Abstract and subjects
Diverse fungi colonize plant roots worldwide and include species from many orders of the phylum Ascomycota. These fungi include taxa with dark septate hyphae that colonize grass roots and may modulate plant responses to stress. We describe a novel group of fungal isolates and evaluate their effects on the grass
in vitro. We isolated fungi from roots of six native grasses from 24 sites spanning replicated latitudinal gradients in the south-central US grasslands and characterized isolates phylogenetically using a genome analysis. We analyzed 14 isolates representing a novel clade within the family Montagnulaceae (order Pleosporales), here typified as
, closely related to the genera
and
. This novel species produces asexual, light brown pycnidium-like conidioma, hyaline hyphae, and chlamydospores when cultured on quinoa and kiwicha agar. To evaluate its effects on
, seeds were inoculated with one of three isolates (DS304, DS334, and DS1613) and incubated at 25 C for 20 d. We also tested the effect of volatile organic compounds (VOCs) produced by the same isolates on
root and stem lengths. Isolates had variable effects on plant growth. One isolate increased
root length up to 34% compared with uninoculated controls. VOCs produced by two isolates increased root and stem lengths (
< 0.05) compared with controls. Internal transcribed spacer ITS2 metabarcode data revealed that
is distributed across a wide range of sites in North America (22 of 24 sites sampled), and its relative abundance is influenced by host species identity and latitude. Host species identity and site were the most important factors determining
relative abundance in drought experiments at the Extreme Drought in the Grasslands Experiment (EDGE) sites. Variable responses of
to inoculation highlight the potential importance of nonmycorrhizal root-associated fungi on plant survival in arid ecosystems.