Seed endophytic microbiota in a coastal plant and phytobeneficial properties of the fungus Cladosporium cladosporioides

- Pyrosequencing analysis revealed the low diversity of seed-borne endophytic fungal community in a coastal plant.
- The genus Cladosporium dominated the seeds.
- Cladosporium cladosporioides significantly promotes host seed germination and other plant growth.

While the structure and function of the microbial communities associated with the rhizosphere and phyllosphere have received broad attention, the knowledge of seed-associated microbiota still remains limited. In this work, we characterized the seed fungal endophytes present in a coastal plant Suaeda salsa using 454 pyrosequencing. The fungal community present in its seeds exhibited extremely low species richness. Very few genera were identified, and the genus Cladosporium dominated. In parallel, we recovered one isolate of Cladosporium cladosporioides from the seeds. Hence, we hypothesized that the endophytic C. cladosporioides would exert a beneficial effect on plant fitness. Subsequent inoculation test revealed the role of C. cladosporioides in improving host seed germination rates. Re-isolation assay and scanning electronic microscopy analysis of its colonization pattern during seed germination, coupled with our previous observation that C. cladosporioides was also present in the phyllosphere, rhizosphere and root endosphere of S. salsa, supported the evidence of its primary soil-borne origin and both epiphytic and endophytic infection of host tissues. Furthermore, significant growth enhancement was recorded in American sweetgum seedlings inoculated with an optimal conidia concentration of C. cladosporioides. In conclusion, our work underscores the ecological significance of seed-borne endophytes and the system presented can be developed into a tool for understanding endophytic associations in the costal environments.