Resistance Monitoring Of Magnaporthe Grisea To Prochloraz,screening Of Resistance Gremplasm And Chemical Control In Heilongjiang Province

Rice blast is a worldwide rice crop disease,the yield and quality of rice are affected and destroyed seriously.Heilongjiang that known as the granary of the north is an importa nt production base of commodity grain in China.Its rice cultivation area accounts for mor e than 70%of the northeast region.Since rice blast occurs at different levels every year,t he research on the disease is still the focus of attention.The use of resistant varieties and chemical pesticides is the main measure to control rice blast.In this paper,95 strains we re isolated from five major rice regions by tissue isolation method and 16 kinds of fungici des and mixed agents were tested for indoor virulence of rice blast in Heilongjiang Provin ce.The study of resistant monitoring to prochloraz,screening of resistant varieties to rice blast,and antiseptic efficacy in field controlling were carried out.It may provide a theoret ical reference for integrated control of rice blast in Heilongjiang Province.The specific rese arch results are as follows:（1）95 strains Magnaporthe grisea were isolated by tissue separation method.（2）40 main cultivated rice cultivars in Heilongjiang Province were selected and QA-1was used as the test strain,and their resistance to Magnaporthe grisea was evaluated by artificial inoculation.The results showed that the lowest average of grade in disease is Lo ngqingdao 21 at 1.40 and the highest is Longjing 46 at 6.33.The resistant varieties（R）acc ounted for 20.51%of the test materials in evaluation of resistance;The varieties of mediu m resistance（MR）accounted for 61.54%of the test materials in evaluation of resistance.The Susceptible varieties（S）accounted for 17.95%of the test materials in evaluation of r esistance.,The results showed that there were high quality resistant materials in the germpl asm resources of Heilongjiang Province.（3）16 fungicides were selected and their virulence was determined by mycelium growth rate inhibition method.The results showed that 75%oxime WG bacteria tebuconazole had the highest antibacterial activity against Magnaporthe grisea.The EC₅₀ value of 5.0223μg/m L;was followed by 25%azoxystrobin SC,20%fenoxanil SC and 12.5%epoxiconazole SC.The EC₅₀ values of 6.6617μg/m L,7.8561μg/m L and 9.1143μg/m L.（4）Azoxystrobin and tricyclazole were mixed in different proportions,and the best ratio was selected by virulence test.The results showed that different proportions of mixtures showed synergistic effect on the antibacterial activity of Magnaporthe grisea.The EC₅₀ value of 8.7960μg/m L,against Magnaporthe grisea was the highest when the ratio was 1:1,and the co-toxicity coefficient was 138.47.when the ratio was 1:3 and 1:5,the EC₅₀ values were 10.0547μg/m L and10.3438μg/m L,respectively,and the co-toxicity coefficients were 206.77 and 233.77,respectively.When the mixture ratio was 1:7 and 1:9,the synergistic effect was not ideal.（5）The sensitivity baseline of 95 strains of Magnaporthe grisea to prochloraz in Heilongjiang Province was established resistant monitoring of virulence.The results showed that the minimum sensitivity is 247.2558μg/m L,the maximum is 1416.6780μg/m L,and the sensitivity difference is 5.73 times.The frequency distribution of sensitivity showed a continuous unimodal curve,which was close to the normal distribution,therefore,the EC₅₀ average of all strains that is 613.4561μg/m L is used as the sensitive baseline of Magnaporthe grisea to prochloraz in Heilongjiang Province.The resistance level of the isolated resistant strains was 1 to 3 times,indicating that the tested strains were resistant to prochloraz.（6）The results of Experiments in field showed that the best control efficiency was the treatment of 75%oxime WG bacteria tebuconazole on leaf blast,and the control efficiency was more than 90%.Followed by the treatment of 25%azoxystrobin SC,20%fenoxanil SC and the mixed agent,but their control efficiency were all above 80%,the control efficiency of the treatment of the75%tricyclazole WP was less than 70%,which is relatively low.The effect is not ideal.