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Infection process of Villosiclava virens on rice
J. H. Song (1), C. LUO (1). (1) Huazhong Agricultural University, Wuhan, China

Rice false smut disease caused by the fungus <i>Villosiclava virens </i>is an increasing threat to rice production in the world. The infection process of<i> V. virens </i>is not yet completely understood despite best efforts. In the present study, the infection process of GFP-labeled strain G2 in rice spikelets was monitored. At 1 to 3 day post inoculation (dpi), conidia germinated at the outer surface of spikelets and fungal hyphae extended to the interior of spikelets mostly from the apices of the spikelets, some hyphe also entered spikelets through cracks at the middle or basal part of the lemma and palea, finally reached the floral organs, e.g., filaments, styles and lodicules. At 4 to 7 dpi, filaments were firstly observed to be infected, then stigmas and styles were covered and gradually infected by fungal mycelia. Over the next days, fungal mycelia developed quickly and covered all of the floral organs. Under scanning electron microscopy, infection sites were observed on the surface of stigmas and styles, and the inner space of style tissue was found to be filled with hyphae under transmission electron microscopy. After invading the styles, fungal hyphae extended to the intercellular space but did not penetrate into host cells. At the later stages, many host cells in styles appeared to be digested. Although a few ovaries were infected by the fungal mycelia via infected styles, in most of the infection, the mycelia did not reach ovaries.

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