中国小麦条锈菌新毒性菌系出现与有性过程的关系研究

Wheat stripe rust, caused by Puccinia striiformis f.sp. tritici (Pst), is one of the most destructive diseases of wheat-planting areas in China. Application of resistant cultivars is a useful approach for the disease control. However, virulence variation of the pathogen often causes the loss of resistances of cultivars. Since the sexual process of Pst has not been found in the past, the virulence variation of the pathogen at the sexual stage has been neglected for a long time. In recent years, the US scholar verified that barberry (Berberis spp.) is an alternate host of Pst in greenhouse experiment conditions, which provided a basis for studying sexual reproduction of Pst. Therefore, the present study focus on sexual reproduction of Pst, to explore the the effect on new virulent strains emerge during this stage and the coalescent of the new ones, by combining biological methods with molecular techniques, dealing the new virulent strains within race cross on Berberis spp., then using their progenies as parents for interrace cross, and constructing urediospores populations. Base on virulence phenotype and molecular genotype anlysis of these populations, to clarify the effect of sexual stage on new virulent pathotypes emergence, the relationship and evolution between the new virulent ones with other reported races, and the Pst populations contaction on barberries and on wheats. The completion of this project will further improve the epidemic system of wheat stripe rust in China, reveal the major factor of new virulent races formation, and provide scientific support for drawing up strategies for sustainable controlling wheat stripe rust by using possilbe gene deployment of wheat cultivars, predicting new races,and anticipatory breeding of cultivars with high resistance.

条锈病是中国小麦上最严重的病害之一，种植抗病品种是防治该病害的有效措施。然而，条锈菌毒性变异常导致品种抗性丧失。条锈菌有性阶段过去未被发现，其有性生殖在病菌毒性变异中的作用长期被忽视，近期发现小檗可作为条锈菌转主寄主，使其有性研究成为可能。本项目以有性生殖在中国小麦条锈菌新毒性菌系产生中的作用及新毒性菌系的溯源为主攻点，通过新毒性菌系小种内自交及其后代小种间杂交，构建自交后代及杂交后代单夏孢子堆群体，在毒性表型及分子基因型分析的基础上，明确条锈菌有性过程在我国条锈菌新毒性菌系产生中的作用、新毒性菌系与已知条锈菌小种间的演化关系以及我国小檗上的条锈菌群体与小麦上条锈菌群体间的关系等关键问题。本项目的完成将进一步完善我国小麦条锈病的流行体系、揭示我国小麦条锈菌新毒性菌系形成原因，可为我国小麦条锈病的持续控制、新小种预测、前瞻性小麦抗病育种、抗病品种的合理利用及条锈病防控技术的研发提供科学依据。

条锈病是小麦生产上危害最重的气传真菌病害，可造成10%-30%的产量损失，甚至绝收。利用抗病品种是防治该病害最为经济、有效、环保的措施。然而，条锈菌致病性不断变异产生新毒性小种，常常导致品种抗病性“丧失”，病害频繁流行成灾，严重威胁着小麦生产安全。早期研究发现，陇南与川西北等西部地区是我国条锈病的菌源基地和条锈菌新毒性小种的策源地，是条锈病防控的关键区域。然而，关于病菌变异途径与规律、“越夏易变区”新菌系产生原因等一直不清，缺乏针对性病害关键防治技术。. 繁殖小麦条锈菌过程中发现的另一种真菌在扫描电镜下进行观察能侵染小麦条锈菌的夏孢子。结合光学显微镜和电子显微镜的形态学观察，以及分子数据系统发育分析，最终确定这种能寄生于小麦条锈菌夏孢子的真菌是枝孢属枝状枝孢 (Cladosporium cladosporioides (Fresen.) GAde Vries)。又对其进行了重寄生的柯氏法则检验。该菌能够减少夏孢子的数量以及生存能力，是条锈病生物防治的潜在生防资源。. 基于小麦条锈菌夏孢子全基因组序列设计了100 对候选简单重复序列（SSR）引物，最终筛选得到20 对多态性好并且扩增稳定的微卫星标记。以期更好应用于小麦条锈病菌的群体遗传学研究。. 结合毒性和分子数据分析表明，新疆小麦条锈菌群体毒性结构丰富，既有历史曾经流行小种，又有当前流行小种，还有未报道小种，并且遗传多样性水平极为丰富。系统发育树构建和聚类分析揭示新疆地区是一个独立的条锈病流行区，而且与内地和西藏群体间的基因交流较少，这些研究结果对指导新疆乃至全国小麦条锈病的防治具有重要的指导意义。. 系统揭示小麦条锈菌致病性变异规律与机理，为新小种的预测和抗病品种预见性的选育提供依据。通过致病性遗传分析，发现条锈菌致病位点高度杂合，有性后代致病性高度变异，变异率达68.6%-78.3%，其中20%以上后代菌系的致病性强于亲本菌系；构建了首个条锈菌无毒基因的遗传连锁图谱，并揭示了条锈菌无毒基因复杂的遗传表现与规律，为流行小种致病性变异趋势预测和前瞻性抗病育种提供理论依据。