The Biological Characteristics, Pesticide Screening And Variety Resistance Analysis Of Rice Aspergillus

Rice false smut is a fungal disease of rice panicle caused by?Ustilaginoidea virens?.In recent years,rice false smut has become one of the main diseases in rice producing areas all over the world.With the speed up of rice variety renewal,frequent transportation and fertilization,rice false smut is becoming more and more serious.Therefore,the biological characteristics of pathogenic bacteria were studied in this experiment,and the high efficiency and low toxicity agents were screened,and the resistance differences of varieties were analyzed in order to provide some suggestions for the control of rice false smut in the field.In this experiment,the diseased plants of rice false smut collected from Heilongjiang rice region were isolated by tissue separation method.The morphology of the pathogen was observed under microscope,and the pathogen was identified by homologous alignment of ITS nucleic acid sequences.The optimum growth conditions of Ustilaginoidea virens pathogen were determined by measuring the growth rate of pathogenic bacteria under different culture conditions,the high efficiency and low toxicity agents were screened by the growth rate method,and the resistance of rice varieties was analyzed and evaluated by artificial inoculation.The main contents and results of the study are as follows:1.The morphological characteristics of colony,hypha and chlamydospore of Ustilaginoidea virens were observed by optical microscope.After culture for 25 days,the diameter of the colony was 6.0 cm,yellow-green,the center was raised,the surface was uneven,the back of the colony was dark brown,the outer edge of the colony was light yellow,and the color gradually deepened to black with the prolongation of the culture time.Hyphal velvety and white,chlamydospore yellow,globose,surface spinous protuberance.Morphological Identification of Ustilaginoidea virens.2.ITS nucleic acid sequence homology alignment method was used for molecular identification.Primers ITS1 and ITS4 were used to amplify the DNA of the pathogen.The ITS region sequence of the pathogen was 98%similar to the Villosiclava virens sequence of Ustilaginoidea virens in Genbank.The phylogenetic tree showed that the highest homology with the ITS nucleic acid sequence?BYJ?of the pathogen to be identified was the Villosiclava virens.So it can be concluded that the result of molecular identification is Ustilaginoidea virens.3.The effects of temperature,light,pH,carbon source and nitrogen source on mycelium growth and colony morphology were studied.The results showed that the optimum growth conditions for Ustilaginoidea virens were dark,pH 6,temperature 28?,carbon and nitrogen sources sucrose and peptone,respectively.4.The sensitivity of 19 agents to Ustilaginoidea virens was determined by colony growth rate method,and the bacteriostatic effect was determined.The results showed that seven fungicides,75%oximoxime tebuconazole,75%mancozeb,25%pyrimidine,32.5%benzoyl ester,50%ethers,had good antibacterial activity against Ustilaginoidea virens,and they were75%oximoxime tebuconazole,75%mancozeb,25%pyrimidine,and 50%ethers.The EC₅₀values of 10%phenylether cyclazole,12.5%enazolol and EC50 were all less than 5.0?g/mL.Among them,75%mancozeb had the best inhibitory effect on rice aspergillosis,EC ₅₀ was 0.57?g/mL.With the worst bacteriostatic effect.The fungicide was 20%tricyclozole and its EC50value was more than 1000?g/mL.5.Ten main rice varieties in Heilongjiang Province were inoculated artificially with Ustilaginoidea virens by pot experiment.The results showed that two varieties with high resistance to?HR?accounted for 20%of the tested rice varieties.Six varieties with resistance to?R?were found to be resistant to rice false smut,accounting for 60%of the tested rice varieties,and one rice variety with medium resistance to?MR?was one,accounting for 10%of the tested rice varieties.There were 1 variety with medium susceptible?MS?to rice false smut,which accounted for 10%of the tested rice varieties.