Mycosystema. 2009, 28(2): 205-212.
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 KClO3-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 hypoxanthine 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 Fm19, 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 VCG, 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.