叶退化型附生兰科植物菌根真菌的多样性及营养适应意义

The family Orchidaceae comprises a group of plants with great economical and ecological value, which can form mycorrhizal symbiosis with fungi. Species with vestigial leaves can be found in both terrestrial and epiphytic orchids. The loss or reduction of leaves may lead to lower photosynthetic efficiency of these orchids, making them more dependence on their mycorrhizal symbionts to survive. Previous studies have shown that several terrestrial orchids with vestigial leaves are myco-heterotrophs, and they can harbor significantly different mycorrhizal fungi when compared with their closely related species. However, little is known about the trophic type and mycorrhizal symbionts of vestigial-leaved epiphytic orchids (VLEO), which usually grows in a habitat with limited nutrients. In this project, we select four epiphytic orchids with different leaf features, two leafless, one with reduced leaves and one with large leaves, from the tribe Aeridinae to study their associations with mycorrhizal fungi. We aim to: (i) elucidate the diversity and community composition of mycorrhizal fungi associated with VLEO and their large-leaved relative, by Sanger sequencing for fungal strains isolated from these plants and High-throughput sequencing for the roots of these orchids; (ii) estimate the nutrition strategy of these VLEO through photosynthetic activity measurement and natural abundance detection of 13C and 15N isotope; and (iii) test if carbon absorption efficiency of seedlings of these orchids varies with different culture media and different fungal inoculations in symbiotic cultivation through 13C isotope tracing. This work will be vital to address the relationships among VLEO and their mycorrhizal symbionts and the functional roles of mycorrhizal fungi in adaptation of plants to nutrient of epiphytic habitat. The outputs of this project will provide novel knowledge on the conservation and sustainable utilization of species resources in Orchidaceae.

兰科植物具重要的经济和生态价值，并与真菌结成紧密的共生关系。该科某些物种的叶片退化，这可能降低植物的光合能力，使植物在碳营养上更依赖于共生真菌。研究表明，地生型兰科植物中的叶退化物种均为真菌异养型，其共生真菌与叶发达型的明显有别。对常生于贫瘠生境中的叶退化附生兰，其菌根真菌组成和营养策略尚缺乏研究。本研究拟以指甲兰亚族4种附生兰（近无叶的2种，叶退化的1种，叶发达的1种）为研究对象，开展以下三方面研究：①通过植物菌根高通量测序和真菌菌株的Sanger测序对菌根真菌进行鉴定，明确附生型叶退化兰科植物的菌根真菌多样性和群落结构；②通过检测野生植株的碳氮稳定同位素和光合活性认识叶退化型附生兰科植物的营养策略；③通过共培养和碳同位素示踪实验，认识菌根真菌对叶退化附生兰幼苗碳营养获取的影响。从而认识菌根真菌与叶退化型附生兰科植物的共生关系及其在植物养分适应中的意义，为物种资源保护和利用提供理论依据。

兰科植物具重要的经济和生态价值，并与真菌结成紧密的共生关系。该科部分物种的叶片退化，这可能降低植物的光合能力，使植物在碳营养上更依赖于共生真菌。研究表明，地生型兰科植物中的叶退化物种均为真菌异养型，其共生真菌与叶发达型的明显有别。对常生于贫瘠生境中的叶退化附生兰，其菌根真菌组成和营养策略尚缺乏研究。本项目以我国分布的叶退化附生兰（指甲兰亚族三个属共7个物种，分别为异型兰、白花异型兰、广东异型兰、黄绿异型兰、带叶兰、尖囊蝴蝶兰和华西蝴蝶兰）为对象开展菌根真菌研究。研究发现：①我国叶退化附生兰科植物的菌根真菌主要为角担菌科真菌，异型兰属、带叶兰属和蝴蝶兰属无叶组在菌根菌多样性和菌群组成上较为相似，不同属、种间共享大量菌根真菌，真菌宿主专一性不明显，这可能与三属均为混合营养型（通过光合作用和菌根真菌获取营养）相关。②异型兰菌根中分离的角担菌科真菌能够促进异型兰和华西蝴蝶兰种子萌发，而胶膜菌科未促进种子萌发；角担菌科真菌对异型兰幼苗生长的影响与碳源相关。本研究有助于深入认识兰科附生植物的菌根共生关系及生态适应机制，同时也为物种资源保护和利用提供了理论依据。已发表SCI论文3篇，协助培养研究生2名。