On Alternaria Alternata Toxin And Mechanism Of Its Pathogenicity To Eupatorium Adenophorum

Alternaria altern仍a(Fr一 Kelssler Is a natural pathogen tocrofton weed(E叩aorium adenophorum),while th main 脉tor resulted indiseases was phytotoxln produced by the fun圳．ExPenments wereconducted to study the capability and culture conditions of toxin production,andthe purification,pathogemc range and physlolo9caf mechanism of＊theismtOXlll． Bycomparingmethods ofexclsed leaf比st,seedlingso欢lug,n的dlepuncturingand seedgemlnatlon仙lblting,needlepunct皿ngwasdetermlnedasthe malnbloass时 methods forA．alternaMtoxin．Byusingneedle punctunng,the toxin－Woducing ca帅ility of six isolates 501,503,402,LS,YN and AWAWhadhen assessd,andthe results showedthatthetoxin－producing则o劝lity of Isolate 501 was池e highest． By anaiyung the 4 tested solid media (whea,corn,soybean and rice),whet！me山M io40％ water was SS讪巾kbrkd出卜 501 to prcdoducetoxin．Thoe was not slplfic咖 di地心mc of toxin pencing cpeility ontbee h…d c咖皿 media(PSK,SCSC andand tcafjui比 ofcrofton weed)．horder to facilitate the pepa觎ion ofcuh叮e me山urn,bloassay ofascptlcmtrate and pdncation oftoxln,PSx was sebded as the m时or culturemedium for producing toxins．Exprlmental results showed that themaximum toxin production was加tamed at 25℃,pH 4．13 under static anddarkcondltlon,and the optimum on扣吐e time was 5－7 d叮s． P8thogClllC tOXlll PfodllCCd by ISO18tC 50！WSS fC18tlVC！y StsblC．PH,temperature,storagetlmedldnotbave sl队lficantlmpactonthebloactlvltles of toxin．Dxlns prduced by Isolate 50 somewhat hadhost·speclDc activity,Sonchus derace叭 Commellna communls,乙mmeljna bengalensis,Robtnia pseu加acacia,AI格rnanthera 英文嫡羹75phlloxero,血s,h吧ar,a ananassa were highly sensitive and could be usedasbloassay materlalsto isolate andevaluate the toxin． The phytotoxln to the weed from Isolate 501 was isolated and purlhedby usingabstract,column chromatography and TLC．The maximallyabsorbed Peak wavelenph of the toxin produced by Isolate 501,which waspathogenlc toE adenOPhorum,was 296urn,and the Rfwas 0．34． Thetoxln had hlghblologlcal activity．hxln at卜g／gcould causetypical leafspotdlsease．Aftertreatment for 12 hours,toxin at 5 u gig couldcause stem atrophy and leafwlltofZ－month－oldE．adenoPhorum seedling．Thetoxln Influencedonthe perme劝lllty ofcell membrane oft．adenophorum！eaves In vato,caused serious leakage of K"and Na",andIncreased MDA content of leaf tissue．Meanwhile,blobelcal actlvltles ofprotective enzymes suchas C矾 POD and APXdecreased,resulting Indisease ofE．adenoPhorum leaves． The studyofphyslologlcal mechanism oftoxlnprovedthatpathogenlcltyofA．alternatatoleaves oft．adenOPhorum hadcloserelatlonshlpwlth toxins．The research results would provldethetheoretlcalbasis ofdevelopment ofa mycoherblclde for crofton weed usingthe fingusandor卿lsm－sourceherblclde usingthetoxln．...