Infection process in Macrophomina phaseolina: Comparative histopathological observations between susceptible and tolerant soybean cultivars

摘要: Macrophomina charcoal rot is one of the most prevalent diseases of soybean in soybean cultivation areas. As there is no either cultural or chemical measures to manage charcoal rot in soybean, finding sources of genetic resistance is of high importance. Dissecting hostpathogen interactions provide crucial information to conduct breeding programs. Moreover, no comparative study has been performed to determine differences of the infection events in roots of resistant and susceptible soybean plants. Histopathological investigations can lead to a better understanding of the infection strategy employed by the fungus. Based on the research conducted previously, soybean cultivars, Hacheston and Williams, were selected as tolerant and susceptible ones, respectively. The 40-day plants were inoculated by the microsclerotia of the fungus and histopathological sections from inoculated roots of both cultivars were daily prepared, stained with Lacto phenol cotton blue, and eventually observed under light microscope. Histopathological observation of infected roots revealed that the interested fungus behavs differently in the tolerant and susceptible plants. The germination of the sclerotia, emerging of hyphae from germ tubes and subsequently hyphal growth was occurred on the surface of both studied cultivars with the same rate. Nevertheless, it seems that the hyphae could penetrate into the susceptible roots only three days post inoculation (dpi). The fungus completes its infection process starting from the germination of sclerotia on the surface of roots till the appearance of secondary sclerotia near the vascular cylindrical region in the susceptible cultivar …