| Gaeumannomyces graminis (Sacc.) v. Arx & Oliver is well known as the causal agent of the take-all disease of cereals and take-all patch of turf grasses, which widely distributed in the wheat planting zone of northern China, and damages the roots of wheat and maize and become the main cause of the lose in wheat production. Although the identification and physiological characteristics in G. graminis were studied, the variation of pathogenicity, diversity of the population, and phylogenetic of the G. graminis from China have not carried out, here we conducted the works in these fields and the main results are following.We collected 63 isolates from the infecting roots of wheat in the field at Shaanxi, Gansu and Ningxia provinces, the isolates can formed perithecia on 1/2 PDA or wheat straw yeast extraction media, the characteristics of ascospores, phialospores and hyphopodia were similar to the G. graminis var. tritici isolates from Germany and Australia. However there are variation of the ascospores size among the isolates from China, these isolates can be differentiate 3 groups in the term of ascospores size, the group I is 67-74um, group II 75-82m, group III 83-89um. All isolates were inhibited in the PDA media containing 7.5% fresh oat leaves soap, and the growth rate is 0.12mm/d. Most of the isolates were increased in the PDA media containing 0.1% L-cyescine, the growth rate is 15.92mm/d. These isolates can grow in 5-30 the temperature range and 4.0-10.0 pH value, the optional temperature is 20-25, the optional pH value is 6.0-8.0.The G. graminis var. tritici isolates from China can damage the root tissue of the most cereals including wheat, sorghum, rice, Panicum miliaceum, rye and maize. Some isolates can damage oat. A total 51 isolates of G. graminis var. tritici and G. graminis var. maydis were compared for their pathogenicity on wheat and maize seedlings inoculating with mycelium disc in the glasshouse. Isolates of G. graminis var. tritici varied continuously in pathogenic adaptation to maize, from those non-attacking maize to those infecting substantially. The degree of pathogenicity of some G. graminis var. tritici isolates was higher than that of G. graminis var. maydis. The variation of the pathogenicity of these isolates was measured among the different maize cultivars.The 34 isolates of Gaeumanonmyces and Phialophora from China and Germany were analysis by random amplified polymorphic DNA (RAPD), the isolates could be formed seven groups, which is identical to the taxes classified by morphological characteristics. The isolates from China and Germany can be further subdivided into 2 groups, it showed that the relatedness of the isolates is related with the geographic distance.The 18S rRNA gene, the 5.8S rRNA gene, the 28S rRNA, and the internal transcribed spacers (ITS) of 3 isolates of G. graminis var. maydis and 8 isolates of G. graminis var. tritici from China were sequenced. The relatedness of Gaeumannomyces and Phialophora isolates from China and European were assessed by comparison of ITS sequence, G. graminis var. maydis, and G. graminis var. tritici isolates can be distinguished from each other by nucleotide sequence differences in the ITS regions. Phylogenetic analysis of the ITS regions of G. graminis var. maydis and P. zeicola, and P. radicicola suggests that the isolates are actually more closely related to each other, that the telemorph of P. zeicola and P. radicicola, if it exists, must be G. graminis var. maydis. The phylogenetic tree showsthat the G. graminis var. tritici isolate 9802 and 9735 from China were closely related to the isolate Rl, which is the rye attacking isolate of G. graminis var. tritici from England.The forward primer GgmF of G. graminis var. maydis was designed by comparison of sequences of ITS 1 regions among G. graminis var. maydis and related varieties and species of Gaeumannomyces and Phialophora. The primer GgmF and reverse primer ITS4 can amplify a 480bp products from G. graminis var. maydis but not from other varieties of G. graminis and re...
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