Morphological and Molecular Profiling of <em>Cercophora </em>sp. with its Potential to Enhance Legume Growth Under Drought

Drought is one of the critical environmental constraints limiting legume production worldwide. Although the ecological roles of dark septate endophytes (DSE) in enhancing plant growth and stress resistance have been widely investigated, most studies have focused on a few well-known genera, leaving the functional diversity of other taxa largely unexplored. Among these, Cercophora species, typically known as saprobic or coprophilous fungi, have occasionally been isolated from plant roots, yet their potential as endophytes remains unclear. This study aimed to isolate and characterize Cercophora sp. strains from agricultural soils with different fertilization histories, and evaluate their effects on legume growth under drought conditions through controlled inoculation experiments on mung bean and clover. Given their melanized, septate hyphae and slow growth, Cercophora sp. may possess physiological traits enabling them to form root associations similar to those of other DSE. Among the isolates obtained, Cercophora sp. exhibited the most consistent growth-promoting effects on the mung bean and clover. Inoculation with Cercophora sp. significantly increased shoot and root mass, chlorophyll content, and root elongation under both optimal and water-limited conditions. These findings provide the first evidence that Cercophora sp., considered a saprobic fungus, can act as a beneficial root-associated fungus enhancing legume performance under drought stress.