Dark septate and arbuscular mycorrhizal fungal endophytes in roots of prairie grasses

Abstract

Root symbioses with dark septate endophytic fungi (DSE) and arbuscular mycorrhizal fungi (AMF) provide plant tolerance to environmental stresses. This research answers several fundamental questions about the occurrence of these fungi in roots of prairie grasses. Traditional methods and current molecular techniques were combined in order to: 1) define the role and specificity of DSE in plant tolerance to drought; 2) assess the level of host specificity in DSE; 3) document AMF biodiversity and pattern of root colonization at different soil depths; 4) define the influence of soil depth and plant species on the distribution of DSE and AMF in roots and; 5) reveal how DSE and AMF interact in plant roots.

Under controlled conditions, DSE isolates showed host preference in colonizing roots and promoting plant growth. They colonized with more intensity the plant species from which they were isolated [Agropyron cristatum L. or Psathyrostachys juncea (Fisch) Nevski subsp. Juncea (Syn: Elymus junceus Fisch)]. Inoculation with five DSE isolates resulted in growth stimulation of the C3 grasses A. cristatum and P. juncea, and growth depression of the C4 grass Bouteloua gracillis (Willd. ex Kunth) Lag. ex Griffiths, under water stress. Plant C concentration suggested that DSE inoculation may have resulted in net C drain from B. gracillis.