On Physiological And Biochemical Characteristics Of Fusarium Moniliforme And Screening For Effective Mixed Preparations

The effects of temperature, pH and nutriment on the mycelial growth and conidial production of Fusarium moniliforme Sheld, the causal organism of cotton red rot were studied, and the electrophoresis maps of esterase (EST) isozymes and soluble proteins of 4 isolates in F. morniliforme from cotton red rot bolls and 6 other isolates in Fusarium were analyzed by applying polyacrylamicide gel electrophoresis, and the dynamic activity of resistant enzymes such as superoxide dismutase(SOD) in the cotton plants treated with artificial inoculation of F. morniliforme were measured. Moreover, EC50 values of 7 kinds of fungicides and the co-toxicity of their mixed preparations to the pathogenic fungus were tested by means of mycelium growth rate method under the condition of laboratory, respectively, to screen the effective mixed preparations for the control of the disease .The main results were as follows. 1. The research of biological characteristics of F. moniliforme showed that the mycelium could grow at 10-35℃ , with the optimum temperature being in the range of 25-30 ℃. It couldn't grow below5℃ or above 40℃, and the lethal temperature of conidial was 52 ℃, 10 min. The mycelium could grow under the condition of pH 2.5 to 12.5, showing double peak curve, suggesting that there were two optimum pH values, 5.5 and 10.3. The conidiospore could germinate under the condition of pH 2.47～10.54, with the optimum pH for conidiospore germination being between 3.99 and 7.0. The pathogen could use many carbohydrates and nitrogen sources. For mycelial growth on solid media, the optimum carbon source was glucose, next being maltose and mannose. The optimum medium for conidial production was sucrose, next being maltose and glycerol. The more suitable carbon sources for mycelial growth in liquid medium (mycelial dry weight) were fructose and maltose. And for mycelial linear growth, the optimum nitrogen sources were (NH4)2HPO4, next being KNO3 and NH4NO3. The optimum medium for conidial production was NH4NO3, and the growth of F. moniliforme in liquid medium showed that NaNO3,as a sources of nitrogen, was optimum for mycelial growth.The better media for mycelial growth of F. moniliforme were potatoⅠ(Tomato 125 g + H2O 1000 ml + Agar 20 g)and potatoⅡ(Tomato 125 g + C6H12O6 2.5 g + H2O 1000 ml + Agar 20g)among the 11 tested media. The conidial production was different with medium kind, and it was the highest one in the soluble starch medium, then PSA, middle in potatoⅡ and PDA and very few in the other media tested. 2. The polyacrylamicide gel electrophoresis analysis of isozymes and soluble proteins of 4 isolates of F. morniliforme from cotton red rot bolls and 6 other isolates in Fusarium from the other host plants were studied to compare their differences in isoenzyme zymogram and electrophoresis map. Then hierachical clustering method was employed to analyze the results of electrophoresis. The results showed that there were clear differences in EST zymogoam and soluble protein electrophoresis map between different species and between different isolates in Fusarium, and that 10 strains were divided into three groups. It is suggested that electrophoresis technique was a useful tool in the classification of Fusarium and F. moniliforme and could be used to classify Fusarium on both specific and infraspecific ranks. 3. The activities of PPO, POD, and SOD in tested cotton plants inoculated with F. moniliforme were tested and analyzed respectively in 10 days. The results indicated that POD and SOD enzymes activities in leaves rose obviously, which suggesting they were disease-resistant enzymes of the F. moniliforme on cotton. Meanwhile, PPO enzyme activities in Zhongmian-29 rose obviously after inoculation. Though PPO activity had improved, it was not significant. The isoenzyme zymograms and electrophoresis maps of PPO and POD showed that the binds of POD, SOD isoenzymes had not increased, but apparently widened, and the color of the binds turned to deep, which suggesting that the activity had improved.The result was accordant with t...