| Sclerotinia rot is a major disease of sunflowers, which has caused great economic losses in the sunflower producing areas. It is limitation to the development of sunflower production. So this thesis conduct systematic research of Sclerotinia sclerotiorum from the following respects:the biological characteristics, genetic diversity and differentiation of pathogenicity and the physiologicaland the resistance mechanism of sunflowers. The research results will be provid the theoretical the breeding and resistance to diseases, and comprehensive prevention of sclerotinia disease. The results were obtained as follows:1. The optimum temperature for sclerotia germination is 20℃ and the most suitable relative water content for soil is 50%. After the treatment of low temperature under -5℃ and -20℃, the 20d sclerotium can be germinated 5～10d in advance, and the medium acidity is more conducive to the germination. The less deep the scleroticum is buried in the soil, the more conducive it is to the germination of sclerotia. The optimum temperature for the germination of ascospore is 25℃, the optimum pH 7～8, and PS nutrient solution has obviously promoted effect on the germination of ascospores, but the light has no apparent effect on the germination of ascospores. The optimum temperature for ascospores infection is from 20-25℃, and relative humidity is 100%.2. Application of mycelium affinity groups combined with microsatellite marking technology studied the genetic S. sclerotiorum diversity of sunflowers, and the results of mycelium affinity groups showed that 115 strains were divided into 35 MCGs,9 MCGs of which were independent affinity groups composed of single strains. It indicates that the variation of nutritious affinity groups between different strains from different areas is greater with its genetic diversity and population differentiation. The monolithic clustering result of microsatellite markers showed that the bacterial strains geographically close to each other were clustered into one group, but the distant strains were not cluster together, which indicates in the Northeast of China the sunflower S. sclerotiorum has genetic diversity.3. The pathogenicity of strains, mycelial growth rate, oxalic acid production and total acid were measured by 115 sunflower S. sclerotiorum (35 MCGs mycelial compatibility groups included) through the detached leaf inoculation method, and we analyzed the correlativity between the pathogenicity and mycelial growth rate, oxalic acid production, total acid. The results showed that the pathogenicity of S. sclerotiorum has a significant positive correlation with oxalic acid; has significant negative correlation with the total acid value; has not correlation with the growth rate of hypha.4. In order to establish the effective field inoculation method of sclerotinia disease, the researchers used the S. sclerotiorum mycelia suspension and spore as suspension the inoculums to respectively inoculate the resistant and susceptible varieties of sunflowers during the squaring period, early flowering season and full-bloom period and also compared moisture material and moisture retention time after the inoculation. The results showed that the both kinds of inoculation can make plate rot in resistance and susceptible varieties of sunflowers. Inoculated with the mycelium suspension and spore suspension, the concentrations were 10.0～15.0g/L or 1000～5000 A/mL, and inoculated during the early flower period with kraft papers moisture for 2～4d, the retantence of difference between the resistant and susceptible varieties of sunflower can be differentiated immediately. With this type of identification method,7 sunflower varieties were identified which were resistant to sclerotinia rot.5. Changes of PG, PE, chitinase, glucanase, invertase activity and MDA, soluble sugar, free proline, protein, lignin content of different resistance varieties of sunflower treated with crude toxin were determined. Above indexes significantly changed after treatment with toxin, indexes of resistant variety increased faster and higher in a more large range than susceptible variety except PG, PE, MDA. These were significantly increased in the susceptible varieties.6. After the resistant varieties of sunflower leaves were infected with S. sclerotiorum, the PAL, POD, CAT, SOD, SA, ABA, the soluble sugar, total protein and chlorogenic acid in the leaves of resistant varieties was significant higher than that of susceptible, the substances above can be used as an assistant indicator of disease resistance breeding, the PPO activity of resistant and susceptible varieties has a decreasing tendency, and the cell membrane damage of resistant varieties was slightly lower than that of the susceptible varieties, but the difference is not very notable, the MDA content in the leaves of susceptible varieties was significantly higher than that of resistant varieties, which indicates MDA was negative correlated to the resistance of sunflower to S. sclerotiorum. |
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