effects of soil sterilization, mycorrhizal inoculation, and rates of phosphorus on growth and survival of Kalopanax septemlobus microplants during the acclimatization period

In order to establish some cultural practices that can improve growth and survival of somatic embryo (SE)-derived microplants during the acclimatization period, Kalopanax septemlobus was uninoculated or inoculated with mycorrhizal fungi coded as AMM6 (a mixture of unidentified species of Glomus and Acaulospora collected in a closed mine tailing site in Bonghwa, Korea) during ex vitro and grown in oven-sterilized peat vermiculite medium. After 2 months, treated microplants were transferred into pots filled with the same medium amended with phosphorus fertilizer {0, 2, 4, 8, 16 and 32 mg P [as Ca(H₂PO₄)₂·H₂O] kg medium⁻¹ coded as P0, P2, P4, P8, P16 and P32, respectively}. At this stage, inoculated plants were greener, with broader leaves and well-developed root systems and had higher survival than the uninoculated ones. After 6 months, inoculated plants were 54 % heavier than the uninoculated counterpart. In sterile medium, total dry weight of uninoculated plants was promoted at P8 and highest at P16. Total dry weight at P16 by uninoculated plants was attained at P4 by the mycorrhiza-inoculated counterpart. In non-sterile medium, total dry weight of inoculated plants was increased at P8. By contrast, uninoculated plants did not respond to the applied P rates. In conclusion, more SE-derived microplants survived and grew better in sterile medium. Maximum benefits from AMM6 was attained with applied 4 and 8 mg P kg medium⁻¹ (P4–P8) in sterile and non-sterile medium, respectively.