Screening Resistant And Relative Resistant Mechanism Research To Gummy Stem Blight In Cucumis Sativus/hystrix Introgression Lines

Gummy stem blight caused by Didymella bryoniae is a serious global disease.It often causes the production cut 20%of cucumber(Cucumis sativus L.)and affects the commercial production of cucumber if illness is serious.It has important significance using the excellent genes of wild sour cucumber(Cucumis hystrix Chakr.,2 n = 24)as a background to screen the resistant material of gummy stem blight from cucumber-sour cucumber introgression lines,clear pathogenic infection process of bacteria and inquiry the associated resistance pathways in cucumber with Cucumber narrow genetic background.This paper cleared the infection process,pathological structure changes of the host tissue and the genes expression related to resistance defense signaling pathways which is through screening resistance materials to gummy stem blight from cucumber-sour cucumber introgression lines,sampling and electron microscope after inoculation by Didymella bryoniae.The main results were as follows:1.Verification of cucumis sativus/hystrix introgression lines and screening resistant to gummy stem blightAgronomical traits were observed and SSR molecular markers were analysised with cucumber-sour cucumber introgression lines and susceptible material ’Beijing Jietou’ for test.The results show that the introgression lines carry some sour cucumber morphological traits;SSR analysis indicated that the introgression lines could amplify sour cucumber specific bands which confirmed these introgression lines containing chromosomal fragments from sour cucumber.There are 995 pairs of SSR markers for parents to filter and 359 pairs of SSR markers were detected with polymorphism between the parents which the polymorphism rate was 35.8%.86 introgression lines were subjected to artificial inoculation under greenhouse condition to screen for materials resistant to gummy stem blight and 8 resistant materials(CSIL2,CSIL41,CSIL49,CSIL52,CSIL57,CSIL58,CSIL59,CSIL72)were selected from the cucumber-sour cucumber introgression lines,accounting for 9%of the tested materials.2.Ultramicroscopic investigation into the infection process of gummy stem blight(Mycosphaerella,melonis)in cucumberThe material which were CSIL72 and ’Beijing Jietou’ as resistant and susceptible for test were observed in different time by scanning electron microscopy after inoculation with artificial inoculation Mycosphaerella melonis.Hyphae distributed reticulation on the cell surface and spore Terrier growth new sporulation finally with spore germination at 8 h after inoculation,germ tube elongation,hyphae growth and branching;Directly infection of hyphae broke the skin cells and grew in intercellular and intracellular,which included appressoria formation by swollen at hyphae top,cell wall degradation by gelatinous substance from appressorium,melanin distribution around the appressorium;then the plasmolysis and chloroplasts messy arrangement appear and disintegration finally in host cell.The critical period is during 3 days after inoculation which is the recognition between bacteria and host.3.Expression analysis of major genes involved in signaling pathways during infection of cucumber with Mycosphaerella melonisThe material which were CSIL72 and ’Beijing Jietou’ as resistant and susceptible for test were observed in different time(0 h、12h、24 h、2d、3d、5d、7 d)to analyze the expression of associated genes for defense signaling pathways on ethylene,jasmonate,salicylic acid and pathogenesis-related proteins by Real-time PCR after inoculation with artificial inoculation Mycosphaerella melonis.The results show that the expressions levels of the jasmonate,salicylic acid signaling pathway related genes and pathogenesis-related protein genes(PR2,PR9)in CSIL72 were significantly higher than that of’Beijing jietou’,as well as expression amount of the ethylene defense signaling pathway-related genes in CSIL72 was significantly lower than the ’ Beijing jietou’.