豇豆等水型与非等水型水分调节行为的遗传基础与基因表达调控解析

Improving drought resistance of crops while keeping the accompanying side effects to the minimum is the ultimate goal for breeders. Isohydric and anisohydric water management are the two main types of water regulatory behaviors related to plant drought resistance, yet little is known so far regarding the genetic basis of the traits. Here we propose to measure the water management behaviors of the mini-core collection of Chinese cowpea germplasm using a high-throughput "physiolomical" assay to reveal the natural variations of isohydrism and anisohydrism traits. We are to use GWAS and bi-parental QTL mapping to locate QTLs controlling parameters including Ψgs50 and θcr that are key to isohydrism/anisohydrism. Using a "functional mapping" approach, we will also map dynamic QTLs for the water management parameters such as Ψleaf and Gs, over the course of drought stress. Comparative transcriptomic analysis will be conducted to reveal the gene regulatory basis underlying the two different water budgeting mechanisms. Candidate gene search will be performed in several high-resolution QTL regions, through a combinatory analysis of the physiolomical, genetic, and transcriptomic data. The locations of the isohydrism/anisohydrism QTLs will also be compared with the known selective signals in the cowpea genome to reveal the impact of selection on this trait. Lastly, we aim to propose the theoretically ideal haplotypes for the Isohydric and anisohydric cowpea varieties that will be useful in future breeding of favored new varieties.

提高作物抗旱性又尽量减少对其它性状的影响是抗旱育种的理想目标。等水型和非等水型水分调节是与植物抗旱性密切相关的两类生理行为，目前其遗传机制尚不清楚。本项目以我国豇豆微核心种质群体（299份）为材料，利用高通量“生理组”方法动态测定各品系响应于土壤干旱的水分调节行为参数，揭示等水型/非等水型自然变异情况。通过GWAS和双亲本QTL作图定位控制半最大气孔导度下叶片水势、蒸腾骤降的土壤临界含水量等关键等水/非等水型性状QTLs；通过“功能作图”定位叶水势、气孔导度等水分生理参数的动态QTLs，揭示其随干旱进程的变化特征。在典型等水型和非等水型材料间开展比较转录组分析，揭示差异形成的基因调控基础。综合生理组学、遗传定位和表达分析结果并结合豇豆参考基因组信息，在高分辨率QTLs区域搜寻候选基因。最后分析豇豆等水/非等水型QTLs与已知驯化选择印迹之间的关系，提出理想的等水型和非等水型豇豆单倍型。

本项目利用高通量PlantArray平台优化建立了豇豆耐旱性精准鉴定技术体系。揭示了我国豇豆微核心种质群体142份豇豆种质在等水型/非等水型水分调节行为上的自然变异，提出了以土壤含水量临界值（θcri）及气孔关闭速率（KTr）来判断等水型和非等水型特征的新方法。在全基因组水平定位了30个控制等水型/非等水型性状的QTL，通过分析QTLs与液泡膜水通道蛋白同源基因的位置关系，发现其缺乏重叠性。通过对两份非等水型种质X466和X25和两份等水型种质X32和G5的转录组分析，发现其根部和叶部组织间基因均发生剧烈的表达变化，基因变化数目最少的有2824个，最多的有11409个。综合本研究结果与前人结论，提出选择与θcri相关性最强的3个位点2_46561、2_43920、2_12695，与KTr相关性最强的两个位点2_07162、2_01480，与荚长主效QTL Qpl.zaas-3和 Qpl.zaas-5以及抗锈病基因Ruv2紧密连锁的分子标记，通过聚合有利等位变异，可以创造理想的单倍型。项目执行期间发表标注项目资助的 SCI 收录研究论文 3篇（其中中科院1区一篇、影响因子 > 5 一篇），获国家发明专利授权1件，计算机软件著作权2件。项目成果在中国园艺学会豆类蔬菜分会年会（2020、2021）等做了口头报告。

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