中国钝叶草种质资源遗传多样性及重要性状的遗传标记研究

St. Augustinegrass [Stenotaphrum Trin.] is a widely used warm season turf grass for home lawns and commercial landscapes, widely distributed in the tropical and subtropical areas of China. As a high quality turf, St. Augustinegrass has many fine characteristics and rich genetic variation. But the studies on genetic diversity and resistance identification were very little, especially China’s St. Augustinegrass germplasm, which limits its wide utilization and adequate protection. In order to meet the urgent need for both landscape of South China and the quick resistance identification of St. Augustinegrass，the following work will be conducted with St. Augustinegrass based on the early stage work: (1) The methods of resistance identification of St. Augustinegrass have been improved; (2) Identification of SSR moleculer markers associated with morphological traits and resistance will contribute to efficient selection of elite cultivars; (3) In theory, the biological characteristics and genetic relationship of St. Augustinegrass would be studied based on turf quality, phenology, ploidy, resistance, and provided the basis for clarifying genetic relationship among St. Augustinegrass, developing protection strategy of wild germplasm, sustainable use, and improvement of St. Augustinegrass; (4) In practice, the specific accessions with different excellent characteristics would be screened by compared with released cultivars, and excavated 5-7 domestic St. Augustinegrass accessions with excellent turf quality, high organs reproductive ability, strong resistance, and good adaptability. The selection of Excellent St. Augustinegrass accessions with many superior characteristics will provide the cheap and high quality plant materials for the development of international tourism Island of Hainan and then extending to southern China.

钝叶草是一种重要的暖季型草坪草，广泛分布于热带和亚热带地区，具有许多优良特性和丰富的遗传变异。但其遗传多样性和抗性鉴定方面研究甚少，尚未得到充分的保护和利用。本项目针对华南绿化过程中迫切需要优质抗逆的乡土草坪草这一现状，在广泛收集钝叶草种质资源及已有研究基础上，改进钝叶草种质资源抗性鉴定方法，通过对钝叶草属种质资源的生物学特性和亲缘关系研究，对钝叶草属种质资源进行全面评价，从理论上，阐明中国钝叶草种质资源间亲缘关系，进一步运用SSR标记与外部性状和抗性鉴定结果进行关联分析，寻找重要性状分子标记，为钝叶草种质资源的可持续利用和遗传改良提供试验依据；实践上，通过与对照品种比较分析，筛选出一批特异的种质资源，发掘出5-7个坪用质量优、繁殖性能高、抗性强且适应性好的国产钝叶草优异种质，以服务于海南国际旅游岛的绿地发展，继而推广到华南地区进行国土绿化建设。

钝叶草属（Stenotaphrum Trin.）植物是我国南方重要的经济草类之一，我国拥有丰富的野生钝叶草资源，具有很大的开发潜力。本试验利用国内外收集的91份钝叶草属植物作为试验材料，从形态学性状、DNA分子标记、细胞学倍性鉴定、抗性评价及牧饲用营养价值评价等方面多层次地分析钝叶草种质资源的遗传多样性，研究结果表明：. （1）供试钝叶草种质的形态学性状具有较大的变异，匍匐茎叶长、直立枝叶宽、直立枝叶长、匍匐茎节间长、营养枝高、生殖枝高、花序密度和坪用质量的变异都达到20%以上，钝叶草营养和生殖繁殖特征特性存在显著差异（P<0.05）。供试材料可分为三大类。.（2）运用SRAP和ISSR标记对84份钝叶草材料进行遗传多样性研究：SRAP标记产生的多态性条带为267条，多态性条带比率为97.8%；ISSR标记产生的多态性条带为527条，多态性比率为100%。首次基于RAD-seq技术，用57份钝叶草种质资源开发SNP标记，其中对49份森特钝叶草（S. secundatum）共开发出1280873个SNP位点；8份普通钝叶草（S. helferi）共开发出398155个SNP位点。. （3）在70%遮阴下对钝叶草种质资源进行筛选，获得极端种质为S26和S17（耐阴）和S31和S34（不耐阴）。通过测定钝叶草材料的水分利用效率，筛选出抗旱和敏旱分别为S44和S21；在185mM（NaCl）的条件下，筛选出耐盐和敏盐的分别为S49和S36；筛选出高营养型材料22份；在0.0 mM和5.0 mM氮处理下，筛选出S37和S05分别为耐低氮和敏低氮。. （4）根据流式细胞术鉴定出钝叶草的倍性非常丰富，包含了二倍体、三倍体、四倍体、五倍体、六倍体、七倍体和八倍体。. （5）利用SRAP标记成功构建了6份优异品系和4份品种的DNA指纹图谱。. （6）利用SNP标记与4个形态性状（匍匐茎节间长、直立营养枝高、直立枝叶长和直立枝叶宽）和耐低氮3个指标（坪用质量、枯黄率、地上部干重）进行关联分析，森特钝叶草中共检测到41个SNP位点与形态显著相关（P≤10-5），普通钝叶草中未检测到与形态显著相关的SNP位点。分别得到3个坪用质量显著关联位点、45个枯黄率显著关联位点和18个地上部干重显著关联位点（P<10-3）。