Physilological And Genetic Differentiation Among Curvularia Species In Maize Leaf Spot

31 isolates of Curvularia lunata in maize leaf spot were isolated and identified, and 4 typical Curvularia species were used to measure and calculate their pathogenicity and parasitic fitness with representative inbreds and hybrids. The pathogenic order of 4 typical Curvularia species as following: C. lunata> C. intermedia>C. clavata>C. .eragrostidis, i.e. C. lunata had the strongest pathogenicity and is accorded with the fact of predominant species in nature. Ther were significant differences in incubation period, lesion type, lesion size and sporulation of these 4 Curvularia speices treating different inbreds and hybrids, which belonged to horizontal resistance.The inducing death of root cap cells bioassay was firstly used to measure the toxicity of toxin from Curvularia spp. The toxin from Curvularia spp. could induce electrolyte leakage of maize leaves. The amount of electrolyte leakage was highly related to the treating time and concentration of toxin. The influence of strong pathogenic isolates on resistant varieties were higher than those weak pathogenic ones. There were no marked differences among susceptible varieties while their exposuring to toxin.To some extent, the relationship existed among pathogenicity differentiation, production of toxin and isozyme polymorphism in Curvularia spp. The isozyme analysis of Curvularia spp. showed that a specific band at Rf 0.57 of esterase isozyme was relevant to pathogenicty of isolates used. Peroxidase and soluble protein as genetic polymorphic marker could be used to identification at the level of species.The optimal RAPD reaction system was established. In the total volume of 25uL, there were 5U/ L Taq DNA polymerase ,0.25 L; 2.5mMdNTP,2 L; 10 M arbitraryprimer, 2 L;10ng/ L template DNA, 5 L, Amplification was performed by the following program: 3minutes at 95 ,lminute at 36 ,2minutes at 72 ,40cycIes; a extension of 5 minutes at 72 ,and finally stored at 4 .A total of 23 primers was employed for PCR amplification of 31 Curvularia spp. Isolates. Among the 208 RAPD markers obtained, 74.5% were polymorphisms through clustering analysis, homogeneous isolates had high similarity except for Curvularia lunata, the similarity of Curvularia spp. in different isolates varied greatly.