共生真菌对兰科植物种间杂交后代种子萌发的效应

Effects of symbiotic fungi on seed germination of interspecific hybrid progenies in Orchidaceae

石斛属(Dendrobium)植物在种子共生萌发过程中与真菌有着较为专一的共生关系,为探讨这种共生关系在种间杂交后代上的进化和适应,深入理解兰科植物和真菌共生关系的形成机制,该研究利用能有效促进铁皮石斛(Dendrobium officinale)和齿瓣石斛(D.devonianum)种子萌发形成幼苗,并具有较强专一性的胶膜菌属(Tulasnella)真菌SSCDO-5和瘤菌根菌属(Epulorhiza)真菌FDd1,开展真菌对铁皮石斛和D. tortile种间杂交种子萌发效应的研究。结果表明,在真菌与种子共生培养68天时,SSCDO-5菌株和FDd1菌株都能有效地促进杂交种子形成原球茎和幼苗,两个接菌处理之间无显著差异,来源于铁皮石斛的SSCDO-5菌株不但没有表现出优势,反而在杂交石斛幼苗形成率上低于来源于齿瓣石斛的FDd1菌株(SSCDO-5:(22.13±6.62)%;FDd1:(29.53±5.51)%);SSCDO-5菌株和铁皮石斛在幼苗形成和发育阶段的共生专一性并没有在杂交后代上得到遗传或表现,或者说是杂交打破了这种专一性的共生关系,使得杂交后代能够和不同的真菌建立新的共生关系。该结果不支持关于共生真菌专一性是石斛属植物杂交后代形成的重要限制因素的假设,推测石斛属植物在幼苗分化和发育阶段与真菌这种专一性的共生关系是在适应特定生态环境的过程中形成和建立的。

Aims Previous studies have shown that Dendrobium plants form a specific symbiotic relationship with fungi at differentiation stages during natural seed germination.In order to explore the evolution and adaptation of this symbiotic relationship in interspecific hybrid progenies,this study was to understand whether the strong specificity with symbiotic fungi during seedling formation and differentiation was also an important factor limiting the formation of hybrid progenies in Dendrobium,and the relationship between hybrid progenies of orchids and symbiotic fungi during seed germination stage.Methods The effects of fungi on germination of interspecific hybrid seeds of D.officinale and D.tortile were studied using the highly specific fungi strains Tulasnella SSCDO-5 and Epulorhiza FDd1,which can effectively promote seed germination and seedling formation in D.officinale and D.devonianum,respectively.Important findings The results showed that both SSCDO-5 and FDd1 strains could effectively promote the protocorm and seedling formation of hybrid seeds after 68 days incubation with no significant difference.The SSCDO-5 strain from D.officinale did not show any advantages,and the seedling formation rate of hybrid was lower than that of FDd1 strain from D.devonianum.The seedling formation rate incubation with SSCDO-5 strain was(22.13±6.62)%while with FDd1 strain was(29.53±5.51)%.The specificity of SSCDO-5 strain with D.officinale at seedling formation and development stage was not inherited or expressed in hybrid progenies,indicating that hybridization broke the symbiotic relationship of this specificity,which enabled hybrid progenies to establish new symbiotic relationship with different fungi.Our results do not support the hypothesis that the specificity of symbiotic fungi is an important limiting factor for the formation of hybrid progenies in Dendrobium.We speculate that the symbiotic relationship between Dendrobium plants and fungi during seedling differentiation and development is formed and established in the process of adapting to specific ecological environment.