Studies On The Interaction Between Wheat And Fusarium Graminearum

Fusarium head blight or wheat scab, caused by Fusarium graminearwn (Teleomorph Gibberella zeae (Schew) Petch), has been the most important disease of the southern winter wheat and northeastern spring wheat planting areas in China. In the middle and lower valley of Yangtze River, wheat scab often broke out severeely and caused severee yield loss and grain contamination with Fu.sarium toxins. It was estimated that wheat scab affected more than 6.7 million ha in China. This paper focuses on the interaction between wheat and Fusarium gram inearwn.Screening techniques of wheat resistance were evaluated including injection inoculation with conidia suspension, spreading inoculated grains in the field and toxin bioassay. Wheat resistance could be identified from the symptoms of inoculated spikes. On highly resistant varieties, the symptoms were restricted to the inoculated spikelct. In susceptible varieties, severee symptoms spread to the rachis or whole spike and caused head wilt. The appearance of moderately resistant varieties was intermediate; the disease developed along the rachis and the spikelets adjacent to the inoculated floret. Therefore, the scab resistance of varieties was most reliably determined by injection inoculation. This method could be quickly and reliably used for evaluating the spread resistance of the key materials and advanced lines, and even for the genetic study of scab resistance. The etiolated coleoptile bioassay was used to determine the resistance to Fusarium toxins. However the result by the etiolated coleoptile bioassay was consistent with the result from the injection inoculation. This suggest that resistance to disease spread be associated with resistance to Fusarium toxin or detoxification.Pathogenicity was tested of 160 isolates of Fusariwn graminearum collected from iiangsu, Shanghai, Anhui and Fujian province in 1998 on three varieties with the conidium suspension injection inoculation in the greenhouse. In Sumai 3(R), Yangmai I 58(MR-MS) and Ningmai1扟?986(S), the disease grade average was 1.92, 3.38 and 3.84 respectively, suggesting that Fusarium graminearum had strongest pathogenicity on the susceptible variety.The isolates can be divided into 5 types according to conidium production potentiality.Strong, middle and weak conidium-production types, no spores-production type and no typical conidium but microspore production type. Pathogenicity of last 3 types of isolates was weaker than that of the first 2 types of isolates. But Conidium production potentiality did not determined the pathogenicity of isolates. Some no conidium isolates had middle strong pathogenicity. To date, no pathogenic specificity of isolates of F gramineczrum has been found.The isolates, which produced high potentiality of DON, had stronger virulence on wheat and caused more severe scab than low toxin potential isolates. The isolate 98-094 had highest DON potential (7.25 X I 02ug/ml) caused most severe scab on wheat (Disease grade4.0 Yangmai 158). The isolate 76-007 had lowest toxin potential caused the lightest scab (Disease grade 1.8, Yangmai 158).Filtrate of Fusarium culture medium had strong virulence on wheat. DON, a pure toxin of Fusariwn graminearum increased the virulence of Fusariwn conidium but DON injection inoculation had less virulence on wheat.With Polyacrylamide gel electrophoresis (PAGE) techniques, the difference of the soluble proteins in 6 varieties of wheat resistant or susceptible to wheat scab and the changes of these soluble proteins after treated with DON toxin were studied. The resistant varieties Sumai 3, Yangangfangzhu and Wangshuibai and the susceptible varieties Anhui 11, Alondra抯 and Yiningxiaomai were selected. The blended young heads were treated with 3 ug/ml of DON for 2 hours, 8 hours, 24 hours and 30 hours, then electrophoreses samples were prepared through grind, centrifuge and other normal methods. The results demonstrated that 3 resistant wheat varieties appeared the unique protein band of RfD...