Arbuscular Mycorrhizal Fungus Diversispora spurcum Improved the Growth and Freeze Tolerance of Mongolian Crested Wheatgrass (Agropyron cristatum)

Agropyron cristatum (L.) Gaertn. (crested wheatgrass) is an endemic grass species, which dominates the Mongolian steppe. In this study, spores of arbuscular mycorrhizal fungi (AMF) in the rhizosphere soil of crested wheatgrass were isolated with wet-sieving/decanting methods and sucrose density gradient centrifugation, and the associated species was identified as Diversispora spurcum C. Walker & Schuessler. An arbuscular-mycorrhizal resynthesis experiment showed that D. spurcum formed arbuscular mycorrhizae with crested wheatgrass seedlings, and promoted their growth and biomass. The dependency of the crested wheatgrass on arbuscular mycorrhizae (AMs) with D. spurcum was 292%. Diversispora spurcum inoculation also significantly increased the nitrogen and mineral (P, K, Ca, Mg, and Na) contents in roots, stems, and leaves of crested wheatgrass. Inoculated and non-inoculated crested wheatgrass seedlings were cold-acclimated and subsequently subjected to freeze tolerance tests at -8, -11, -14, -15, -16, and -17℃, respectively. The leaf lethal temperatures for 50% mortality (LT50) of non-inoculated and inoculated crested wheatgrass were -8 and -14℃, respectively, while the whole plant LT50 values of non-inoculated and inoculated crested wheatgrass were -11 and -15.5℃, respectively. These results demonstrated that D. spurcum could effectively form arbuscular mycorrhizae with crested wheatgrass and improve its growth, presumably through enhanced nutrition acquisition, and freeze tolerance.