效位点QTN13。揭示了栽培和野生大豆耐淹性存在遗传差异。③根据定位和转录组结果筛选耐淹性相关候选基因，进一步从PI342618B等材料中克隆出GsGSTU24、GsGSTU42、GmSFT1等基因，发现其在调控大豆耐涝性方面具有重要作用。④对1000余份大豆种质资源进行鉴定，筛选出一批耐涝大豆材料；以PI342618B 等耐涝种质为供体与南农86-4、南农99-6等进行回交，获得8个耐涝新品系并用于育种，育成耐逆新品种南农48。项目发表论文26篇，获批专利1项。本研究明确了PI342618B与栽培种质耐淹性间的遗传差异，发掘出一批优异基因/QTL及其载体材料服务遗传育种实践，也为深入研究野生大豆适应逆境的分子机制奠定基础。