| Helminthosporioid fungi are the organisms having multi-transseptated and helminthous shaped conidia, which include 6 genera, i.e. Helminthosporium, Drechslera, Bipolaris, Exserohilum, Curvularia and Marielliottia. Most members of this group are very common plant pathogens of economic crops. Some species can cause human disease. While others of them are saprophytic on deadwood. So there is economic and ecological importance to study the helminthosporioid fungi. This study is mainly about the taxonomic research of Helminthosporium Link and Curvularia Boedijn in China. During the investigations of Helminthosporium Link and Curvularia Boedijn in China from 2001 to 2003, we had collected more than 2000 specimens from more than 20 provinces. Plus another 3000 herbarium specimens in HSAUP, we checked a sum of 5000 specimens; from which about 500 isolates were received. We discovered quite a few new and noteworthy taxa and achieved many valuable results based on the careful identification. 52 taxa at species level are described and illustrated. Among them, there are 23 new species, 1 new name, 12 Chinese newly recorded species(see addendum I)and 15 reported species from China. It is honor for us to be awarded financial support from the National Natural Science Foundation of China (NSFC) ensuring the project all right. Besides the new species, new record species discovered, some more extensive habitats and distributions for this fungus group were found. The culture media, culture condition, along with conidial septa, conidial germination, sporulation pattern of some species are studied. As a result, some useful taxonomic methods, criteria and our viewpoints concerning the two genera were concluded: Helminthosporium Link The morphology of these fungi on the natural substrates should be main identifying bases, culture features are essential and helpful supplements. Stromata are presence or not, and the size of stromata on the natural substrates are different among species, which can be one of taxonomic criteria of Helminthosporium. The characters of the conidiophores are the important identifical criteria, which include the shape(cylindrical, conic or subconic), the size, the colour and the ornament of the wall. The morphology of the conidia is the main identifical base at species level, which include the characters of shape, size, colour and ornament of the wall, catenate, rostra or pseudorostra, helium and distosepta. Curvularia Boedijn The morphology of the conidia is the main identifical base at species of Curvularia Boedijn, which include the characters of shape, size, colour, ornament of the wall, catenate, helium and septa. The conidiophores between the groups are different, but they are simlar among the species in same group. Stromata are presence or not, branched or simple and the size of stromata are different among some species, which can be one of taxonomic criteria at species level. Based on the morphological identification, in order to further elucidate relationships among the similar species and the difficulty species of maculans group of Curvularia, 23 strains were analyzed with 15 random amplified polymorphic DNA (RAPD) primers. The results show that the RAPD analysis is a very useful tool to study genetic variations of Curvularia species; the similar species and the difficulty species were clustered into different groups, they can be separated clearly by the RAPD data, this proved the correction of the morphological identification and the difficulty species(CU612) is a new taxa; there was a large variaty among C. eragrostidis and C. intermedia isolates; S151can be the specific primer to identified C. intermedia isolates. From the investigation of mitosporic fungi pathogens of 40 main weeds in north 15 provinces, we got 150 strains. Based on the careful identification, we discovered 12 genera, 47 species. Among them, there are 18 new species, 3 chinese newly recorded genera, 2 Chinese newly recorded species(see addendum II)and 27 reported species from China. 20 species have been proved... |
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