The Pathogenicity of Sclerotium rolfsii on Cyperus difformis and its Potential Host Specificity among the Genus Cyperus

Abstract

Sclerotium rolfsii Sacc. infects more than 500 species of monocotyledonous and dicotyledonous plants except Cyperaceae family. The pathogenicity of a S. rolfsii isolate was evaluated by seven Cyperus species in order to explicate host specificity to Cyperaceae family. The results showed that only C. dofformis L. was infected with typical water-soaked lesions of the basal stem, which progressed to rotting, wilting, blighting, and eventually death. The performance of hyphae on the surface of Cyperus plants was compared and found that only stomata of C. difformis were adhered by hyphae of S. rolfsii. The infection process of S. rolfsii on leaf sheath of stem base in C. difformis showed that dense mycelial networks and ramifying hyphae were usually formed on the inoculated tissues, then growing hyphal tips were observed to spread wavelike on the stem surface, reaching the stomata between the leaf veins accurately and directly enter the host through stomata. Differences of the main micro-morphology characters of leaf sheath abaxial epidermis among the seven species were compared. The stomata of C. difformis were always presented between the leaf veins (3 or 4 rows of cells from the leaf veins), while the stomata of tolerant Cyperus species were close to the leaf veins. Underneath the stromata of C. difformis were air chambers, however vascular bundles were always present underneath the stomata of the tolerant Cyperus. Our study indicates that different anatomical structures in genus Cyperus may be associated with resistance to S. rolfsii infection.