不同地理和寄主来源的串珠镰孢的营养体亲和性研究

Vegetative compatibility of Fusarium moniliforme strains from different localities and hosts

选用107个采自安徽、山东、江苏、湖北等不同地区棉花、玉米、水稻的串珠镰孢Fusarium moniliforme菌株,在含KClO3培养基上诱导筛选获得抗氯酸盐、不能还原利用硝酸盐的突变株(nitmutant)1081株,在MM、NM、HM等3种不同氮源培养基上划分出nitA、nitB、nitC、nitD四种突变类型,其中nitA出现频率最高,占总体76%;nitB和nitC其次,分别占12%和10%;nitD最少,占总体2%。采用nit突变体互补型配对技术,将供试菌株分别按地理来源和分离寄主进行配对培养,测得不同寄主群体内菌株的营养体亲合群(VCGs)数为56个,然后从每个VCG中随机抽取1个样本菌株,测定不同群体间菌株的VCG同一性,发现所抽取的56个菌株分属于54个VCGs,其中来自棉花的菌株Fm1、Fm2分别与来自玉米的菌株Fm19、Fm20属于同一VCG。按地理来源测定,4个群体共测得55个VCGs,其中来自山东的菌株Fm45和来自安徽的菌株Fm16发生亲和反应,属于同一VCG;107个菌株划分为54个VCGs。结果表明,串珠镰孢菌株群体内存在丰富的VCGs多样性。经多样性分析,不同地理来源的菌株平均1.9454个组成1个VCG,其P与Shannon-Wiener多样性指数分别为0.5140和1.0365;不同寄主上分离的菌株平均1.9107个形成1个VCG,P与Shannon-Wiener多样性指数分别为0.5234和0.9048。经t测验,两个群体Shannon-Wiener多样性指数H值间差异不显著(t=0.70小于t0.05=1.98),说明两个群体的VCG多样性无显著差异,相同地区来源的菌株的遗传相似性与相同寄主来源的遗传相似性相当。

The vegetative compatibility groups （VCGs） of Fusarium moniliforme were tested by applying nitrate nonutilizing （nit） mutant complementation technique to explore the population structure of the important pathogenic fungus. The 107 strains of F. moniliforme were isolated from cotton, corn and rice diseased tissues collected from Anhui, Shandong, Jiangsu and Hubei in China. The tested single-conidium strains were then transplanted on KC103-containing potato sucrose agar （KPS） plates to mutagenize nit mutants and 1081 nitrate-nonutilizing （nit） mutants were recovered from the isolates by transferring chlorate-resistant sectors from KPS plates to minimal medium （MM）. The four mutants types were identified as nit A, nit B, nit C and nit D based on the growing situation of the mutants on MM, nitrite medium （NM） and bypoxanthine medium （HM）, three kinds of different nitrogen media. Among the four types, nit A was the most common one, with the frequency of 76%. Next were nit B and nit C, with the frequency of 12% and 10% respectively. The least one was nit D, 2%. The nit mutants then were paired on MM plates to test the vegetative compatibility of all isolates, according to their geographic location and hosts, respectively. Fifty-six different VCGs were identified totally from all three host-origin populations of the mutants. One sample was taken randomly from each VCG to determine the identity. The result showed isolates Fm1, Fm2 from cotton and isolates Fmlg, Fm20 from corn belonged to the same VCG respectively, while the other strains did not. Similarly, 55 different VCGs were identified totally from all four locality-origin populations of the mutants. Only isolate Fm45 from Shandong and isolate Fm16 from Anhui belonged to the same VCC, while the other strains from different geographic origins belonged to different VCGs. The 107 tested isolates were divided into 54 VCGs, suggesting there was abundant diversity of VCGs in the population of Fusarium moniliforme isolates. The diversity analysis indicated that on the average, 1.9454 isolates from locality-origin population made up 1 VCG; the P and Shannon-Wiener diversity indices were 0.5140 and 1.0365, respectively; and 1.9107 isolates from host-origin population composed 1 VCG on an average; the P and Shannon-Wiener diversity indices were 0.5234 and 0.9048, respectively. The Shannon-Wiener diversity indices （H values） of the two populations were not significantly different from each other based on t test （t = 0.70, below t0.05 = 1.98）. It was suggested that the VCG diversity of the two populations was not significantly different from each other, and the genetic similarity among the isolates from the same locality-origin was equal to that from the same host-origin.