| Rice sheath blight is one of the important rice diseases worldwide. The disease constraints rice yield seriously. Cultivating resistant cultivars is one of effective measures to control plant disease.The cultivar with high resistance to rice sheath blight was not found till now, because the pathogen is high saprophytic, wide range of host and complicated genetic background.To clarify the genetic differentiation of Rhizoctonia solani AG-1-IA, the impact factors on somatic compatibility differentiation of a virulence strain of cx-2 were studied in this dissertation basis on the investigation on somatic compatibility differentiation of the pathogen in field. The techologies AFLP was used to compare the genetic traits between the original strain cx-2 and the strains of somatic compatibility differentiation. The machanism of incompatibility between two incompatible strains was also primary studied. The main results were summarized as follows.1. The somatic incompatibility among the strains recovered from the same peddy field with a high propotion. The propotion of somatic incompatibility among the strains was continuously surveyed at the stage of 50 days after rice planting in 2012,2013 and 2014. The somatic incompatibility among the strains recovered from the same peddy field with a high propotion of 24.26% in 2012,39.22% in 2013 and 41.10% in 2014, respectively.2. Somatic compatibility differentiation of R. solani associated with rice-pathogen interaction and pH. But it was irrelevant to resistence of rice, fungcides and temperatures. Thirty rice varieties were continuously inoculated with the original R. solani strain cx-2 five times. Four hundred and fifty strains were obtained. Among 450 strains,24 strains which isolated from 15 rice varieties were incompatible with the original strain cx-2. Meanwhile,5 rice varieties with different resistance to sheath blight were also inoculated with strain cx-2. The result of the test showed that the somatic compatibility differentiation was irrelevant to the resistance of rice. Strain cx-2 was continuously inoculated on PDA plate with three fungicides (thiophanate-methyl, difenoconazole, propiconazole) 10 times respectively. The results showed that the somatic incompatible strain did not be detected. The somatic compatibility differentiation of the strain was also not found under different temperatures (5,10,15,20,25,30,35 and 40℃) after inoculating in PDA ten times.The somatic compatibility differentiation of strain cx-2 was found in PDA with pH 10 and pH11.The nutrient of medium was effected on the somatic compatibility differentiation of strain cx-2. The mediums of NA and DP could induce the somatic compatibility differentiation of strain cx-2. Peptone in the mediums of NA and DP was the major factor which induced somatic compatibility differentiation of strain cx-2. The PA medium with pH10 was the best medium to induce somatic compatibility differentiation of strain cx-2.3. The strains with somatic compatibility and somatic incompatibility showed the same pathogenicity and AFLP fingerprint patterns with their original strain (cx-2). It implied that the somatic compatibility differentiation of the strains was irrelevant to their virulence differentiation and mutation(s) in nuclear DNA.4. Under the microscope, dead anastomosis cells were observed in the juction between somatic compatibility differentiation strain and original strain cx-2, while the anastomosis cells of two compatible strains grew continuely. The formation of barrage zone in the juction of two incompatible strains was not relevant to ectocrine of strain. The signature DNAladder of cell program death was not detected in the barrage zone between two incompatible strains.The protein fingerprints were different between somatic compatibility differentiation strain and original strain cx-2 by the analysis with two-dimensional electrophoresis. Thirty nine differentially expressed protein spots were found between strain cx-2 and some somatic compatibility differentiation strain (strain 8-5). Six protein spots were detected in the co-cultureed mycelium of strain 8-5 and strain cx-2, which were different to the strain 8-5 and strain cx-2 in expressing leves respectively. |
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