| Fusarium head blight and wheat stripe rust are currently two serious diseases in wheat cultivation in China. Growing disease-resistant varieties appears to be most economical and effective way to control the two diseases. However, the resistance of wheat varieties currently grown and extended in wheat production is not effective enough to Fusarium head blight, and wheat cultivars usually lost their resistance because of virulence variation and appearance of new races of wheat stripe rusts. Therefore, chemical control under proper weather conditions for diseases is still an effective measure. Since 1970's, Fungicide Carbendazim has been mainly applied to the control over Fusarium head blight, while Fungicide Triadimefon has been used for control of wheat stripe rust. The application of single chemical for a long time may cause resistance of pathogen to chemicals. To find new alternatives to those chemicals appears to be imperative. Folicur and Caramba, two triazole fungicides, have been reported to be effective to control Fusarium head blight in some countries or regions in Europe and America. There are few reports, however, in terms of the application of the two chemicals domestically in wheat diseases management. So this research is mainly trying to test the effective of fungicides Folicur and Caramber to Fusarium head blight with indoor and outdoor experiments, and then to explore the control mechanism of Folicur for Fusarium head blight by means of electronic microscopy as well as cytochemical technology. In addition, the control effects of the two fungicides, and control mechanisms of Folicur to wheat stripe rust was studied. The results and findings from the experiments are as follows: 1. Fungicides Folicur and Caramba have been demonstrated to be effective to control Fusarium head blight and can be used as the effective substitute chemicals to Carbendazim. Through the last three years experiments indoors and outdoors, it has been found that Folicur and Caramba not only can lessen the damage and extent from Fusarium head blight, but also can reduce the content of deoxynivalenol in the grains of wheat. The result of field experiment showed that Folicur and Caramba can reduce the disease index by 70-80% and 68-83%,lessen the DON content in the grain by 64-82% and 42-88% ,increase the yield by 8-22% and 11-14% respectively.In the meantime, the two chemicals, with small amount, appeared to be of long lasting effects to control wheat stripe rust and prevent the other leaf diseases.Therefore, two fungicides are the favorable alternatives to past frequently-used fungicides Carbendazim and Triadimefon. 2. The effects of Folicur on the development of Fusarium graminearum in vitro were detected through cytology and molecular cytology. Folicur not only strongly inhibited the hyphal growth of F. graminearum, but also caused a series of marked morphological and structural alterations of the hyphae. These changes included irregular swelling and excessive branching of the hyphae, considerable thickening of the hyphal cell walls, particularly at the hyphal tip region, excessive septation with incomplete septa, and necrosis or degeneration of the hyphal cytoplasm. The formations of new hyphae (daughter hyphae) inside of the collapsed hyphal cells were often detected in the cytoplasm of fungicide treated hyphae. However, the daughter hyphae also showed abnormal alterations such as irregular thickenings of the cell walls, necrosis of the cytoplasm and formation of new daughter hyphae. Furthermore, immunocytochemical labeling showed that Deoxynivalenol (DON) content greatly reduced and chitin and β-1,3-glucan in the cell walls markedly increased in the fungicide-treated hyphae as compared with the control hyphae. 3. The control mechanism of Folicur for Fusarium head blight has been studied from the perspective of cytology and molecular cytology. The research revealed that Folicur had little influence on the spore germination of Fusarium graminearum, but could postpone spore germination and make the hyphae deforme...
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