On The Pathogencity And Toxin Production Of Curvularia Spp. Isolated From Corn

Maize Curvularia leaf spot was listed as a quarantine disease in Sichuan. To learn the pathogenic mechanism of Curvularia spp.on maize, the experiment has studied on the producing conditions and abilities and the pathogenic mechanism of toxin produced by Maize Curvularia spp. in Sichuan . The results shows as the follow:l.The effects of media,temperature,initial pH and time on toxin production by C.lnnata were studied. The best media was Fries3 and the maximum toxin production occured 10 ~ 1 Sdays after cultivaton, at pH3.5 and 20 ~ 25 temperature.2.The pathogenicity and the producing toxin ability of six Curvularia species and five isolates ofC.lunata were tested. The pathogencity of the different species could be be put in order: 1%(C.lunatd) > Chuanl3(C.pallescens) > M\y\2A(C.ovoidea)> SantaillB(C/wmtfa var.aeria) > Rice2 (C. senegalensis)> Rice3-l(C.c/avota). But the order of the producing toxin ablities was: Chuanl3, Rice3-l > Rice2 > Miyi2A > SantaillB >28.So there is no relationship between the pathogenicity and the producing toxin ablities of the five isolates. And the pathogenicity of five isolates of C. lunata could be be put in order: Caolv>Yaan> 6248>33>Riceye,and the ablities of producing toxin was the same as the pathogenicity.So there exists consistency between the pathogenicity and the producing toxin ablities of the six isolates.3. The toxin can damage the plasma membrane of leaves of maize. With the times diluted culture filtrate increasing, the electronic conductivities was dropping. Nevertheless the susceptible cultivar had the heavier damage than the resistant one. The toxin changed cell's ultrastructure of maize leaf, including dilated, disorganized and vacuolated granalamellae,and high density electron deposition located on the chloroplast membrane. The chloroplast, nuclear and cell collapse successively. The damage of chloroplast occured earliest and seriously. The effect of toxin on ultrastructure was heavier and faster on susceptible cultivar than on resistant cultivar.