| False smut (green smut) of rice caused by the fungal pathogen, Ustilaginoidea Virens (Cooke.) Tak. has been reported from the most of rice-growing areas in the world. In recent years, rice false smut has become one of the most important fungal diseases of rice In China and one of the most destructive factors in food safety and rice production. On the background of rice false smut serious occurred in Sichuan province and resistance of cultivars significantly differed, these studies evaluated the resistance of rice false smut of different cultivars and screened some resistant cultivars, analyzed the genetic background of cultivars that hold different resistant and discussed the correlation between the genetic background and cultivar resistance, and studied the techniques of preventing and controlling rice false smut. The results were as follows:1. The resistant performances of 157 varieties to RFS were identified. Test result indicated that the resistance to RFS showed a great variation among the different varieties. The rate of infected rices ranged from 1.28% to 26.71%, a percentage difference of 25.43 between the highest and lowest infected varieties. Disease Index ranged from 0.43 to 18.45 with 18.02 different between the highest and the lowest. Evaluation was conducted by the rate of infected plants.15 varieties were identified as resistant varieties, while 62 as mildly resistant2. The PCR amplification for 24 important cultivars planted in Sichuan was carried out with 5 RGA primers. The cluster analysis showed that there was very low similarity in resistant genetics and great difference in genetic background among 24 sample cultivars. Under the level of 0.77 genetic similarity, these cultivars can be classified into five classes. Class I included 10 cultivars with the rate of infected plants ranging from 8.20% to 75.78%. Disease index ranged from 2.19 to 49.22. One is mildly resistant, while 3 susceptible,1 mildly susceptible, and 5 highly susceptible. Class II included 4 cultivars with the rate of infected plants 10.24%,39.81%,52.18%,75.93% and Disease Index 4.29,24.49,32.81, 52.67, respectively. One is mildly susceptible, while three are highly susceptible. Class III included 5 cultivars with the rate of infected plants ranging from 28.00% to 67.63%. Disease Index ranged from 15.38% to 45.72%. Two are susceptible, and three are highly susceptible. Class IV included 4 cultivars with the rate of infected plants 21.24%,30.41%, 33.33%,26.31% and Disease Index 6,29,18.69,13.91,29.56, respectively. One is mildly susceptible,2 are susceptible and 1 is highly susceptible. Class V included only one cultivar which was mildly susceptible with rate of infected plants 17.50% and Disease Index 9.17.3. By studying the performance of rice false smut in 4 key stages:seedling, tillering, booting and full heading, the result come that the treatment in booting stage can prevent this disease most effectively in every seeding date, exceeding 90%. It indicated that the booting stage is the key time for preventing from rice false smut.4. Four chemical agents were employed to study the optimum application frequency and stage for preventing RFS. The results indicated that the best time to application was the seventh day prior to breaking for rice. Two applications were more effective than only one.5.17 fungicides were used 7 days before crevasse and 7 days after the first treatment to control rice false smut. The tests screened a number of high pollution-free low toxicity and residue of fungicide, such as,43% Hrizon SC 15ml/667m2,30% Armure EC 15ml/667m2. Control effect of these fungicides may be more than 90%. These fungicides can be used as an effective prevention and control of false smut control agents.
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