MYCORRHIZAL DEPENDENCY OF 2 HAWAIIAN ENDEMIC TREE SPECIES - KOA AND MAMANE

Vesicular-arbuscular mycorrhizal (VAM) fungi have been proposed as a l ow-input solution to the problem of inadequate phosphorus (P) levels i n many tropical and subtropical soils. To determine the mycorrhizal de pendency of two Hawaiian endemic tree species, mamane (Sophora chrysop hylla Seem.) and koa (Acacia koa Gray), seedlings were grown in the gr eenhouse with and without the VAM fungus, Glomus aggregatum Schenck an d Smith emend Koske, at three levels of soil solution P (0, 0.02, and 0.20 mg P/L) in a volcanic ash soil. Inoculation significantly increas ed colonization of roots by the VAM fungus in both mamane and koa seed lings. At 0.02 mg P/L, mamane inoculated with the VAM fungus had signi ficantly greater subleaflet P concentrations at 48 days after planting (DAP), and significantly greater leaf areas, shoot dry weights, and r oot lengths at harvest compared to uninoculated plants. At 0 mg P/L, k oa grown in association with the VAM fungus had significantly greater subleaflet P concentrations at 41 DAP, and significantly greater leaf areas, and dry weights of leaves, stems, and roots at harvest. Mamane was highly dependent on the VAM association for maximum growth, while koa was moderately dependent on the VAM association. These results dem onstrate that P uptake and early growth of mamane and koa can be incre ased significantly at low soil P levels by inoculating seedlings with an effective VAM fungus. Future research needs to demonstrate continui ng positive growth benefits of VAM fungal inoculation after transplant ing from the nursery to field conditions.