来源对丛枝菌根真菌功能的影响

Effects of origin on the functioning of arbuscular mycorrhizal fungi

丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)是一种具有重要生态功能的根际微生物。影响AMF功能的因素主要包括AMF、宿主,以及其它生物与非生物环境。近年来,大量研究表明不同来源的AMF功能存在显著差异。结合该领域的最新研究成果,从基因变异和表型可塑性两方面分析了来源影响AMF功能的原因和维持机制,并对其生态学意义进行了探讨。认为应从群落水平上研究不同来源的AMF在生态系统中的功能,重视宿主的作用,保持研究对象的对等性,并区分AMF群落结构和来源对功能的不同影响。对未来的研究重点和方向进行了讨论和展望,试图为更加清晰、全面地认识AMF在生态系统中的功能,以及AMF适应特定土壤环境与宿主的机制提供参考。

The ubiquitous arbuscular mycorrhizal fungi （AMF） form obligate symbiotic associations with the roots of more than 80% terrestrial plants. AMF play multiple ecologically important roles in various ecosystems. In exchange for carbon, AMF assist the host plant in acquiring mineral nutrients （especially for the less mobile element, phosphorus）, enhance stress tolerance, provide ＂bio-protection＂ from soil-borne pathogens and mediate plant-plant interactions. The effectiveness of AMF in carrying out their ecological role （s） depends on the compatibility between AMF and host plant, and also the corresponding biotic/abiotic environments. In the past decades, there is ample evidence to suggest that in most cases AMF from different origins were significantly different in their effectiveness on host plants. Here, we reviewed the effects of fungal origin on AMF functioning, analyzed its causes, maintenance mechanisms, and ecological significance based on the novel interests and latest advancements. The functional differences could occur among both AMF species and among different isolates of the same species. In general, the native AMF isolates performed better and were more efficient in promoting plant growth when compared to the exotic counterparts, although contradictory results were also reported. At present, however, there were several problems that were not addressed properly in most of the previous studies. Firstly, the disparities of AMF effects on plant performance were rarely measured at the whole community level. AMF typically occur as extensive fungal assemblages in nature, and will colonize most if not all the plant roots simultaneously within the community The behavior and functioning of a mixture of AMF species are very different to a single species partly due to the functional complementarity, synergistic relationships and competition between various AMF species. Therefore, the community level comparison of AMF functioning is more relevant to the actual field situations. Secondly, the comparisons between different AMF species or single AMF species and community from different origins are probably not useful, as they are intrinsically different by nature. Thirdly, it is incorrect to attribute the functional variation of naturally occurring AMF communities exclusively to their origins, the influences of origin, and structure of AMF communities should be considered as equally important and distinguished explicitly. Fourthly, the effects of host plant or even neighboring plant on AMF functioning should not be ignored as they are likely to change the AMF genotype, phenotype and the associated community structure. The significance of origin in AMF functioning could probably be attributed to the differences in soil physiochemical property and host identity. AMF are characterized by multi-genome inheritance and are susceptible to nuclei segregation and genetic recombination. Perturbations in soil and host will induce rapid genetic variation and this may encourage phenotypic plasticity in AMF at the individual level, or cause structural change at the community level. Finally, we suggest that （ 1 ） a combined method of traditional AMF spore counting and molecular analysis of AMF community colonizing plant roots should be used; （2） long-term monitoring and assessment are clearly needed considering the differences of various AMF in adaptability ; （ 3 ） more attentions should be paid on the effects of AMF on plant-plant interactions and ecological processes rather than focusing on an individual plant. This review article examines the current understanding of the roles AMF play in ecosystems and discusses how a given AMF community is better matched ecologically to its local soil condition and plant habitat than communities from foreign geographical sources.