Effect of Mycorrhizae on Germination and Seedling Growth Rate of Native Tree Species at Doi Suthep-Pui National Park and Chiang Mai University

ABSTRACT: The effects of vesicular-arbuscular mycorrhiza on germination and growth rate of 5 tree species were investigated: Bauhinia purpurea Linn., Toona ciliata M. Roem, Peltophorum dasyrachis Miq. Kunz, Turpinia pomifera DC. and Melia toosendan Sieb & Zuee. Seeds of M. toosendan and T. pomifera trees, were collected in Doi Suthep-Pui National Park whilst seeds of the other three species were collected on Chiang Mai University campus. Three germination-media treatments were applied: i) soil from around the roots of the adult trees was used. ; ii) sterilized soil and iii) sterilized soil inoculated with the mycorrhizal fungus: Glomus micropus. A pilot study was carried out to determine the condition required to sterilize soil. The most effective sterilization method was 1/2 kg of soil placed in an autoclave at 121oC, 15 pound / inch 2 for 3 hours.

Only three species germinated and survived: B. purpurea, T. ciliata and T. pomifera. Mycorrhiza had no effect on the percent germination rate. But soil sterilization increased germination rate of T. ciliata (p = 0.05). Inoculation of soil with G. microcarpus had no significant effect on any of the variables measured, except percent root infection of seedlings at the end of the experiment, which was significantly increased (p< 0.05). Soil sterilization significantly increased germination of T. ciliata and increased height and growth rate of B. purpurea and T. ciliata. It is likely that sterilization had its effects via eradicating pathogens from the soil.