Pathogenicities Of Fusarium Graminearum Schw. And Its Filial Generation

357 single-spore isolates were obtained from more than 600 scabby wheat ear, which were collected from 37 locations of Hubei, Hunan, Jiangxi, Zhejiang, Anhui, Heilongjiang, Henan, Jiangsu, Shanxi,Sichuan,Hebei provinces in China during 1997-2001. These isolates were identified and classified into five Fusarium species. 344 isolates of Fusarium graminearum Schw., 5 isolates of F.camptoceras, 4 isolates of F.semitectem, 3 isolates of F.tricinctum and 1 isolate of F.culmorum were identified. Fusarium graminearum is prevailing in the fields.123 isolates different from sources and cultural characteristics were applied to identification of field pathogenicity. Three wheat cultivars, including Sumai3(HR),yangmai158(MR) and Annong8455(S), were inoculated with the conidia produced in liquid CMC medium by drip spore-suspension method during flowering stage respectively. Pathogenicities of different isolates on different cultivars reach significant difference (P=0.0001). The expansion speed of isolates on wheat had markedly correlation with their pathogenicities(P=0.0029). But the matrix colour, the growth of mycelia ,sporulation had no correlation with the pathogenicities.On basis of source, cultural characteristics, PCR analysis and pathogenicity identification, isolate XZ-01 with highly pathogenecity to wheat and 500bp unique PCR band, was paired with isolate LY-01,137,SL-05 with weak pathogenicities to wheat and 450bp unique band, respectively. The successful single ascospore cross between XZ-01 and LY-01 resulted in 3 cross-isolates ,2 between XZ-01 and SL-05, 0 between XZ-01 and 137.95 ascospores were randomly screened from isolate 34(4),a filial generation of XZ-01 & SL-05. The susceptible cultivar Annong8455 were inoculated with the corresponding conidia produced from colonies of 95 ascospores .The result showed that the pathogenicities of 44 isolates were the same as that of XZ-01, and the other 44 isolates were the same as SL-05. Seven isolates showed high pathogenicities which were different from their parents. The segregations rate of pathogenecity is 44:44:7.