Department of Biological Sciences and Merriam-Powell Center for Environmental Research, Northern Arizona University, Flagstaff, Arizona 86011-5640 USA.
Am J Bot. 2014 Mar;101(3):467-78. doi: 10.3732/ajb.1400034. Epub 2014 Mar 14.
Fungal endophytes asymptomatically inhabit plant tissues where they have mutualistic, parasitic, or commensal relationships with their hosts. Although plant-fungal interactions at the genotype scale have broad ecological and evolutionary implications, the sensitivity of endophytes in woody tissues to differences among plant genotypes is poorly understood. We hypothesize that (1) endophyte communities in Populus angustifolia (Salicaceae) twigs vary among tree genotypes, (2) endophyte variation is linked to quantitative tree traits, and (3) tree genotype influences interspecific fungal interactions.
Endophytes were isolated from twigs of replicated P. angustifolia genotypes in a common garden and characterized with PCR-RFLP and DNA sequencing. Twig length and diameter, aboveground tree biomass, and condensed tannins were also quantified.
(1) Aspects of fungal community structure, including composition and total isolation frequency (i.e., abundance), varied among genotypes. (2) Aboveground biomass and twig diameter were positively associated with isolation frequency and covaried with composition, whereas twig length and condensed tannin concentration were not significantly correlated to endophytes. (3) Fungal co-occurrence patterns suggested negative species interactions, but the presence of significant co-occurrences was genotype dependent.
The species is often assumed to be the most important ecological unit; however, these results indicate that genetically based trait variation within a species can influence an important community of associated organisms. Given the dominance of plants as primary producers and the ubiquity of endophytes, the effect of host genetic variation on endophytes has fundamental implications for our understanding of terrestrial ecosystems.
真菌内生菌无症状地栖息在植物组织中，与宿主形成互利共生、寄生或共生关系。尽管在基因型水平上植物-真菌相互作用具有广泛的生态和进化意义，但木质组织中内生菌对植物基因型差异的敏感性知之甚少。我们假设：(1) 杨属（杨柳科）嫩枝中的内生菌群落因树种基因型而异，(2) 内生菌的变化与树木的定量性状有关，(3) 树种基因型影响种间真菌相互作用。
从共同园中复制的杨属基因型嫩枝中分离内生菌，并采用 PCR-RFLP 和 DNA 测序进行特征描述。还定量测定了嫩枝长度和直径、地上树木生物量和缩合单宁含量。
(1) 真菌群落结构的各个方面，包括组成和总分离频率（即丰度），因基因型而异。(2) 地上生物量和嫩枝直径与分离频率呈正相关，与组成共变，而嫩枝长度和缩合单宁浓度与内生菌无显著相关性。(3) 真菌共生模式表明存在负物种相互作用，但这种共生模式的存在取决于基因型。
通常认为物种是最重要的生态单位；然而，这些结果表明，一个物种内基于遗传的性状变异可以影响与其相关的重要生物群落。鉴于植物作为初级生产者的主导地位和内生菌的普遍存在，宿主遗传变异对内生菌的影响对我们理解陆地生态系统具有根本意义。
