Viability and in vitro mycorrhizal capacity of cryogenized strains of ectomycorrhizal fungi

In Mexico, wild ectomycorrhizal fungi (EcMF) are an important non-timber forest resource and are part of the traditional harvesting for self-consumption and sale. The in vitro maintenance of EcMF strains is more complex than in saprophytic species due to the physiological relationships with their hosts. This paper presents a cryopreservation method of EcMF strains using unconventional vectors and the subsequent evaluation of their viability in vitro. To this end, five ECMF strains (Boletus aff. edulis, Boletus sp., Helvella sp., and Lactarius indigo [2]) were cryopreserved (-196 degrees C) for 30 days, using sterile pine needles and millet seeds as vectors. Subsequently, the ability of two of the recovered strains to form ectomycorrhizal morphotypes in vitro inoculated in Pinus montezumae seedlings was determined. The results of the first stage showed high percentages of recovery of cryogenic mycelia in both vectors (98% - 100%). Regarding in vitro mycorrhization, non-mycorrhizal seedlings (control) did not survive, while mycorrhizal seedlings showed survival values between 33% and 100% and increases in the length of their stems. In addition, the formation of dichotomous morphotypes of dark ochre color was observed, as well as the development of the fungal mantle in the mycorrhizal roots after four months of inoculation. The method used for the cryogenization of EcMF strains allows the conservation of mycelia for prolonged periods, maintaining their mycorrhization capacity active.