Abstract
Rice false smut, caused by the ascomycete Ustilaginoidea virens, is a serious disease of rice worldwide. Conidia are very important infectious propagules of U. virens, but the ability of pathogenic isolates to produce conidia frequently decreases in culture, which influences pathogenicity testing. Here, we developed tissue media with rice leaves or panicles that stimulate conidiation of U. virens. Among the tested media, 0.10 g/ml panicle medium was most efficient for conidiation. Whereas, some rice leaf media more effectively increased conidiation than panicle media except 0.10 g/ml panicle medium, and certain non-filtered tissue media were better than their filtered counterparts. Although the conidia induced in rice tissue media were smaller, they were able to germinate on potato sucrose agar medium and infect rice normally. The rice tissue medium is also workable in inducing conidia for conidiation-defective isolates. This method provides a foundation for the production of conidia by U. virens that will be widely applicable in pathogenicity testing as well as in genetic analyses for false smut resistance in rice cultivars.
Highlights
Rice false smut (RFS), caused by the ascomycete Ustilaginoidea virens, has become one of the most destructive diseases in the majority of rice-growing regions around the world, resulting in severe field losses of rice[1,2,3,4,5] The typical symptom is smut balls informed in rice panicles, the surface of which is covered by an abundance of powdery, dark-green chlamydospores [6,7,8]
Compared with potato sucrose broth (PSB) medium, Indica rice Wanxian98 leaves or panicles media induced more conidia at individual time points. These results indicated that rice tissue could promote conidia production
The results showed that the conidia produced in PSB were larger than these produced in Indica rice leaf (IRL), Indica rice Wanxian98 panicle (IRP), Japonica rice leaf (JRL) and Japonica rice panicle (JRP) media (Table 3)
Summary
Rice false smut (RFS), caused by the ascomycete Ustilaginoidea virens, has become one of the most destructive diseases in the majority of rice-growing regions around the world, resulting in severe field losses of rice[1,2,3,4,5] The typical symptom is smut balls informed in rice panicles, the surface of which is covered by an abundance of powdery, dark-green chlamydospores [6,7,8]. U. virens can overwinter with thick-walled chlamydospores and sclerotia, the latter can produce sexual ascospores. Both ascospores and chlamydospores germinate and produce secondary conidia, which are the sources of primary infection in rice [12,13,14]. Some studies have indicated that U. virens can infect roots and other rice tissues [15,16,17].
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