内生真菌对草坪植物病原真菌抑制作用的比较

分别从野生牧草羽茅(Achnatherum sibiricum (L.) Keng)、栽培种高羊茅(Festuca arundinacea Schreb.)(品种Millennium)、栽培种黑麦草(Lolium perenne L.) (品种Justus)中分离出内生真菌Neotyphodium sp.、N. coenophialum和N. lolli,通过体外培养法比较了这3种内生真菌对草坪植物病原真菌的抑制作用.结果表明,从羽茅中分离的内生真菌Neotyphodium sp.在两菌相交前对所有供试的病原真菌都有一定的抑制作用,其中对枝孢霉属(Cladosporium sp.)、弯孢霉属(Curvularia sp.)和拟茎点属(Phomopsis sp.)病原真菌的抑制效果尤为显著,对峙培养3d后的抑菌率分别达70.1%、52.3%和30.9%,营养竞争作用、重寄生作用是其主要的拮抗机制;从高羊茅中分离的内生真菌N. coenophialum对枝孢霉属病原真菌存在一定的抑制作用;而从黑麦草中分离的内生真菌N. lolli与病原真菌对峙培养时,病原真菌菌落慢慢侵占整个营养空间,内生真菌停止生长并逐渐褐变死亡.体外培养结果说明Neotyphodium sp.对供试病原真菌的拮抗效果优于N. coenophialum和N. lolli,由此推测Neotyphodium sp.与宿主植物羽茅的共生可能有利于宿主植物抵抗病原真菌的侵扰.

A comparative study of the inhibitive effect of fungal endophytes on turf grass fungus pathogens

Since 1866, large quantities of endophytes with metabolic activity have been isolated from almost all kinds of plants including trees, shrubs, grasses, and even from algae, moss and ferns. The grass endophytes and their hosts are mutualistic symbionts which differ from other endophytes. Studies on Neotyphodium endophytes and grasses indicate that the endophytes can not only protect the host grass from abiotic stresses but also enhance its resistance to biotic disturbances, such as herbivores and pathogens. Up to now, most research on the pathogen resistance ability of endophytic fungi has focused on endophytes isolated from non-grass medicinal plants. As for grass endophytes, limited studies have reported that endophyte-infected grasses are less frequently infected by pathogen disease. Was the resistance from endophytes themselves or from the interaction of the grass-endophyte associations? To address this question, this experiment was performed with isolated endophytes in vitro. In this paper three endophytes were used, i.e., Neotyphodium sp., N. coenophialum and N. lolli. They were isolated from Achnatherum sibiricum (L.) Keng (a native grass which was widely distributed in the Inner Mongolian Plateau), Festuca arundinacea Schreb and Lolium perenne L (cultivated grasses which were widely grown in north China lawns), respectively. Five turf grass pathogens were chosen, i.e., Fusarium sp., Rhizoctonia sp., Cladosporium sp., Phomopsis sp. and Curvularia sp., antagonistic interaction experiment, spore germination experiment and micro-cultivation experiment were carried out to address if the endophytes could resist pathogen fungi in vitro. If this is the case, what kind of antagonistic mechanisms might be involved? The results showed that endophyte Neotyphodium sp. was antagonistic to Cladosporium sp., Curvularia sp. and Phomopsis sp., and the inhibition percentages were 70.1%, 52.3% and 30.9%, respectively, after three days of inoculation. The possible mechanism involved is thought to be competitive advantage of the endophytes for nutrition and super-parasitism. The endophyte N. coenophialum had an inhibitory effect to some extent against Cladosporium sp., while N. lolli appeared to have no inhibitory effect against any of the pathogens. When N. lolli was inoculated with the pathogens, it turned brown while the pathogens took up nutritious space. The results demonstrate that Neotyphodium sp. is more antagonistic to pathogens than N. coenophialum and N. lolli, thus being beneficial to its host grass in pathogen resistance.