<i>Cladophialophora novalis</i> sp. nov.: A Dark Septate Endophytic Fungus Derived from Fallow Land Soil

Endophytic fungi play essential roles in plant resilience and sustainable agriculture. Among these, dark septate endophytic (DSE) fungi are recognized for their ability to colonize plant root tissues and contribute to stress tolerance. In this study, a potential DSE isolate, designated as FX2, was obtained from agricultural soil in Tsukuba, Ibaraki, Japan. Morphological and phylogenetic analysis of the isolate showed the isolate as a novel species within the genus <i>Cladophialophora</i> (proposed as <i>C. novalis</i>). Physiological characterization revealed that <i>C. novalis</i> FX2 is sensitive to salinity, with colony growth decreasing significantly with the addition of ≥50 mM NaCl, prefers a near-neutral pH range of 5.5-7.0, and exhibits moderate drought tolerance with growth sustained up to 15% PEG. Despite <i>C. novalis</i> FX2 was isolated directly from soil, this isolate demonstrated endophytic ability without pathogenic symptoms in Chinese cabbage, maize and tomato, and increasing maize biomass significantly by 51.6% compared with uninoculated plants. These findings highlight <i>C. novalis</i> FX2 as a promising novel DSE candidate to enhance plant growth.