| The Rice Blast disease, caused by the ascomycete fungal pathogen Pyricularia oryzae, is one of the most devastating diseases of rice. It has happened not only in Liaoning province, but also in the whole country. In this study, the relationship between genetic lineages and pathotypes of P. oryzae, the sensitivitie to tebuconazole, SYP-7017, boscalid and cyprodinil and the resistance to tebuconazole were texted, and the main result is below.1. In order to reveal the relationship between genetic lineages and pathotypes of Pyricularia oryzae, the 93 isolates of P. oryzae from 8 rice production areas of Liaoning Province were assessed for DNA polymorphism by the rep-PCR technique. The 3～14 DNA bands among 0.4 kb～23 kb for each isolate were amplified and the results showed that the vast majority of DNA bands were between 2 kb to 5 kb. The 93 isolates were classified into 17 genetic lineages at a genetic similarity of 0.75 in clustering analysis of outweighed pair-group method by arithmetic average (UPGMA). The 1,4 and 11 were the predominant lineages, including 13,15 and 27 isolates and accounting for 13.98%,16.13% and 27.96% respectively of the total. The results indicated that genetic structure of P. oryzae population in Liaoning Province tends to be multiplicity and complexity. All of isolates were identified by 7 identified rice varieties. The 93 isolates were divided into 6 groups and 27 races. ZA and ZB were the dominant groups. ZA1 and ZB1 were the major races. The results also showed the genetic lineages of P. oryzae population were not obviously correlated with the pathotypes in Liaoning province. The same lineage can be composed of several different physiological races and the same physiological race can belong to different lineages. The relationship between genetic lineages and pathotypes of P. oryzae in Liaoning Province was complicated. It was found that there is no certain corresponding relationship between genetic lineages and pathotypes.2. The sensitivities of 109 Pyricularia oryzae isolates from 8 areas in Liaoning Province to tebuconazole were determined mycelium growth rate method. The results showed that the EC50 of the strains to tebuconazole ranged from 0.0675～1.2486 μg/mL with a difference of more than 18 times. According to Gaussian distribution of 109 strains, the average EC50 value (0.3833±0.0263) μg/mL was the baseline-sensitivity of P. oryzae to tebuconazole in Liaoning Province. No resistant strain was detected in the field. The sensitivity of strains belonging to different physiologic race groups and different areas to tebuconazole had no significant difference.3. We determine the concentration of SHAM for 80 μg/mL on the basis of the mycelial growth rate and sensitive of p.oryzae on various mediums.109 strains of p.oryzae were isolated from 8 areas in Liaoning Province,and their sensitivity to SYP-7017 were examined by mycelium growth rate method. The results showed that the EC50 value of the most sensitive strain was 0.0496 μg/mL and the EC50 value of the least sensitive strain was 1.0867 μg/mL which indicated a difference of 22 times. According to Gaussian distribution theory of wildly sensitive strains from field,the average EC50 value 0.3010±0.0207 μg/mL was the baseline-sensitivity of p.oryzae to SYP-7017 in Liaoning Province. The sensitivity of strains belonging to different physiologic race groups and different areas to SYP-7017 had no significant difference.4. We choosed minimal medium and carrot medium to determine the sensitive of P. oryzae to boscalid and cyprodinil on the basis of the mycelial growth rate, sensitive and control efficiency of p.oryzae on various media.109 strains of P. oryzae were isolated from 8 areas in Liaoning Province,and their sensitivity to boscalid and cyprodinil were examined by mycelium growth rate method. The results showed that the EC50 value to boscalid of the most sensitive strain was 0.064 μg/mL and the EC50 value of the least sensitive strain was 1.596 μg/mL which indicated a difference of 24 times and the EC50 value to cyprodinil of the most sensitive strain was 0.481 μg/mL and the EC50 value of the least sensitive strain was 8.311 μg/mL which indicated a difference of 17 times. According to Gaussian distribution theory of wildly sensitive strains from field, the average EC50 value 0.4735±0.0194 μg/mL was the baseline-sensitivity of P. oryzae to boscalid and the average EC50 value 3.9342±0.1485 μg/mL μg/mL was the baseline-sensitivity of P. oryzae to cyprodinil in Liaoning Province. The sensitivity of strains belonging to different physiologic race groups and different areas to boscalid and cyprodinil had no significant difference.5.6 resistant mutants to tebuconazole acquired by UV mutagenesis and fungicide adaptation test were used to clarify the biological characteristics, multidrug-resistance and cross-resistance. The resistance levels of 6 resistant mutants obtained by UV mutagenesis ranged from 6.5-19.2 fold. The conidial production, the growth rate and the weight of mycelium of the resistant mutants was significantly lower than that of the parent isolates. The virulence of 6 resistants had changed. The resistance of all mutants could not be inherited stably. There were no cross-resisitance between tebuconazole and epoxiconazole, difenoconazole, prochloraz and hexaconazole. No multidrug-resistance existed between tebuconazole and SYP-7017, azoxystrobin, kresoxim-methyl, carbendazim, isoprothiolane, propiconazole and difenoconazole. The resistant mutants and their parental isolates were assessed for DNA polymorphism by the rep-PCR technique. There were no difference between resistant mutants and their parental isolates. The resistant were not caused by the change of genetic lineages. |
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