PRODUCTION AND ACCLIMATIZATION OF IN VITRO PRODUCED STRAWBERRY PLANTS

In vitro propagated plants were transferred to a soil medium and acclimatized to environmental conditions in a greenhouse provided with a misting system. The in vitro cultures used in the experiments were initiated from isolated shoot apical meristems from young, fully developed runners of selected healthy strawberry plants. Explants, 0.2 to 0.4 mm long, were dissected with the aid of a stereomicroscope, placed onto an induction culture medium and incubated under light and temperature controlled environmental conditions (25°C and 16 h light photoperiod in a growth chamber). Induced cultures were transferred at four to five week intervals to a multiplication medium, where they grew as clusters of multiple shoots. To produce complete plants, individualized shoots were transferred to a rooting medium and maintained there for three to four weeks, until roots were well developed. Rooted micropropagated plants were washed with distilled water to eliminate the culture medium, and transplanted into plastic trays containing Sunshine Mix3 (Sun Gro Horticulture Canada Ltd.). These plants were maintained in a greenhouse, applying water mistings for five minutes at 20 minutes intervals, to keep a high relative humidity (above 80 %). This is the most critical step in the acclimatization process, since plants coming from in vitro cultures are very susceptible to dehydration when they are exposed to environmental conditions. These plants were maintained in the greenhouse for three to five weeks for hardening and then transferred to disinfested soil in a nursery for the production of runners. A second generation of plants was propagated in soil once more in the nursery. These plants were used to establish the strawberry production fields in the Irapuato region in the Guanajuato state of Mexico.