油菜磷高效QTL LRNLP-A3的精细定位和克隆

Phosphorus (P) de?ciency in soils is a major limiting factor for crop growth worldwide. Oilseed rape (OSR, Brassica napus L.) is one of the important oil crops in China, which needs more phosphorus(P) and shows more sensitive to low P than other crops. P-efficiency is a complex quantitative trait.Previous results showed that root morphology and architecture traits,such as root length and root dry weight play important roles in the P uptake and shoot growth. A major P-efficient quantitative trait loci (QTL), LRNLP-A3 for lateral root number had been identified colocated with root and shoot dry weight with TN DH population at low P, which derived from a cross between Tapidor (a P inefficient cultivar) and Ningyou7 (a P efficiency cultivar). To elucidate the genetic control of tolerance to P de?ciency in Brassica napus, fine mapping and cloning of QTL LRNLP-A3 will be conducted using near isogenetic lines (NILs) of OSR. Our strategy is as follows, (1) the flanking markers of the QTL will be used to screen the reciprocal introgression lines, N-BC4, to construct NILs of LRNLP-A3; (2) 'genotype-phenotype' analysis will be conducted to find the recombinant lines and fine mapping the QTL based on developing molecular markers from the genes sequence information of the homologous region in Brassica rapa and developing a segregation population with more than 10 000 lines. (3) the candidate genes will be identified based on the bioinformation analysis and candidate-gene association analysis.(4) over-expression and RNAi of candidate genes will be used to confirm the function of LRNLP-A3 in relation to lateral root number, lateral root length, root and shoot dry weight and P uptake. These results will partially reveal the genetic basis of tolerance to P de?ciency and will be of use in breeding new OSR varieties with improved root growth and seed yield as well as P uptake efficiency.

土壤缺磷是作物生长的主要限制因子之一。油菜是我国重要的油料作物，需磷较多，对缺磷敏感。油菜磷高效是复杂的数量性状，以根长和根重为主的根系特性对油菜磷的吸收，促进地上部生长发育起着很重要的作用。我们已经利用磷高、低效品种构建的TN DH群体定位了油菜磷高效QTL，其中低磷侧根数主效QTL LRNLP-A3与低磷根干重和地上部干重等QTL共定位。在初步定位的基础上，本研究拟利用LRNLP-A3两侧紧密连锁的分子标记，筛选双向导入系群体N-BC4构建LRNLP-A3的近等基因系，利用LRNLP-A3置信区间对应的白菜基因组同源序列开发分子标记进行精细定位；通过生物信息学分析和关联分析等确定LRNLP-A3的候选基因，然后在拟南芥和油菜中对候选基因进行超量和RNAi抑制表达，验证候选基因的功能。研究结果将为解析油菜磷高效的遗传机制，通过分子育种和转基因等现代生物技术改良油菜磷的吸收效率奠定基础。

土壤缺磷是作物生长的主要限制因子之一。油菜是我国重要的油料作物，需磷较多，对缺磷敏感。油菜磷高效是复杂的数量性状，以根长和根重为主的根系特性对油菜磷的吸收，促进地上部生长发育起着很重要的作用。前期。我们利用磷高、低效品种构建的BnaTNDH群体定位了油菜磷高效QTL，其中低磷侧根数主效QTL LRNLP-A3与低磷根干重和地上部干重等QTL共定位。本研究在此基础上，构建了基于SNP标记的甘蓝型油菜高密度遗传连锁图谱（BnaTNDH2041 map） ，利用该图谱对琼脂和纸培系统不同磷水平根系性状的QTL进行精细定位和整合。根据导入系N-BC4F2的简化基因组测序（GBS）得到的基因型数据，利用QTL LRNLP-A3所在物理位置筛选导入系N-BC4F2，共得到3个导入qLRNLP-A03的株系构建近等基因系。关联分析共检测到285个与油菜根形态构型性状显著关联的SNP位点，其中9个SNP与甘蓝型油菜BnaTNDH群体定位的根系形态构型QTL共定位。A03染色体低磷主根长、侧根数量、侧根长、平均侧根长、主根长、根干重、地上部干重关联位点在2.563 Mb-2.702 Mb与低磷主根长A03染色体上的QTL的物理位置相同。分离克隆了甘蓝型油菜A03连锁群响应低磷根构型的4个候选基因，分别为BnaA03g05800D，BnaA03g05820D，BnaA03g05830D 和 BnaA03g05850D。这4个基因包含的8个相邻的SNP形成了一个单倍型 BnA3Hap，该单倍型可以解释缺磷处理9.2%的主根长，6%侧根数目、12.4%侧根长度、6.3%平均侧根长、13.8%总根长、14.5%根系干重和5.9%地上部干重等表型变异。具有单倍型BnA3Hap 6 （GAAAAAGG）的品种主根长、侧根数、总根长等均最长（大），而具有单倍型BnA3Hap 2（AGCCGAGG）的品种上述性状均较短（小）。此外，研究还揭示了磷高效品种宁油7号和磷低效品种Tapidor育种过程中根形态构型等重要农艺性状遗传位点的选择和有利基因群的传递过程。A03连锁群4个候选基因形成的“BnA3Hap”单倍型对理解磷和根系的互作，通过分子育种和转基因等现代生物技术改良油菜磷的吸收效率具有重要的意义。