Relationship Between Immune Response And Disease Resistance Of Cotton Induced By Verticillin Dahliae

Verticillium wilt is a kind of soil-borne vascular disease.The host of the pathogen Verticilliunz dahliae Kleb.is very widespread.It causes great losses to cotton production in China.The cultivation and selection of disease-resistant varieties is one of the effective ways to control Verticillium dahliae,but the lack of resistance cultivaris makes the breeding progress slowly.In order to study the mechanism of resistance to Verticillium wilt in different cotton and to reveal the similitude on infection processes in cotton roots infected by Verticillium dahliae transformants which tagged by GFP were studied.The resesrch results of the relationship between the immune response and disease resistance of cotton on cytology and molecular level studies,to provides the theoretical basis for breeding resistant varieties and separating effective antibacterial substances.The main contents and results of this study were as follows:1.Verticillium dahliae infecting different resistant cotton of corresponding defense responseThe seedlings of 14 different cotton cultivars were inoculated with Verticillizm dahliae by the irrigation root inoculation method to investigate the incidence of cotton after 6 weeks.On the basis of phenotype,disease index and AUDPC(area under the disease progress curve),14 accessions were grouped into resistance,middle resistance and susceptibility.The differences in defense responses in 14 different resistant cotton infected with 1070-2 were studied.After different resistant cotton were inoculated with Verticillium dahlia.The activities of root lignin,leaf tannins and hydrogen peroxide,and polyphenol oxidase(PPO),peroxidase(POD),phenylalanine ammonia lyase(PAL),catalase(CAT),Chitinases(CHI)and Glucanases(GLU)in leaves increased to varying degrees.The amount of increase is positively correlated with the degree of resistance.2.The infection processes in different resistance cotton inoculated by Verticillium dahliae 1070-2We observed the infection processes in resistance cotton zhongzhimian 2,middle resistance lumanyan 28 and susceptibility cotton jimian11 inoculated by Verticillium dahliae 1070-2.Before infection,conidia can be randomly adsorbed on the conidia can be randomly adsorbed on the root surfaces of three cotton eultivars.However,we found that the number of conidium on the roots of zhongzhimian 2 was less than that of lumianyan 28 and jimianll.Moreover,the germination,time and rate of spores of zhongzhimian 2 was less than that of lumianyan 28 and jimian11.During infection process,7 days after inculation,in the internal vascular tissue of iimian 11,the filaments are intertwined and grow along the longitudinal axis of the root and extend in the gap between the vascular tissue cells.9 days after inculation,only part of hyphae in the internal vascular tissue of lumianyan 28 expanded.11 days after inculation,this phenomenon was observed in the vascular tissues of the zhongmian 2 and only some of the catheters had fluorescent mycelium.When the symptoms were formed,the stems of jimian 11 were browned and the leaves were wilting and chlorotic,and a large number of mycelium of Verticillium dahiae were observed on the diseased leave.Milder symptoms of lumianyan 28 was observed and fewer diseased leaves on the plants.Among the resistant cotton zhongzhimian 2,the mildest symptoms of Verticillium wilt and only a few mycelium were present on the leaves.3.Separation of resistance substances from cotton against Verticillium dahliaeThe resistance substances from three different cotton were extracted by cold leaching.In flat panel testing experiments,the tissue extract of Zhongzhimian 2 after inoculation with Verticillium dahliae showed strong antibacterial activity.The antimicrobial substances of Zhongzhimian 2 reduced the number of spores of VD1070,damaged cell membranes and released large amounts of intracellular substances.However,the tissue extracts of the inoculated and untreated jimian11 did not inhibit growth of Verticillium dahliae.4.Cloning of Verticillium dahliae chitin synthetase geneVerticillium dahliaechitin synthetase gene(CS)were found from NCBI gene library,and PCR primer were design,four genes were cloned from Verticillium dahliae V1070.The gene of Verticillium dahliae may be the new type of chitin synthetase gene family;chitin synthetase have the relationship with Verticillium dahliae induced immune response in cotton which were inoculated three strains by root irrigation method.