2017 ASHS Annual Conference

Oidiodendron mainus strains have been reported to improve the growth of Rhododendron fortunei and blueberry plants. In this study, a total of 16 mycorrhizal culture types were isolated from in vitro cultured R. fortunei seedlings. Morphological and internal transcribed spacer (ITS) rDNA analysis suggested that these isolates belong to either O. mainus or Hymenoscyphus ericae. To assess their potentials for improving plant growth, two isolates, ZO-24 and ZT-13, along with a previously identified strain Om19 were evaluated for in vitro growth of Vaccinium corymbosum ‘Sunshine Blue’. Uniform microcuttings of ‘Sunshine Blue’ derived from tissue culture were rooted in a sterile peat-based substrate in Magenta vessels. The substrate was composed of Canadian sphagnum peat and coarse sand in a 2 to1 ratio by volume and moistened with a 100 mg L^-1 N solution of Peters 20-20-20 General Purpose Fertilizer (20%N-20%P₂O₅-20%K₂O). The substrate pH was adjusted to 5.2. Three isolates were inoculated into the substrate adjacent to each microcutting, and those without inoculation were considered the control treatment. Plants were grown in a culture room for up to six months. Results showed that the mean root length, leaf number, and shoot height of plants inoculated with ZT-13 decreased compared to control plants. However, mean root numbers of Om19 and ZO-24 were 3.78 and 11.18 respectively compared to 2.83 of the control plants. Total root lengths of plants inoculated with Om19 and ZO-24 were over 5 and 37 times greater than control plants. Leaf numbers were 40% and 137% more, and shoot heights were 33% and 268% greater for plants inoculated with Om19 and ZO-24, respectively compared to the control plants. These results suggest that ZO-24 substantially improves the growth of the tested blueberry cultivar in vitro. Greenhouse and field experiments will be carried out to confirm the in vitro results.