State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing, China; The Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, China.
Fungal Genomics Group, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China.
Fungal Biol. 2020 May;124(5):327-337. doi: 10.1016/j.funbio.2019.10.001. Epub 2019 Oct 16.
We surveyed root endophytic fungi of the coastal halophyte Suaeda salsa and detected a population of a novel species that we described here as Laburnicola rhizohalophila sp. nov. No sexual sporulating structure was observed. Instead, it produced a large amount of thalloconidia, 0-1 transverse septa, hyaline to darkly pigmented, often peanut-shaped and sometimes dumbbell-shaped, both ends enlarged with numerous oil droplets inside the hyphal cells. Surprisingly, a high degree of phenotypic and physiological intraspecific variation (e.g., salinity tolerance, growth under different carbon:nitrogen ratios, and carbon utilization pattern) was recorded. The inoculation test indicated that the isolates could successfully infect host roots and form microsclerotia-like structures in cortical cells, a typical trait of dark septate endophytes (DSEs). Furthermore, most isolates were shown to promote host seedling growth. To evaluate conspecificity and infer its phylogenetic affinity, multiloci data including nuclear rRNA loci (ITS1 and 2, partial 28S), partial RNA Polymerase II second-largest subunit (rpb2), and partial translation elongation factor-1α (tef1) were characterized. Genealogical concordance phylogenetic species recognition (GCPSR) detected a genetically isolated clade of L. rhizohalophila within the Pleosporales in the Didymosphaeriaceae. Maximum likelihood phylogenetic reconstruction revealed that the endophytic fungus was genetically close to Laburnicoladactylidis but separated by a relatively long genetic distance. Our work highlights that the pleosporalean taxa might represent an underexplored reservoir of root DSEs.
我们调查了滨海盐生植物海蓬子的根内生真菌，发现了一个新种的种群，我们将其描述为根生内枝孢菌。未观察到有性孢子结构。相反，它产生了大量的 thalloconidia，0-1 个横向隔膜，透明至深色素，通常呈花生形，有时呈哑铃形，两端扩大，菌丝细胞内有许多油滴。令人惊讶的是，记录到了高度的表型和生理种内变异（例如，耐盐性、不同碳氮比下的生长和碳利用模式）。接种试验表明，分离株可以成功感染宿主根系，并在皮层细胞中形成类似于微菌核的结构，这是深色隔孢内生菌（DSE）的典型特征。此外，大多数分离株被证明可以促进宿主幼苗的生长。为了评估同物异性和推断其系统发育亲缘关系，我们对包括核 rRNA 基因座（ITS1 和 2、部分 28S）、部分 RNA 聚合酶 II 第二大亚基（rpb2）和部分翻译延伸因子-1α（tef1）在内的多个基因座数据进行了表征。系统发育种系发生共识识别（GCPSR）检测到在 Didymosphaeriaceae 中的 Pleosporales 中存在一个遗传上孤立的根生内枝孢菌分支。最大似然系统发育重建表明，内生真菌在遗传上与 Laburnicoladactylidis 密切相关，但通过相对较长的遗传距离分开。我们的工作强调了 pleosporalean 分类群可能代表了根 DSE 的未充分探索的储库。
