基于QTL定位的芒果抗炭疽病分子遗传机制解析

Anthracnose, which occurs frequently during the cultivation and postharvest storage of mango, severely affects the development of mango industry. Analyzing the molecular genetic mechanism of disease resistance and breeding new variety with anthracnose resistance and good quality can solve this prolem effectively. Disease resistance is always a quantitative trait and it may show a genetic link, but there is no report about the QTL (quantitative trait locus) analysis of anthracnose resistance in mango. To clarify the inheritance of anthracnose resistance and linked markers, we have constructed F1 segregated population derived from Jin-Hwang （highly resistant to anthracnose） and Irwin mango (highly susceptible to anthracnose). This F1 population will be used as experimental material in this project. The resistant and susceptible gene pools will be made; The parents, F1 population and two gene pools will be sequenced by using specific length fragments amplified sequencing technology (SLAF-seq), the polymorphic SNP markers will be screened, and the mango high-density genetic map will be constructed by using SNP and EST-SSR molecular markers; QTL associated with anthracnose resistance will be mapped and analyzed through combining the genetic map and disease resistance evaluation result. Results from this study will elucidate the molecular genetic mechanism of anthracnose resistance and provide theoretical and practical foundation for studying disease resistance mechanism and breeding resistant mango varieties.

炭疽病在芒果栽培与采后贮运过程中普遍发生，严重影响芒果产业发展，解析芒果抗病分子遗传机制，创建抗病且品质优良的新种质是解决该问题的有效方法。抗病多为数量性状且可能存在连锁遗传，但芒果抗炭疽病数量性状位点（QTL）相关研究未见报道。为了弄清炭疽病抗性遗传规律及连锁标记，我们构建了金煌×爱文芒果炭疽病抗、感杂交F1代群体，对亲本和176个F1代单株进行了初步抗性鉴定，发现后代存在抗、感分离。本研究拟以此群体为材料，构建F1代群体抗、感基因池，采用特异性长度扩增片段测序技术（SLAF-seq）对亲本、F1代单株和抗、感基因池进行简化基因组测序，筛选多态性SNP，并联合项目组前期开发的EST-SSR构建高密度遗传图谱。在此基础上，结合抗性分离数据的遗传分析结果，实现芒果抗炭疽病QTL定位，初步解析芒果抗炭疽病分子遗传机制，为芒果抗病机制研究与抗病种质创建打下基础，具有理论与实践的双重意义。

炭疽病在芒果栽培与采后贮运过程中普遍发生，严重影响芒果产业发展，解析芒果抗病分子遗传机制，创建抗病且品质优良的新种质是解决该问题的有效方法。抗病多为数量性状且可能存在连锁遗传，但芒果抗炭疽病的数量性状位点（QTL）相关研究未见报道。为了弄清炭疽病抗性遗传规律及连锁标记，本项目采用特异性长度扩增片段测序技术（SLAF-seq）对176 个金煌（抗炭疽病）×爱文（感炭疽病）杂交 F1 代单株、亲本进行简化基因组测序，采用HighMap软件构建了总图距为3,148.28 cM的遗传图谱，该图谱将6,594个SLAF标记定位在20个连锁群上，两个标记的平均距离为0.48 cM,每个连锁群平均包含 330个标记，平均覆盖157.41 cM，连锁群的长度从119.44 cM（LG6）到 206.90 cM（LG19）。同时采用室内叶片接种法对 F1 代单株进行炭疽病抗性鉴定，根据此表型数据并结合构建的图谱，利用MapQTL软件的区间作图法进行了芒果抗炭疽病的QTL分析，共检测到与其相关的QTL 11个，均位于1号连锁群上，每个QTL可以解释表型变异的9.5%-15.4%。通过扫描电镜观察金煌、爱文果实进行炭疽菌接种和不接种处理后的过程及差异，选择处理后0h、36h和72h样品进行转录组学研究，共筛选到差异的转录因子类、泛素化、糖基化、乙酰化等修饰调节基因10余个。这些研宄结果为芒果基因组结构与功能的研究、相关基因的图位克隆及分子标记辅助育种奠定了基础。