Studies On Indentification,Pathogenicity Differentiation And Prevention Technology Of New Disease Named Longan Pink Disease Caused By Trichothecium Roseum

Longan(Dimocarpus longana Lour)is one kind of evergreen trees,which is widely grown in subtropical zone of south China.Along with the development of longan industry,the diseases were gradually increased.A new disease was discovered in Hainan,which is endangered growth stage of longan fruit.According to the symptoms,named it pink disease.The disease has been the most important factor influence the quality and production of longan fruit.According to the new disease,the study on the basis of the investigation of the disease in the field,combine the pathogen biology and molecular biology identification to identify pathogenic bacteria.Understands the biological characters of the pathogenic.Using indoor inoculation and ISSR researched pathogenicity differentiation.According to the laboratory fungicide screening test and field control effciency,screened out two better control effect germicide to supply theory basis for scientific control in the future.The main results are as follows:1.Investigation of occurrence in the fieldThree consecutive years’ investigation of prevalence situation of longan new disease from 2013 to 2015 in field,the result showed different regions of the disease incidence and index were different.in different years.The incidence and disease index were 71.67%and 30.42 which took place in 2013 is more serious.By 6 spatial distribution patterns of aggregate indices and Iwao M*-m regression investigate longan disease.The result showed that the 1～7 plots are aggregated distribution and 8th is uniform distribution under vertical distribution during the occurrence period of longan disease.The diseased plants in all survey plots were aggregated distribution,in upside,central and lower of the horizontal direction.2.Research on Pathogen(1)Identified isolated pathogen.Isolation and purification of pathogeny from diseased fruit from the field,got 4 strians.Inoculated back the pathogeny to the longan fruit.Disease symptoms after inoculation were the same as that on the collected samples,which showed the fungus was the pathogen(Two strains isolated from the two abnormal orchard of sanya were named T3 and T4 respectivel.The strain isolated from Baoting was named T5,and the strain isolated from Lingshui was named T6.).The conidia’morphology of the pathogen were similar to that of Trichothecium roseum.Comparing the measured sequence with the related sequence in Gen Bank,the homology was 99%.The studies suggested that the pathogen causing the Longan Fruit Rot in Hainan Province was Trichothecium roseum.(2)The research about biological character of the pathogenic.The lethal temperatures of mycelia was 54 ℃、10min,the lethal temperatures of conidia was 52 ℃、10min,the mycelium could grow under the condition of pH 3 to 12 and the optimum pH values for mycelium growth between 4 to 6.The best carbon souces are mannitol and glucose,the best nitrogen sources for mycelium growth are sodium nitrate and potassium nitrate.Under different illumination conditions,different strains are different.Among them,the growth rate of strain T1,T3,T4,T5 was the fastest in all dark conditions.And the growth rate of strain T2 and T6 was the fastest under the condition of full light irradiation(The T1 and T2 strains were gived from Environment and Plant Protection Institute,T3、T4 and T5 are separated and purified by our project team).(3)Pathogenicity study.There was significant differentiation in pathogenicity of 6 Trichothecium roseum strains.According to average disease indices of lesions on longan,the pathogenicity of all isolates was classified into four categorise:strong,mediate,weak and weaker.Inoculate the pathogen on the surfaces of banana,mango,papaya,carambola,pitaya,sugar cane,green orange and other common tropical fruit.It is found that there were differences in pathogenicity among them.The distribution of the pathogenic type of Trichothecium roseum isolates was related to theri localities.Utilize ISSR molecular markers for genetic diversity of 6 Trichothecium roseum strains.Among the 6 Trichothecium roseum strains,8 ISSR primers produced 91 loci,of which 69 were polymorphisms.and the percentage of polymorphic loci was 75.82%.The average value of number of alleles was 1.76,and the effective number of alleles was 1.48.Nei’s genetic diversity and Shannon’s information index was 0.28 and 0.41.The similarity coefficient between the 6 Trichothecium roseum strains ranged from 0.62 to 0.86.On the basis of ISSR molecular marker data,set up the cluster analysis chart.The 6 Trichothecium roseum strains were divided into two categories at the similarity coefficient of 0.62 according to different sources.3.Screening of ChemicalsPochlora had the better control effect significantly than others among the 4 testing fungicides.The second is tebuconazole.Different fungicides with time rolled EC50 also changed accordingly.The field trail results were as follows:all the control effect to longan new disease was significantly.Tebuconazole and prochloraz had preferable control effect.The control effects were 80.38%and 68.65%.