| Fusarium moniliforme Sheld is an economically important plant pathogenic fungus with a wide host range. Based on the isolation and identification of the causal organism of cotton red rot, rice banakae disease, maize ear rot in Anhui, Shandong, Jiangsu and Hubei, the biological characteristics, vegetative compatibility and pathogenicity differentiation, the effect of culture filtrate and crude toxin on cotton growth, esterase isozyme electrophoresis and DNA polymorphism were studied systematically in this dissertation. The main results were as follows.1 Review of research advances on Fusarium (F. moniliforme)A review of research advances in Fusarium (F. moniliforme) was presented. The advances in the study on the biological characteristics (including geographical distribution, host range, morphology, biology, ecology, etc), the toxins of F. moniliforme, the vegetative compatibility and the application of molecular marker technology in the study on Fusarium are reviewed to provide a useful information for the integrated management of the diseases caused by the fungus and for the related research.2 Comparison of biological characteristics of Fusarium moniliforme isolates from different hostsMore than 200 isolates in Fusarium were isolated from the diseased tissues of cotton red rot, rice banakae disease and maize ear rot in Anhui, Shandong, Jiangsu and Hubei. According to the classification system of C. Booth and Nelson, 107 of the isolates were identified as F. moniliforme based on the morphology and culture characters. The biological characters including colony morphology, growth rates and conidium production of F. moniliforme isolates from different hosts and localities were studied by comparison. The results showed they were obviously different in colony morphology (especially in pigment production), mycelial growth rates and conidial production. The average mycelium growth rate of the isolates from cotton was the largest, next the one from rice, and the one from maize the least. There was significant difference at 0.01 levels in the mycelial growth rates among the isolates from the same population. The conidial production of the isolate from maize was the largest, next the one from rice and the one from cotton the least. The variance analysis indicated that there was significant difference in the conidial production among the isolate populations from different hosts, but no significant difference among the isolates from the same population. It was suggested that the conidial production of F. moniliforme isolates was mainly related to the host kinds, but little to the localities. The hyphae could grow in 10℃～30℃, the optimum temperature was in the range of 25℃～30℃, and the temperature lower than 5℃or higher than 40℃was not fit for the mycelial growth. The conidia spore germination was between 10～40℃, the optimum temperature was in the range of 20℃～33℃. The conidia could germinate under the condition of pH 4.1～11.8, and the optimum pH for conidial germination was about 7.0.3 Biological characters and their inheritance of Fusarium moniliformeThe isolates Fm1, Fm19, and Fm31 from cotton, maize and rice respectively were selected as tested isolates and their asexual clones of single conidia were established. The inheritance of biological characters of F. moniliforme isolates from cotton, rice and maize plants was studied in vitro. The genetic tests showed that the colony morphology and the mycelial growth rate of F. moniliforme isolates from cotton, rice and maize plants could be inherited steadily in the single conidial progenies. However, there were two exhibitions in the inheritance of the conidial production. The conidial production of F. moniliforme isolates Fm1 and Fm31, from cotton and rice respectively, could be inherited steadily in the single conidial progenies, while the character of isolate Fm19 from maize displayed variation in the first single conidium generation (CG1).4 Studies on vegetative compatibility of Fusarium moniliformeThe vegetative compatibility groups (VCGs) of Fusarium moniliforme were tested by applying the 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, maize and rice diseased tissues collected from Anhui, Shandong, Jiangsu and Hubei in China. The tested single-conidium strains were then transplanted on 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 MM medium. 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, NM and HM, the three kinds of different nitrogen media. Among the four types, nit A was the most common one, with the rate of 76%. Next were nit B and nit C, with the rates of 12% and 10% respectively. The least one was nit D, with the rate of 2%.The nit mutants then were paired on MM plates to test the vegetative compatibility of all isolates, according to their geographic location and host kinds, 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 maize 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 did isolate Fm45 from Shandong and isolate Fm16 from Anhui belong 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 that the genetic similarity among the isolates from the same locality-origin was equal to that from the same host-origin.5 Studies on the biological characters of nit mutants and the inheritance of vegetative compatibility in Fusarium moniliformeThe 240 single-conidium strains of F. moniliforme were isolated from Fm1 (from cotton), Fml9 (from maize), and Fm31 (from rice) to establish CG1 and CG2 populations. The tested single-conidium strains were then transplanted on KPS plates to mutagenize nit mutants and 1093 nitrate-nonutilizing (nit) mutants were recovered from the isolates by transferring chlorate-resistant sectors from KPS plates to MM medium. Some biological characters, such as growth rate, conidial production ability, and pathogenicity were compared between nit mutants and their parental isolates. Results showed that there were no significant differences in mycelial growth rate, conidial production ability and pathogenicity between nit mutants and their parental isolates. The genetic tests showed that the vegetative compatibility of F. moniliforme isolates from cotton, rice and maize plants could be inherited steadily in the single conidium progenies. Therefore, the nit character and vegetative compatibility can be used as genetic markers for the study of F. moniliforme. 6 Studies on differentiation of pathogenicity of Fusarium Moniliforme from different hosts to cotton and the inheritanceThe pathogenicity of the isolates of F. Moniliforme from different hosts to the leaves of cotton was investigated by applying mycelial block wound inoculation, respectively. The results showed that all of the tested isolates caused occurrence of red rot lesions on the leaves of cotton, but there was significant difference in the average diameters of the lesions caused by different isolates, suggesting that there was significant differentiation in pathogenicity of F. moniliforme to the leaves of cotton among isolates. Strongly pathogenic to the leaves of cotton, the isolated from cotton, maize and rice were weakly pathogenic to the leaves of cotton. However, there was difference in pathogenicity among the different isolates from the same host, and the pathogenicity difference was not obviously related to the localities of isolates. The pathogenicity was compared between nit mutants and their parental isolates. Results showed that there were no significant differences in pathogenicity between nit mutants and their parental isolates. The genetic tests showed that the pathogenicity of F. moniliforme isolates from cotton, rice and maize plants to cotton seeling leaves could be inherited steadily in the single conidium progenies.7 Studies on effects of culture filtrate and toxin of Fusarium moniliforme isolates on cotton growthEffects of culture filtrate of Fusarium moniliforme on growth of cotton radicles were tested. The results showed that there was obvious difference in the effect among different isolates. There were three types as follows: (1) The culture filtrate of this type of isolate(s) promoted growth of the radicles in a certain range of concentration. The weight of the radicles of the cotton seeds increased earlier and decreased later with the rise of the concentration of culture filtrate. The weight of the radicles got to the peak value when the concentration of culture filtrate was 30%～50%. The results indicated that the culture filtrate contains certain substance promoting growth. (2) The growth- promoting effect of the culture filtrate of this type was instable, but in general, the weight of the radicles increased with the rise of the concentration of culture filtrate. The weight of the radicles was the greatest when the concentration of culture filtrate was 100%. It was suggested that the culture filtrate contains also certain growth- promoting substance, of which the concentration was in the range of promoting growth. (3) The culture filtrate of this type of isolate(s) inhibited obviously growth of the radicles, suggesting the culture filtrate contains certain growth-inhibiting substance. Among the isolates tested, the culture filtrate of Fm31 isolated from rice in Anhui was the best for the promotion of plant growth, while the culture filtrate of Fm1 isolated from cotton in Anhui was the most evident for the inhibition of plant growth.The inhibition of the crude toxin of F. moniliforme agaist cotton radicle growth and the wilting effect on cotton seedlings were measured, respectively. The results showed that the crude toxin of F. moniliforme could obviously inhibit the growth of cotton radicles and caused the wilting of cotton seedlings. The wilting effect of the crude toxin was equal to the symptom of cotton red rot.8 Analysis of esterase isozymes in Fusarium moniliforme isolatesThe polyacrylamicide gel electrophoresis analysis of esterase (EST) isozymes of 10 isolates of F. morniliforme from cotton, rice and maize were carried out to compare their differences in EST isoenzyme zymogram. The results showed that EST isoenzyme patterns had the common band with Rf of 0.037, among all the tested strains. And there was greater genetic similarity among the isolates. But there was a significant difference in the patterns of EST isozyme among different strains. Based on EST isozyme and cluster analysis, those 10 strains were divided into 3 groups. There were 4 main isoenzyme bands and more minor isoenzyme bands in in EST zymogram of the strains in Group 1, which were from cotton. There were 3 main isoenzyme bands in in EST zymogram of the strains in Group 2, which were from rice. There were 2 main isoenzyme bands and a few minor isoenzyme bands in in EST zymogram of the strains in Group 3, which were from maize. It was also found that the pathogenicity difference was obviously related to esterase isozymes. Group 1 strains, cotton strain, have strong pathogenicity to cotton seedlings.9 Analysis of the dynamic activity of resistant enzymes in cotton plants inoculated with different Fusarium moniliforme isolatesThe activities of PPO, POD, and SOD in tested cotton plants inoculated with F. moniliforme isolates from different hosts were tested and analyzed in 10 days after inoculation respectively. The results indicated that PPO, POD and SOD activities in leaves all rose obviously compared to the control, which suggesting the isolates could induce the rising of the activities of the 3 enzymes in the plants by inoculating with them. Meanwhile, the activities of POD and SOD rose obviously after inoculation, while the increase of PPO activity was not significant. Therefore, PPO, POD and SOD all were related to the disease-resistance of cotton seedlings, especially POD and SOD with greater potential. The results also show that there was difference in the inducing effect of the activity of 3 enzymes among the strains from different host sources. Fm31 (rice strain) has strong ability of induction of PPO and SOD. Fm19 (maize strain) has strong ability of induction of POD. However, as an original pathogen, Fm1 (cotton strain) displayed a moderate ability of induction of the activity of 3 enzymes related to defence.10 RAPD-PCR analyses of genetic diversity in Fusarium moniliforme populationRandom amplified polymorphic DNA (RAPD) markers were used to assess genetic diversity among the strains of Fusarium moniliforme. A total of 18 strains isolated from different hosts were amplified with 8 RAPD primers. As the result, 90 RAPD fragments were obtained and 93.33 % were polymorphic found in the tested strains. 18 isolates tested were divided into 4 groups of RAPD and the genetic relationships among the strains were determined by hierarchical cluster method. Alike, RAPD markers were used to assess genetic diversity among the strains from different areas. 71 RAPD bands were obtained and 94.37 % were polymorphic in the tested strains. Eighteen strains tested were classified as 3 groups of RAPD and the genetic relationships among the strains were determined by cluster analysis. The results indicated that there was abundant genetic diversity in the population of F. moniliforme, which was consistent with the research results of biological characters, vegetative compatibility and their inheritance of the fungus. The study demonstrated that the differences in biological characters of different F. moniliforme isolates were resulted from the expression of different genotypes. The results elucidated the genetic relations among the strains and provided valuable molecular evidences for the idetifiction and classification of F. moniliforme.
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