Species diversity of vesicular-arbuscular mycorrhizal fungi of teak (Tectona grandis Linn. F.) and their effects on growth of teak seedlings

Diversity of vesicular-arbuscular mycorrhizal fungi was studied in soils collected from 2 teak plantations: the Teak Plantation of Mae Klong Watershed Research Station, Thong Pha Phoom District, Kanchanaburi and the Mae Moh Plantation, Ngao District, Lampang, Soils were also collected from teak seedling pots produced by Klang Dong Plantation, Pak Chong District, Nakornratchasima and Tha Muang Plantation, The Muang Distric, Kanchanaburi. Altogether 6 species of vesicular-arbuscular mycorrhizal fungi were found in these soils, namely, Acaulospora scrobiculata Trappe, Glomus aggregatum Schenck & Smith emend. Koske, Gl. deserticola Trappe, Bloss & Menge, Gl. multicaulis Gerdemann & Bakshi, Sclerocystis microcarpus lqbal & Bushra and an unidentified species (black spore). The species diversity and number of spores of each species varied in each soil sample. Soil collected from the Teak Plantation of Mae Klong Watershed Research Station contained the highest species diversity and total number of spores. Spores of these fungi were reproduced in soils planted with corn or teak seedlings, but corn was a better host than teak. Six month-old teak seedlings inoculated with these 6 species of fungi showed greater height, diameter at root collar, shoot dry weight, root dry weight and total dry weight than noninoculated seedlings. Most of the differences in these growth parameters were statistically significant. All fungi also increased the efficiency of nitrogen, phosphorus and potassium uptake in teak seedlings but were not significantly different statistically. Analysis of seedling growth performance indicated that seedlings inoculated with A. scrobiculata, Gl. aggregatum, Gl. deserticola and an unidentified species (black spore) attained the highest seedling quality. However, spores of the unidentified species (black spore) were reproduced in soils planted with corn or teak seedlings significantly fewer than spores of the first 3 fungi. Therefore, for future teak planting programs it is recommended that any of the 3 fungi is suitable for mass production and inoculation into teak seedling roots. Further research should be carried out for the unidentified species (black spore) in order to know its name, suitable host and optimal environmental condition for reproduction.