Identification Of Pathogens Of Rice Spikelet Rot Disease And Evaluation Of Resistance Of Rice 30 Pi-genes To The Magnaporthe Oryaze In Jiangxi Province

In recent years,rice spikelet rot disease and neck blast are two extremely important diseases in mid-late period of rice development in Jiangxi province.Spike rot occurred all around the country,and also occurred heavily in Jiangxi area in recent years,especially in Jitai basin.However,few studies were reported about it in Jiangxi area.Planting of resistant varieties and using of resistance genes of varieties have always been the most economical and effective method to control rice blast.However,there are interactions between rice varieties and the physiological races of blast fungus.Therefore,understanding of the dynamic changes of the physiological races and resistance genes of rice varieties in Jiangxi area will provide an important theoretical basis for the rational distribution of rice resistant varieties and the comprehensive control of rice blast.In this study,the samples of spikelet rot were collected,4 kinds of pathogenic bacteria were isolated by morphological and molecular biological identification,and their biological status were determined.The biological characteristics of pathogenic bacteria and the pathogenicity difference between different periods and different inoculation ways were studied.Experiments on efficacy control of rice spikelet rot were carried out.For rice blast,we use indoor strains to test the sensitivity of both of the main rice varieties in Jiangxi area and the rice varieties selected by Jiangxi Academy of Agricultural Sciences.The main research contents and results are as follows:1.Identification of pathogens of rice spikelet rot disease.After a comprehensive analysis of colonies shape and morphological characters,molecular biological characteristics,and pathogenicity determination,four pathogens were identified and determined.They are Fusarium chlamydosporum,Alternaria tenuissima,Curvularia cymbopogonis and Nigrospora orizye.2.Biological characteristics of rice spikelet rot pathogens.Fusarium chlamydosporum,Curvularia cymbopogonis,Alternaria tenuissima and Nigrospora orizye were identified to be the pathogens of rice spikelet rot.The four pathogens can survive under 12 ℃ to 30 ℃.They grow well under 24 ℃ to 28 ℃.In study of different p H values,they can survive under p H4-9.Fusarium chlamydosporum grows well under p H 7.And it is sensitive to acid environment and grows slowly under p H4-5.The other three pathogens grow well under p H7-9.In study of different sources of carbon and nitrogen,results suggested there was no difference in growth and development of mycelium under different sources of carbon and nitrogen.The four pathogens can grow in PDA/Czapek–Dox medium.They grow the best in nitrogen sources of potassium nitrate medium.And they grow the best in carbon sources of glucose and starch medium.3.Pathogenicity of spikelet rot.All the four pathogens can cause the spike of rice by artificial inoculation.The pathogenic rate of inoculation was larger at heading stage than booting stage and it was larger by injecting than spraying.The pathogenic rate of Fusarium chlamydosporum was the strongest,followed by Curvularia cymbopogonis,Alternaria tenuissima,and Nigrospora orizye.4.The efficacy trials of rice spike rot and evaluation.The trials were conducted for three times,that is,before rice transplanting,end of tillering stage,and rupturing stage.The control effect: treatment of 40% difenoconazole and 70% thiophanate-methyl are the best,with control effect of 81.09% and 80.22%,respectively.5.Pathogenicity of rice blast.After detection of 85 separated monospora isolates and 7 traditional hosts,four small populations including 20 races were obtained,that is,ZA,ZB,ZC and ZE.Among them,ZA population accounted for 58.82%,ZB group accounted for 32.94%,ZC group accounted for 7.06% and ZE group accounted for 1.18%.The dominant races were ZA15(22.35%),ZA13(21.18%),ZB15(20%),ZB13(4.71%)and ZC15(4.71%).The frequency of toxicity of 85 monospora isolates against 30 single gene resistant varieties ranged from 30% to 83.33%,and the average toxicity frequency was 54.70%.6.The resistance identification of rice blast.Thirty single gene plague strains in the rice blast nursery of Jinggangshan were identified over two years.The resistance level of these strains against neck blast varied.Pi-zt and Pi-sh(2)showed moderate or higher resistance level to leaf panicle blast.