Cytopathological Studies On The Relationship Of Curvularia Lunata (Wakker) Boed. And Maize

Maize leaf spot infected by Curvularia lunata (Wakker) Boedis one of the most important diseases of poplar in the north of china recently. Since it was found in seaboard of Shandong from the end of 1970s to the beginning of 1980s, it has spread out toward many regions, and caused great yield loss in maize. In this paper, the infection and the main cellular events during the pathogen colonization were observed by means of electron microscopy and cytochemical labeling techniques. It was observed by electron microscopy that one germ tube, occasionally along with two, development from a germinated spore. The germ tube grew rapidly and formed considerable branched. The penetration of germ tube passed through epidermal cell but not stomata. After invasion of the pathogen into host, intercellular hyphae extended at first between host cells, then infected dead host cells and produced intracellular hyphae in host cells. During extension of the hyphae, series of pathological changes in the infected tissues of the host were observed, and the host cells died and digested finally, probably resulting from the toxin secreted by the pathogen. The cell wall components cellulose, xylan, spectin in cell walls of uninoculated healthy and C.lunata-infected leaf tissue were detected by means of cytochemical technique. It showed that the labeling densities for cellulose, xylan, spectin were significantly reduced as compared with corresponding cell walls of healthy leaf issue, indicating that C.lunata secreted cell wall-degrading enzymes such as cellulases, xylanases, pectinases during infection of the leaf issue, which decomposed and softened the host cell walls, then contributed to the penetration and extension of pathogen.The effects of triadimefon, a systemic fungicide from the triazol group, were examined on morphology, structure and cell wall components of Curvularia lunata by means of electron microscopy and cytochemical labelling techniques. The studies revealed that triadimefon not only inhibited the hyphal growth but also caused a series of marked morphological and structural alterations of hyphae. These changes included irregular swelling, excessive branching and many tumors on the surface of hyphae, considerable thickening of the hyphal cell walls, particularly at the hyphal tip region. The septum development of the hyphae was inhibited and became malformed. Forthermore,using cytochemical techniques, the labelling densities of chitin and -1,3- glucan in the cell wall of the fungicide-treated hyphae were decreased dramatically comparing with those of the control hyphae, indicating that the detrimental effects of the fungicide on structure and function of the hyphal membranes changes compositions of the cell walls.Maize species were evaluated for the resistance to the Curvularia leaf spot in seedling英文摘要and flowering stage after inoculation compared to Yedan13. The SSR results showed that there were differences in resistance level among species. Species Danyul3, Zhongdanl, Shandan911, Nongda60, Xinongll, Qin4 in seedling stage and species Xinong11, Shen10, Yu22, Danyu13, 7098 in flowering stage performed better resistance, respectively. Xinongl 1 and Danyu13 were resistant in both seedling and flowering stage.