| Wheat head blight (wheat scab) caused by Gibberella zeae(Schw.)Petch is one of the most serious diseases of wheat in various parts of China. Fusarium head blight (FEB) of wheat has been linked to at least 20 causal organisms, most records of the diseases being associated with five species: Fusarium culmorum, F.avenaceum, F.graminearum, F.poue. F.nivale. In recent years, many works have been done in identification of wheat scab and screen of resistant wheat cultivars. In this experiment, 39 single-spore isolates of Fusarium spp. were collected from Hubei, Henan, Jiangsu provinces et al. in China. These isolates belong to 14 species including F.moniliforme, F.oxysporum, F.graminearum, Fcamptoceras, F.tricinctum, F.semitectum, F.annulatum, F.acuminatum, F.avenaceum, F.nivale, F.poae, F.proliferatum, F.scirpi, F.ventricosum. The variation of pathogenicity of these species was tested by artificial inoculation in budding and flowering stages using conidiospores and analyzed by SAS. The variation of cultural characteristics of Fusarium spp. was observed in PDA and compared with the differentiation of virulence. Randomly amplified polymorphic DNA (RAPD) markers were used to evaluate the genetic diversity among 39 isolates of Fusarium spp.. The results include:1. The test of pathogenicity of isolates which do not belong to F.graminearum showed that three species were highly virulent isolates, six species were intermediate virulent and the others were low virulent isolates. There was a significant difference in virulence of isolates and in resistance response of the wheat cultivars. Isolates of F.graminearum were also highly virulent. Isolates from different localites and different hosts were also different in virulence. Even isolates from the same regions and the same hosts varied significantly in their virulence. Both methods of inoculation in budding and flowering stage can idendicate the differentiation of the virulence of the causal oganisms and can be used to study the connection of isolates and wheat cultivars. Therefore, it is possible to identify disease ressistance of varieties in budding stage. It can be used as a reliable and advantageous method.2. There was a marked difference in cultural characteristics. The isolates from thesame regions and the same hosts were also different in cultural characteristics, and the differentiation appeared to correlate the pathogenicity: the growth rate of mycelia correlated directly with pathogenicity: isolates which can grow fast in PDA have high virulent. The sporulation and mycelium growth did not correlate with pathogenicity. So maybe the cultural characteristics and virulence share common genetic background or the virulence of isolates correlates genetically with biologic characteristics.3. Genetic relationships among the isolates were determined by hierarchical cluster method, and showed that there was high polymorphic among 39 isolates. Tree diagram divided these isolates into nine groups. Isolates of F.moniliforme which come from crops except wheat can be differentiated from those from wheat. And most of high and low virulent isolates can be differentiated here. Isolates of F.oxysporum can be differentiated by their orignation. But for all isolates RAPD analysis can not provide reliable molecular evidences of determining classification position to Fusarium spp. in this experiment. |
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