禾本科植物内生真菌研究17:黄山大雀麦-内生真菌新共生体的生物学特征

Grass endophyte researches 17: biological properties of Bromus magnus-epichloid endophyte symbiosis grown in Huangshan

本研究在2011和2012年夏季从安徽省黄山市4个采样点采集大雀麦(Bromus magnus Keng)559株,镜检结果表明含菌率为48.0%～77.8%。含菌植物样品经表面消毒分离得到31株菌,根据形态学特征将这些菌株分为2个菌群:快速生长(fast growing,FG)菌群,生长速度为每周16.0～18.8 mm;慢速生长(slow growing,SG)菌群,生长速度为每周4.3～5.3 mm。FG菌群分生孢子[(4.5～5.1)μm×(2.9～3.6)μm]及分生孢子梗(15.8～24.6μm)等无性形态结构比SG菌群略大。从同一地点、同种宿主植物中分离得到分属于FG和SG菌群的不同菌株,显示出一定的遗传多样性。在基于tubB基因片段构建的系统发育树中,FG和SG菌群菌株间未表现出差异,全部菌株在Epichlobromicola/E.yangzii(EBY)中独立形成后验概率值为0.95的一支,区别于其他种的菌株,表明菌株出现生长速度显著差异的时间可能并不久远,这些菌株与大雀麦有可能是一个新的epichloid真菌-宿主植物组合。

From 2011 to 2012,559 Bromus magnus Keng plants were collected from 4 sites in Huangshan ,Anhui. The infection level was 48.0%-77.8%. Thirty-one epichloid endophyte strains were isolated on PDA plates, and these strains were divided into FG （fast growing）and SG（ slow growing）groups depended on growth rate on PDA plates. Colonies of FG strains could grow to 16.0- 18.8 mm each week,while those of SG strains were 4.3-5.3 mm. FG strains had bigger conidia（4.5-5.1 ） μmx（2.9-3.6） μm and longer phialides（ 15.8-24.6 ） μm than those of SG strains. Strains of FG and SG exhibited diversity although they were isolated from the same site and same kind of host plant. Phylogenetic tree based on tubB gene fragments revealed that strains of FG and SG clustered together in a distinct subclude within the Epichlo bromicola/E, yangzii clade, with posterior probability of 0.95. Biological properties of these strains were different from reported epichloid endophytes. It could be speculated that the significant differences of growth rate between FG and SG strains happened recently. They could be a new symbiotic association.