The Research On The Resistance Of Phyllostachys Esculentum Castanea Mollissima Var.tielitou' To Different Diseases In Hunan

Castanea mollissima blight is a branch disease caused by parasitic cryptosporidium occurring in chestnut planting areas all over the world.Chestnut blight is one of the important factors restricting the healthy development of chestnut industry.In order to solve the problems of difficult identification of early symptoms of chestnut blight,difficult identification of pathogenic bacteria and few resistant varieties,this study took Hunan's main chestnut variety "Castanea mollissima var.tielitou" as the research object,carried out field investigation in its planting area,collected suspected chestnut blight branches for isolation,purification and culture of pathogenic bacteria,combined with morphological observation,physical and chemical properties determination and molecular detection technology for strain identification to obtain pathogenic bacteria.On this basis,potted plants were used to inoculate pathogenic bacteria to observe and explore potential hosts of pathogenic bacteria.In vitro water culture of branches was used to connect the isolated pathogenic bacteria back to healthy branches of "Castanea mollissima var.tielitou"from different producing areas.The occurrence symptoms of plant diseases and the main physiological and biochemical characteristics of branches during the occurrence process were recorded and measured,and the correlation between the two was analyzed to understand the occurrence regularity of the diseases.At the same time,the correlation between soil factors and incidence rate of chestnut blight in the "Castanea mollissima var.tielitou" planting area in Hunan was analyzed,and the key soil factors affecting occurrence of chestnut blight were identified.The main research results are as follows:1)"Castanea mollissima var.tielitou" in different cultivation areas in Hunan has been infected with chestnut blight to varying degrees,and its pathogenic bacteria include two strains with strong and weak virulence(F1 and F2).The nucleotide sequence homology between the two strains and chestnut blight model strains is 96%-100%,which is highly consistent.The morphological characteristics and physical and chemical properties are the same as those of the model strain,further confirming that the isolated pathogen of chestnut blight is chestnut blight.2)The pathogen has a wide host range and can infect plants such as Castanea henryi?Toxicodendron succedaneum and Carya cathayensis and cause ulcer spots.It can infect plants such as Setaria viridis?Rohdea japonica?Citrus reticulata etc.but no disease symptoms appear.3)After inoculation of F1 and F2 pathogens into branches of "Castanea mollissima var.tielitou" from different producing areas,the main biochemical characteristics in the onset process and the incidence rate after 20 days are different.The incidence of F1 and F2 strains inoculated on chestnut branches in Liuyang(LY)was the highest,with 77%and 72%respectively,showing high susceptibility,while Changsha(CS)showed strong resistance to F1 and F2.Yueyang(YY),Chenzhou(CZ)and Huaihua(HH)showed F1 resistance and showed moderate resistance to F2 strains.However,the average incidence rate of F2 strain inoculated in 5 regions is higher than that of F1 strain inoculated.4)The results of field investigation of chestnut blight are basically consistent with the results of pathogen inoculation in vitro culture of branches,LY has a high susceptibility rate and belongs to susceptible area.CS and HH are highly resistant to chestnut blight and belong to disease-resistant regions.YY and CZ are both moderately disease-resistant regions.The incidence rate of chestnut blight in different planting areas of "Castanea mollissima var.tielitou" is inversely proportional to the thickness of soil layer in the planting area.The incidence rate of chestnut blight in areas with 40-50cm soil layer thickness is higher than that in areas with 50-60cm soil layer thickness.Soil pH will also affect the occurrence of chestnut blight.The soil pH is between 2.9 and 3.2,The incidence rate is below 20%,and the mortality rate is also relatively low.The above results provide reference for early detection of chestnut blight and selection of resistant varieties,provide theoretical basis for reasonable cultivation of chestnut industry in Hunan,reduce occurrence and harm of chestnut blight,and lay a foundation for further in-depth study of its control measures.