Lazar Anna, Mushinski Ryan M, Bending Gary D
School of Life Sciences, The University of Warwick, Coventry, CV4 7AL, UK.
Environ Microbiome. 2022 Jul 25;17(1):40. doi: 10.1186/s40793-022-00431-3.
The genus Tetracladium De Wild. (Ascomycota) has been traditionally regarded as a group of Ingoldian fungi or aquatic hyphomycetes-a polyphyletic group of phylogenetically diverse fungi which grow on decaying leaves and plant litter in streams. Recent sequencing evidence has shown that Tetracladium spp. may also exist as root endophytes in terrestrial environments, and furthermore may have beneficial effects on the health and growth of their host. However, the diversity of Tetracladium spp. communities in terrestrial systems and the factors which shape their distribution are largely unknown.
Using a fungal community internal transcribed spacer amplicon dataset from 37 UK Brassica napus fields we found that soils contained diverse Tetracladium spp., most of which represent previously uncharacterised clades. The two most abundant operational taxonomic units (OTUs), related to previously described aquatic T. furcatum and T. maxilliforme, were enriched in roots relative to bulk and rhizosphere soil. For both taxa, relative abundance in roots, but not rhizosphere or bulk soil was correlated with B. napus yield. The relative abundance of T. furcatum and T. maxilliforme OTUs across compartments showed very similar responses with respect to agricultural management practices and soil characteristics. The factors shaping the relative abundance of OTUs homologous to T. furcatum and T. maxilliforme OTUs in roots were assessed using linear regression and structural equation modelling. Relative abundance of T. maxilliforme and T. furcatum in roots increased with pH, concentrations of phosphorus, and increased rotation frequency of oilseed rape. It decreased with increased soil water content, concentrations of extractable phosphorus, chromium, and iron.
The genus Tetracladium as a root colonising endophyte is a diverse and widely distributed part of the oilseed rape microbiome that positively correlates to crop yield. The main drivers of its community composition are crop management practices and soil nutrients.
四枝孢属（Tetracladium De Wild.，子囊菌门）传统上被视为一类英戈尔氏真菌或水生丝孢菌——这是一组系统发育多样的真菌，生长在溪流中腐烂的树叶和植物残体上。最近的测序证据表明，四枝孢属物种也可能作为陆地环境中的根内生菌存在，而且可能对其宿主的健康和生长具有有益作用。然而，陆地系统中四枝孢属物种群落的多样性以及影响其分布的因素在很大程度上尚不清楚。
利用来自英国37个甘蓝型油菜田的真菌群落内部转录间隔区扩增子数据集，我们发现土壤中含有多样的四枝孢属物种，其中大多数代表以前未表征的进化枝。两个最丰富的可操作分类单元（OTU），与先前描述的水生叉状四枝孢（T. furcatum）和颚状四枝孢（T. maxilliforme）相关，相对于根际土壤和土体土壤，在根中更为富集。对于这两个分类单元，根中的相对丰度与甘蓝型油菜产量相关，而根际或土体土壤中的相对丰度则不然。在不同隔室中，叉状四枝孢和颚状四枝孢OTU的相对丰度在农业管理实践和土壤特性方面表现出非常相似的响应。使用线性回归和结构方程模型评估了影响根中与叉状四枝孢和颚状四枝孢OTU同源的OTU相对丰度的因素。根中颚状四枝孢和叉状四枝孢的相对丰度随pH值、磷浓度以及油菜轮作频率的增加而增加。它随土壤含水量、可提取磷、铬和铁浓度的增加而降低。
四枝孢属作为一种定殖于根部的内生菌，是油菜微生物组中一个多样且分布广泛的部分，与作物产量呈正相关。其群落组成的主要驱动因素是作物管理实践和土壤养分。
