Infection of fusarium graminearum on wheat spikes with green fluorescence protein-tagged revertants

Chinese. 【目的】赤霉病是危害大麦、小麦生产的世界性病害，研究病原菌的致病过程对于病害的控制有重要意义。【方法】本研究利用绿色荧光蛋白（GFP）标记的禾谷镰刀菌回复突变体以单花滴注方法进行人工接种研究不同突变体的致病力差异及其在小麦穗部的侵染过程。【结果】269株回复突变体的致病力存在明显分化。接种6 d后，致病力明显降低的突变体，只有接种小穗发病，致病力明显增强的突变体，病症可扩展至5个小穗。GFP荧光信号检测表明，弱致病突变体在接种后仅在接种小穗内生长、延伸，并终止于小穗基部的致密组织处。而强致病力突变体在接种小穗内生长2 d后，即能够通过小穗基部的致密组织到达小麦穗轴，并沿着穗轴内部微管束组织和皮层组织向上和下延伸，侵入邻近小穗。【结论】病原菌在接种小穗中生长后，沿着柱头、子房或内、外稃内表面，经过靠近穗轴的致密组织，侵入邻近小穗，感染整个麦穗，直至到达茎秆。

English. [Objective] Fusarium head blight, caused by Fusarium gramiearum, is a very serious disease in wheat and barley production area. Understanding the infection mechanism of F. grarniearum plays an important role for the disease control. [Method] In present study, virulence and infection process of 269 green fluorescence protein （GFP）-tagged revertant mutants were evaluated by single floret injection and GFP screening. [Result] Results showeds distinct difference among virulent revertants. When a wheat spike was inoculated by the mutants with reduced virulence, only the injected spikelet showed symptom at 6 days past inoculation （dpi）. On the contrast, the diseased spikelets were up to 5 at 6 dpi when the spike was inoculated by the mutants with increased virulence. GFP signals indicated that mutant with reduced virulence colonized only in the inoculated spikelet and stop at the compact tissue of rachis at 6 dpi while mutant with increased virulence extended through compact tissue to rachis and infected to the adjacent spikelets by spreading upward and downward to adjacent florets inter- and intra- cellularly in vascular bundles and cortical tissue of the rachis. [Conclusion] It could be concluded that E graminearum geminated in the inoculated spikelets, grew on the top of stigma and ovary or between lemma and palea, and extended towards and through rachis to the adjacent spikelets to infect the whole spike.