荸荠茎点霉秆枯病菌侵染过程的超微观察

Ultrastructural observation of infection process of Phoma bellidis causing stem blight of Eleocharis dulcis

荸荠（Eleocharis dulcis），又称马蹄，为莎草科多年生草本植物，是一种具有食用和药用价值的水生蔬菜。近年来，随着荸荠在我国种植面积的不断扩大，病害发生也呈逐年上升趋势。

The present work demonstrates infection process of Phoma bellidis on Eleocharis dulcis. Conidial suspensions of the fungus were inoculated onto healthy stems of resistant cultivar Xiangtan and susceptible culti- var Lushan, respectively, and the infection process was observed by scanning electron microscopy. Conidia star- ted to germinate with one or more germ tubes at 6 hours post inoculation （hpi）. At 12 hpi, the germ tubes pene- trated into epidermal cells directly, penetrated cuticle by forming a cushion-shaped appressorium or entered into cell through the opened stomata. Direct penetration was the most frequent style for P. bellidis infection. The pene- trated hyphae could also form branches for further infection of host cells. At 24 hpi, no significant difference in conidial germination rate was found between resistant and susceptible cultivars, while significant differences were observed in both length of germ tube and infection rate. Lower penetration rate might be an important fac- tor for resistance of cultivar Xiangtan which caused： unsuccessful penetration of germ tube to grow continuously on the surface of host cells. This is the first report of the infection process of Phoma bellidis on host plant.