Preliminary study on Gramineae resistance to Sclerotinia sclerotiorum

摘要

Sclerotinia sclerotiorium (Lib.) de Bary is a ubiquitous necrotrophic fungal pathogen capable of infecting at least 408 plant species of 75 families. No highly resistant variety or germplasm is found in hosts including Cruciferae plants. In Brassica napus,the disease results in severe yield losses. But in non-host plants such as some Gramineae species, the pathogen is avirulent or weakly virulent developing no lesions or very small ones before dying or forming sclerotia. To understand how these non-hosts resist the pathogen, we inoculated S. sclerotiorium mycelium onto the leaves of bamboo, wheat, maize and oilseed rape. Different responses were observed in these plants after 24 hpi (hours post inoculation). No lesion was found on bamboo and maize leaves.Small lesions were observed on wheat, but the lesion size varied among different cultivars. Larger lesions were observed on oilseed rape leaves than any other Gramineaes at earlier time after inoculation. Scanning electron microscope (SEM) clearly showed a layer of membrane glutinous to the bamboo surface, and transverse sections of infected leaves under optical microscope unveiled hyphae penetrating the epidermal cell The modes that hyphae grew into the leaves were also different between bamboo and oilseed rape. They grew mainly under the oilseed rape epidermal and in the intercellular space, while limitedly in epidermis and mesophyll cells in bamboo leaves. We assumed that surface substance and cell wall composition ware obstacles to S.sclerotiorium hyphae in non-host Gramineae plants. Further work needs to be done to analyze these compounds in comparison with oilseed rape and interaction between the pathogen and bamboo leaf.