丝核菌的菌丝融合群及其遗传多样性研究的新进展

在介绍丝核菌按其菌丝细胞核相划分为单、双、多核丝核菌三大类,再行菌丝融合分类的基础上,较系统地评述了以生化和分子生物学等手段研究其遗传多样性和系统演化关系的最新进展。     

立枯丝核菌第一融合群的遗传分化

利用12个随机引物对来自云南省不同地理环境的立枯丝核菌Rhizoctonia solani Kuhn第一融合群(AG—1)的13个菌株进行遗传分化关系的研究。结果表明受试菌株被标记的DNA谱带多态性检测率为100％,即受试菌株间几乎无同质的DNA谱带。利用UPGMA法构建分子系统树分析发现,遗传距离0．5将其划分为9个遗传聚类组,遗传距离0．86将其划分为6个遗传聚类组,而遗传距离0．95可将其划分为3个遗传聚类组。结果表明受试AG1融合群的13个菌株具明显的遗传分化。     

立枯丝核菌营养菌丝多型性观察

采用了2种不同的方法对立枯丝核菌营养菌丝的形态进行了观察和比较,观察到2种不同的营养菌丝的形态,即菌核类和假分生孢子类。为以后进一步研究立枯丝核菌营养菌丝的多型性奠定了一定的基础。     

新疆北疆棉田立枯丝核菌菌丝融合群及其营养亲和群研究

从新疆北疆棉区采集了典型的棉花立枯病病苗及棉田土标样686份,按常规分离方法分离得到399个分离物,从中鉴定出272个纯化的立枯丝核菌(Rhizotonia solaniKühn)菌株,经玻片吉姆萨氏染剂(Gimsa′sstain)染色程序观察细胞核数目,全部测试菌株均属于多核。用标准菌株,通过载玻片菌丝融合实验测定,将纯化的272个菌株划归为3个菌丝融合群:AG-2、AG-4和AG-5,分别占总菌株的6.24%、84.2%和1.1%。另有23个菌株不与任何标准菌株融合,占8.46%,说明新疆北疆棉田立枯丝核菌的优势菌系是多核丝核菌的AG-4融合群。通过从10种不同配方的培养基中筛选的效果好的麦芽蛋白胨(MPDA)配方培养基(Ⅱ)进行对峙培养,以建立标准菌株,将纯化获得的272个丝核菌菌株,划分为6个不同的营养亲和群,研究说明新疆北疆地区棉田立枯丝核菌各菌丝融合群内确有不同程度的分化。     

丝核菌的菌丝融合群及其遗传多样性研究的新进展

在介绍丝核菌（Rhizoctonia）按其菌丝细胞核相划分为单、双、多核丝核菌三大类,再行菌丝融合分类的基础上,较系统地评述了以生化和分子生物学等手段研究其遗传多样性和系统演化关系的最新进展。     

棉立枯丝核菌(Rhizoctonia solani)中的一个dsDNA病毒

自从1962年Hollings在栽培蘑菇(Agaricus bisporus)中发现第一例真菌病毒以来,迄今已在100多种真菌中发现了病毒,多数含双链RNA基因组。1972年Bozarth报道在R.solani中发现病毒,但未报道该病毒的理化性质。1975年Finlker在R.solani的一个强致病力菌株中分离到双链RNA病毒,它含3个组分dsRNA。     

外生菌根真菌同立枯丝核菌重寄生关系的研究

研究了18株外生菌根菌对Rhizoctonia solant Kuehn的重寄生作用。在光学显徽镜下观察到8株茵根真菌同R．Solani具有重寄生关系,通常表现为吸附生长,缠绕,侵入,消解等4种作用形式。首次将扫描电镜和能谱仪(EDAX)应用到真菌间相互作用关系的研究上,对3株菌根菌Gomphidius roseus、Lacearia bicolor、Lactarius deliciosus 进行了扫描电镜观察和X-射线微区分析。发现了在吸附生长,缠绕和侵入等3种作用形式中,R. solani和菌根菌菌丝之间有物质流的存在,物质流主要岔有P、S、K、Ca等元素物质,流向是由R. solani菌丝到菌根菌菌丝。而在消解作用中则没有发现这种物质流。     

核酸技术在立枯丝核菌分类与生态学研究中的应用

立枯丝核菌是一种传播广、危害大的土传病原菌,对其展开的研究已涉及各个方面并逐渐深入,近几年借助于核酸技术对其所展开的研究更成为热点。对核酸技术在立枯丝核菌的分类学研究(主要包括G Cmol%含量测定、核酸杂交、各种DNA指纹技术、特异PCR扩增、测序DNA的序列分析)、监测群体动态变化的生态学研究(实时荧光PCR技术)中的应用作一简要的介绍。     

Use of DAPI for Anastomosis Group Typing of Strains of the Fungus Rhizoctonia solani

Strains of Rhizoctonia solani, a common soil-borne, pathogenic fungus of plants, are assigned to one of 11 anastomosis groups (AGs) based on the occurrence of imperfect fusions (anastomoses) between hyphae of a non-typed strain and a tester strain of one of the 11 AG's. Imperfect fusion is characterized by the death of one or more cells in each of the hyphae involved in the fusion. Although hyphae from branches of the same strain of JR. solani may fuse with each other (self-fusion), cell death does not occur. Cell death is accompanied by nuclear degradation and granulation, or plasmolysis of the cytoplasm, which often is not visible using bright-field microscopy. When the DNA-binding fluorochrome DAPI (4', 6-diamidino-2-phenylindole) is used and the hyphal fusions viewed under fluorescence microscopy, no nuclei are observed in fused hyphal cells from two strains of the same AG of R. solani Because DAPI reacts only with living nuclei, lack of staining is presumptive evidence that the fused cells are dead as a result of imperfect fusion. The use of DAPI reduces the time required for making AG determinations compared to standard methods because it eliminates the need to assess cell wall dissolution and cytoplasmic fusion. Also, it is not necessary to trace the hyphae involved in the fusion to their respective origins to ensure that self-fusion has not occurred.     

山东省玉米纹枯菌融合群类型及遗传多样性

从山东省14个县市区采集的玉米纹枯病标本上分离获得103个玉米纹枯菌菌株。核荧光染色确定菌丝细胞核的数目,以及利用配对培养法确定不同菌株细胞是否融合。结果表明这些菌株分别属于多核丝核菌的AG-1-IA、AG-1-IB、AG-1-IC、AG-3、AG-4-HG-I、AG-5和WAG-Z融合群和双核丝核菌的AG-Ba融合群,其中AG-1-IA类型菌株数量占菌株总数的60.19%,为优势融合群。通过inter-simple sequence repeats（ISSR）标记技术进行菌株的遗传多样性分析,获得45个ISSR分子标记,其中91.1%的片段具有多态性,表明种群间存在丰富的遗传多样性。UPGMA聚类分析将103个菌株分成6个遗传聚类群,遗传聚类群的菌株组成说明遗传群组的划分与菌株的地理来源和菌株融合群类型均存在一定的相关性。     

浙皖鄂地区水稻纹枯病菌5个种群的遗传结构分析

水稻纹枯病是世界性的主要病害之一。目前对该病病原菌种群的遗传多样性研究不多,知之甚少,了解其种群的遗传结构可以增加对其进化历程的了解,以制定科学的防治策略。水稻纹枯病菌通常被认为是以无性克隆繁殖为主,但有研究报道它具有混合繁殖方式。有关我国浙皖鄂地区水稻纹枯病菌种群的遗传多样性研究尚未见报道。为了解该地区水稻纹枯病菌种群的遗传变异、基因流、繁育方式及其遗传背景,采用ITS-5.8SrDNA测序技术,分析了分离自浙江富阳(FY)、安徽绩溪(JX)和巢湖(CH)以及湖北荆州(JZ)和孝感(XG)的5个水稻纹枯病菌种群75个菌株的遗传多样性。RhizoctoniasolaniAG-1IA是采集地区水稻纹枯病菌的优势类群。ITS-5.8SrDNA序列经测定共检测到78个多态位点,碱基A、T、C、G的平均含量分别为25.4%、33.6%、21.0%和20.0%。序列的平均转换与颠换比(Ti/Tv)为1.65,其中密码子第3位点的变异最高。根据序列的核苷酸变异共定义了29种单倍型,其中单倍型H5为5个种群的共享单倍型,占样本数的61.33%。5个种群的单倍型多样性和核苷酸多样性分别为0.627和0.482%,显示水稻纹枯病菌种群具有较高的遗传多样性。种群间固定化指数Fst为-0.0253-0.0170,基因流Nm为5.56-11.12,说明种群间基因交流频繁,基因流抑制了由遗传漂变引起的遗传分化,菌丝或菌核短距离扩散和带菌种子远距离传播增加了种群间的基因交流。AMOVA分析显示,种群间的遗传变异仅占总变异的19.03%,而80.97%的变异存在于种群内部,种群间的遗传分化很低。Mantel检验发现,遗传距离与地理距离无显著相关性(r=-0.241,P=0.499)。采用UPGMA法构建的单倍型间的系统发育树表明,不同地点的单倍型分支混合分布,这进一步验证了Mantel检验的结果。单倍型的网状分析显示,水稻纹枯病菌种群曾经发生过种群暴发而不断扩散,因还未能获得足够的时间建立更加复杂的结构故而呈非典型"星状"。采用中性检验分析了水稻纹枯病菌种群遗传结构,结果表明,种群间存在很强的自然选择作用,群体符合Hardy-Weinberg遗传平衡,说明水稻纹枯病菌群体是一个随机交配群体,具有以担孢子进行有性繁殖和以菌丝或菌核进行无性繁殖的混合繁殖方式。这种生物学特性可能是导致其在较小生态范围内较高的遗传多样性水平和较低的种群遗传分化的原因。另外,水稻纹枯病菌经有性繁殖产生新的基因型,并通过无性繁殖在群体内固定繁殖,这种遗传模式极有可能导致其进化潜能提高,极易对杀菌剂产生抗性。因此,对水稻纹枯病菌的防治,除了施用化学药剂和种植抗性品种外,还需要防治农田灌水引起的病原菌(菌丝和菌核)在地区间的流动传播,减少带菌种子迁移或农用机械的交叉污染,对水稻、大豆和玉米等寄主作物的种子进行播前处理等等,这些对于水稻纹枯病菌的防治也是极为重要的。     

First Report of Rhizoctonia solani AG 8 on Wheat in Turkey

A survey was conducted in Ankara and Eskisehir provinces of Turkey for determining anastomosis groups and pathogenicity of Rhizoctonia species associated with root and crown rot of wheat. Pathogenicity tests revealed that Rhizoctonia solani AG 8 caused the common symptoms of damping‐off and stunting.     

广东省水稻纹枯病菌遗传多样性与致病力分化的研究

利用随机引物扩增多态性DNA（PAPD）分子标记技术分析了来自广东省7个县市48个水稻纹枯病菌菌株的遗传多样性,以筛选出的10个随机引物对菌株进行PAPD－PCR扩增,共产生了98个PAPD分子标记,其中89．9％的片段具有多态性。48菌株间的遗传相似性系数（以Nei基因一致度表示）在0．56－0．949之间,用UPGMA和类分析可将它们分为5个RAPD遗传聚类群（A、B、C、D、E）,相同地区来源的菌株基本上聚类在同一组群内。在温室中对供试菌株进行致病性测定,结果表明所有菌株对水稻品种Tetep都有致病性,菌株间致病力差异显著（α＝0．05）,病情指数范围为0．73－18．7,平均感指病指数为5．24。试验分析结果表明水稻纹枯病菌具有丰富的遗传多样性,不同县市的菌株存在很大的遗传分化现象（FST＝0．579）,RAPD遗传聚类群的划分与菌株的地理来源有明显的相关性,但菌株的致病力差异与菌株的来源、遗传聚类组群的划分没有明显的相关性。     

Variations in culture morphology and pathogenicity among protoplast-regenerated strains of Rhizoctonia solani

Abstract Protoplast-regenerated cultures derived from mycelia of cereal-infecting field isolates of Rhizoctonia solani exhibited major variations in cultural morphology and in pathogenicity. Each field isplate yielded three of four distinct morphological types of protoplast cultures. The presence of the new morphological phenotypes was attributed to the selection of homokaryons arising from protoplasts with single nuclei. Highly pathogenic field isolates produced protoplast cultures with higher virulence than those from weakly virulent pathogenic isolates, and homokaryotic strains were generally less pathogenic than the parental field isolate.     

Baseline sensitivity and efficacy of thifluzamide in Rhizoctonia solani

Thifluzamide is a SDHI (succinate dehydrogenase inhibitor) fungicide, which interferes with succinate ubiquinone reductase in the mitochondrial electron transport chain of fungi. Presently, jinggangmycin is the major fungicide extensively used for the control of rice sheath blight caused by Rhizoctonia solani and resistance to jinggangmycin was first reported to occur in China. A total of 128 isolates of R. solani from Anhui Province of China were characterised for the baseline sensitivity to thifluzamide. The isolates were very sensitive to thifluzamide and the baseline sensitivity curve was unimodal with an average EC₅₀ value of 0.058 ± 0.012 µg mL^?1. However, EC₅₀ values of boscalid (another SDHI fungicide) for inhibition of mycelial growth of 22 arbitrarily selected R. solani isolates ranged from 1.89 to 2.68 µg mL^?1. Thifluzamide applied at 110 µg mL^?1 exhibited excellent protective and curative activity against rice sheath blight and provided 81.1–91.0% protective or curative control efficacy. In field trials in 2010 and 2011, control efficacies of thifluzamide at 82 g.a.i ha^?1 15 and 30 days after second application were 84.2% and 86.7%, respectively, suggesting excellent activity against sheath blight. There was a statistically significant difference in the efficacy between thifluzamide and boscalid or jinggangmycin. These results suggested that thifluzamide should be a good alternative fungicide to jinggangmycin for the control of rice sheath blight.