Fungal endophytes of P. annua growing in Antarctica

Invasive plants may cause a negative impact to native species due to competition for resources. This is the case of Poa annua, the only non-native plant species successfully established in Maritime Antarctica. Therefore, it is important to understand which factors could be driving the competitive success of P. annua, even despite the harsh environmental conditions. One of such factors is the establishment of novel mutualistic relationships with the resident soil fungi, which would improve plant growth and confer protection against stressful conditions. Additionally, plant-associated (endophytic) fungi could also participate in seedling development and establishment, by being vectored in seeds. Therefore, in this study we explored the composition and compared the diversity of fungal communities in different P. annua tissues (seeds, leaves and roots) with representative samples of Antarctic tundra soil by using ITS2 sequencing. Our results suggest that P. annua would have a strikingly different microorganism community compared with Antarctic soil, as only 6 amplicon sequence variants were shared among plants and soils; therefore, it is plausible that the invasive success of P. annua is mediated by its' unique endophytes (rather than soil fungi).

外来入侵植物会因资源竞争对本土物种产生负面影响。南极海洋性地区成功定殖的唯一非本土植物物种一年生早熟禾（Poa annua）便是如此。因此，即便身处严苛的环境条件下，解析驱动一年生早熟禾（P. annua）竞争成功的关键因子仍具有重要意义。其中一类关键因子便是其与本土土壤真菌建立全新的互利共生关系，该关系可促进植物生长并增强其对胁迫环境的耐受能力。此外，与植物共生的内生真菌（endophytic fungi）还可通过种子携带的方式参与幼苗的生长发育与定殖过程。鉴于此，本研究采用ITS2测序技术，对一年生早熟禾（P. annua）不同组织（种子、叶片及根系）中的真菌群落组成进行解析，并与南极苔原代表性土壤样本的真菌群落多样性开展对比分析。研究结果显示，与南极土壤相比，一年生早熟禾（P. annua）的微生物群落组成存在显著差异：仅存在6个共享于植物与土壤样本的扩增子序列变异体（amplicon sequence variant, ASV）。由此可推测，一年生早熟禾（P. annua）的入侵成功并非依赖土壤真菌，而是由其独特的内生真菌所介导。