【作者】 陈江；

【导师】 张忠军；

【作者基本信息】 中国农业大学 ， 植物病理学， 2014， 博士

【摘要】 小麦(Triticum aestivum L.)在粮食安全问题中占有重要地位。小麦纹枯病在世界很多地区均有加重趋势,尤其是在我国,已被农业部全国农业技术推广服务中心列入“重大”病虫害名单中,其流行面积可与条锈病和赤霉病相提并论,我国小麦纹枯病主要由土壤习居性真菌禾谷丝核菌(Rhizoctonia cerealis)引起。生产上种植的小麦品种均感染纹枯病,没有免疫品种,有的品种则感病程度明显较轻而具有一定程度的数量抗病性。种植抗病品种可以减少杀菌剂的使用、降低生产成本、减轻环境污染。利用纹枯病抗性的途径之一是从小麦种内筛选数量抗病资源及发现抗病数量性状位点(quantitative trait locus, QTL),国内期刊上其他研究人员有6篇文章报道了小麦抗纹枯病QTL。至2014年3月,国际期刊上对小麦抗纹枯病QTL研究的报道只有一例,由本文作者于2013年发表在Theoretical and Applied Genetics上。本研究中首先测定了在山东和陕西2省小麦纹枯病重病区收集的47个小麦推广品种的抗病程度和采集的55个纹枯菌菌株致病力。结果表明,纹枯菌株中的大部分是R. cerealis,多数菌株表现为中等或低等致病力；小麦品种中的多数均严重感染纹枯病,只有6个可能具有中等程度抗病性,与这些推广品种同一批试验中的小麦品种(系)Luke和AQ24788-83(简称AQ)的病情最低。本实验室之前构建了Luke×AQ组合的1589个F8重组自交系(RIL),本文作者从中随机抽取了241个RIL用于纹枯病抗性QTL分析。在温室和田间2种条件下,采用人工接种和自然发病2种方法,共进行了5次试验,测定了这些RIL的病情表现型。与本实验室其他成员合作用这241个RIL构建了含有605个SSR和EST-SSR标记位点的染色体连锁图,是目前国内外报道的含SSR位点数目最多的小麦染色体连锁图。基于这些基因型和表现型数据,发现了11个抗纹枯病QTL,其中7个在5次试验中均稳定地表现抗病作用,根据国际上的通用规则,命名为Qse.cau-1AS, Qse.cau-2BS, Qse.cau-3BS, Qse.cau-4AL, Qse.cau-5DL, Qse.cau-6BL和Qse.cau-7BL,这7个中的4个无疑问是新的抗纹枯病QTL,另外3个也可能是新的QTL。这7个中的6个与小麦株高和抽穗期无关,应属于“抗病”而非“避病”。从Luke×AQ的1589个RIL中随机抽取898个,对其纹枯病病情表现型进行了试验,包括在田间条件下人工接种高致病力菌株和自然发病共4次试验,又对其中的3%极端抗和3%极端感病的共54个RIL在温室条件下人工接菌进行了2次试验,这些试验表明抗/感病性状能够在不同环境/条件下稳定遗传及出现了明显的抗/感病超亲遗传。测定了这898个RIL在7个QTL位点的基因型,分析了其中6个QTL的累加效果,共有64种(26=64)基因组合,从898个RIL中选择出来17个含有所有6个抗纹枯病QTL抗性等位基因(RRRRRR)的RIL,其它63种基因型的病情值显著地高于或不显著地低于RRRRRR的病情。通过QTL累加分析发现,Luke中可能含有尚未被鉴定出来的抗纹枯病QTL, AQ中可能含有抑制抗病QTL表达的因子。又根据用AUDPC度量的病情表现型选择了17个最抗病的RIL,结果表明根据基因型的选择结果与根据表现型的选择结果两者之间高度一致,田间试验结果与温室试验结果两者之间也高度一致。随着QTL数目的累加,AUDPC值逐渐下降。结论是：累加QTL是改良小麦抗纹枯病的一条有效途径。更多还原

【Abstract】 Wheat(Triticum aestivum L.) provides staple food to the human population and constitutes a concern of food security. The disease of sharp eyespot has escalated into a major threat to wheat production in many regions of the world, especially in China where it has been considered by the Ministry of Agriculture as a destructive disease comparable to stripe rust and fusarium head blight. Sharp eyespot is mainly caused by the soil-borne fungus Rhizoctonia cerealis in our country, and no commercially planted wheat cultivar has yet been found to be immune fron the fungus. However, some cultivars exhibit their sharp eyespot intensity much lower than the others, or possess some degree of quantitative resistance to the disease. Wheat resistance to sharp eyespot can be a potential means to reduce the needs for application of fungicides, and thus to save the cost of wheat production and to alleviate environmental pollution. A strategy is to screen the germ plasm resources within wheat species and to map the quantitative trait locus (QTL) for the resistance. Six studies have been reported by several researchers on detection of QTL for sharp eyespot resistance in Chinese journals, while only one report is available in international journal that was reported by the present author in Theoretical and Applied Genetics in2013.In the present study,47wheat cultivars that have been commercially planted widely in the’hotspot’ areas of sharp eyespot in the provinces of Shandong and Shanxi were collected and screened for sharp eyespot resistance, together with some wheat germ plasm resources including Luke and AQ24788-83. The results showed that none of the commercial cultivars were immune from the disease and six of them were moderately resistant to the disease, whereas Luke and AQ24788-83were significantly much less diseased in comparison with all the commercial cultivars. At the same time,55isolates of Rhizoctonia spp. were collected and tested, and it was found that the majority of the isolates were R. cerealis and they showed moderate to weak virulence.The recombinant inbred line (RIL) population of Luke×AQ24788-83was previously constructed in our laboratory consisting of1589F8RILs, from which241ones were sampled by the present author. The241RILs were assessed for sharp eyespot resistance by conducting field and greenhouse trials during the period from2008to2012, and were used to construct a chromosome linkage map containing605simple sequence repeat (SSR) DNA marker loci, the wheat map that has the largest number of SSR loci reported up to date in the world. Analyses based on these phenotype and genotype data found eleven quantitative trait loci (QTLs) to be associated with the sharp eyespot resistance and seven of them expressed consistently across the five trial environments. The seven were designated as Qse.cau-1AS, Qse.cau-2BS, Qse.cau-3BS, Qse.cau-4AL, Qse.cau-5DL, Qse.cau-6BL, and Qse.cau-7BL. Four of these QTLs are unequivocally novel, while it is possible that the other three might also be novel. Plant height and heading date of the241RILs were recorded in the four field trials. All of the seven disease resistant QTLs were independent of plant height and heading time except one that was significantly associated with plant heading time, suggesting that the six QTLs did confer a resistance to the disease instead of an escape from it.A sample of898from the1589Luke×AQ24788-83RILs were evaluated phenotypically for sharp eyespot resistance in four field trials inoculated artificially with a R cerealis isolate of strong virulence or infected with naturally occurring R. cerealis populations. In addition,3%of the898RILs were selected for either extreme resistance (i.e.,27RILs) or extreme susceptibility (another27RILs), and the54RILs were evaluated for sharp eyespot resistance in two greenhouse trials inoculated artificially with a R. cerealis isolate of strong virulenc. These trials showed that the resistance or susceptibility of the RILs was inherited readily across the different experimental environments and that trasgressive inheritance for both resistance and susceptibility occurred. The898RILs were genotyped at the seven detected QTLs, and six of the QTLs were used for examining QTLs accumulation effect. Sixty-four recombinations among the six QTLs (26=64) were compared for the aerea under the disease progress curve (AUDPC). Of the898RILs,17ones had the genotype RRRRRR (i.e., the17RILs had resistant allele at each of the six QTL loci). The mean AUDPC of RRRRRR was significantly lower than or not statistically higher than those of the other63genotypes. Analyses of QTLs accumulation suggested that Luke might harbor some QTLs that have not yet been detected, and that AQ24788-83might harbor some inhibitor or suppresser that might interfere with the expression of the four QTL resistance alleles contributed by AQ24788-83. Seventeen RILs were selected phenotypically for extremely low AUDPC from the898RILs for comparison between the selection based on QTL genotype and the selection based on AUDPC phenotype. The comparison showed a high degree of consistency between the two different selections, and a high degree of consistency between the field trial result and the greenhouse trial result. With the increasement of the number of QTLs accumulated, the AUDPC value decreased steadily. According to these results, I believe that accumulation of QTLs would constitute a strategy for improving sharp eyespot resistance in wheat.更多还原