油菜不同根系构型对干旱胁迫的响应及其调控机制研究

Rapeseed (Brassica napus) is one of the most important oil crops in China. However, drought often occurred in Autumn and Spring during its growing season, which resulted in stunted growth, reduced yield and quality. Root plays an important role in water absorption and drought resistance. Root system architecture directly affects water uptake range in the soil. However, there are few researches on the relationship between root system architecture and drought resistance of rapeseed. In this project, germplasms with differed root system architecture were used. The root system architecture of early seedling stage, seedling stage and flowering stage were determined by 2D scanning, 3D root reconstruction and in situ root monitoring system, respectively. The adaptive changes of root system architecture would be revealed, changes of endogenous hormones and gene expression in root would be analyzed. The relationship between root system architecture and water uptake, drought resistance would be elucidated. Also, ideal root system architecture and its supporting parameters which can improve drought resistance of rapeseed would be proposed. Comprehensive analysis of root morphology, root hormone concentration and differentially expressed genes obtained from transcriptome sequencing would elucidate regulatory mechanism of root morphogenesis and responses to drought stress. The research results of this project could be applied in breeding for drought resistant genotypes, and provide theory basis and technical support for drought resistant cultivation.

油菜是中国重要的油料作物之一，在其生长季节内严重的秋旱和春旱时有发生，导致生长受阻及产量品质显著降低。根系在植物吸收水分与抵御干旱中起着至关重要的作用，根系构型直接影响着植株在土壤中吸收水分的范围，与抗旱性密切相关。但是，目前关于油菜根系构型与抗旱性关系了解甚少。本项目拟选用根系构型具有明显差异的油菜材料，结合根系三维重建、根系二维扫描及根系生长监控等不同方法，在干旱条件下进行幼苗期、苗期和花期根系构型的定量测定，揭示不同材料根系构型的适应性变化和差异分析，同时进行根系内源激素变化和基因表达量分析；阐明油菜根构型与水分吸收利用及抗旱性的关系，提出油菜抗旱的理想根构型及其支撑参数。通过综合分析根系形态、根源激素消长及转录组学测序获得的差异表达基因表达量变化，阐明油菜根系形态建成及其响应干旱胁迫的调控机制。本项目研究结果可为油菜抗旱育种及抗旱栽培奠定理论基础，提供技术支撑。

油菜是中国重要的油料作物之一，在其生长季节内严重的秋旱和春旱时有发生，导致生长受阻及产量品质显著降低。根系在植物吸收水分与抵御干旱中起着至关重要的作用，根系形态直接影响着植株在土壤中吸收水分的范围，与抗旱性密切相关。本项目通过系统研究不同根系构型油菜材料对干旱胁迫的响应以及应答机制，对通过根系构型进行遗传改良提供了重要的油菜材料和候选基因，最终对提高干旱条件下油菜产量具有重要意义。主要研究结果如下：.1 两个油菜根系突变体的抗旱性较野生型材料强，但表现有不同。通过采用宁油7号（WT）和其主根突变体（prl）和侧根突变体（lrn）为试验材料，进行苗期和花期盆栽干旱胁迫试验和苗期水培（PEG6000模拟干旱）试验，结果表明根系突变体材料可以不同程度增加油菜的抗旱性，但两个突变体对苗期和花期的干旱响应不同。苗期干旱后，lrn的产量与WT和prl相比降低幅度最小，抗旱性最强；而花期干旱后，prl的产量降低幅度最小。.2 干旱胁迫下主侧根发达材料抗旱性较强, 其中主根较长品种更突出。 从504份油菜材料中筛选与WT、主根突变体（prl）和侧根突变体（lrn）根系性状相似的油菜材料各10个进行盆栽试验鉴定根系构型与产量形成的关系。在花期干旱胁迫下，3类油菜材料的单株经济产量都与对照有极显著差异。其中，prl类油菜材料的单株经济产量的抗旱系数最高为0.58，lrn次之，WT最低。.3 转录组分析揭示激素在根系形态建成中起着重要作用。通过对两个抗旱性和根系性状有显著差异的品种进行转录组测序，结果表明主根较长且抗旱性较强的品种中与脱落酸有关的基因表达量较低，但是与生长素、赤霉素、茉莉酸和油菜素内酯有关的基因表达量较高。另外，通过转录组分析确定了与根系性状有关的基因9个。.4全基因组关联分析鉴定了与油菜抗旱及与根系性状相关的候选基因。 采用了10,620,048个高质量SNP对504份油菜进行了基因型鉴定，将基因型与油菜根系、生物量性状进行全基因组关联分析，检测到17个显著关联的位点，其中9个位点与根系性状相关。最终, 在这些位点附近确定了37个与油菜根系性状及抗旱性有关的候选基因。