SPECIAL-WORKSHOP DESIGNING A MICROPROPAGATION SYSTEM: WORKSHOP PRESENTATIONS FROM THE 1998 SIVB CONGRESS ON IN VITRO BIOLOGY

Development of a micropropagation system for a new species or cultivar can be a daunting task and hundreds of decisions are involved in even deciding where to start. Dozens of basal media, growth regulators, and supplemental nutrients are available for use. Environmental conditions to be considered include light intensity and quality, photoperiod, temperature, container, amount of medium, liquid vs. semisolid, gelling agent, and container closure. This workshop was designed to assist micropropagators in determining directions to take and general tissue culture procedures to use when initiating culture of a new genotype. These contributions are from researchers with substantial backgrounds and experience in micropropagation of recalcitrant or challenging plant types and have provided some key insights into the steps taken to successfully adapt the plants into continuous micropropagation systems. First, McCown outlines a general protocol of steps to consider in implementing commercial micropropagation of specific plant types. He introduces a 'decision tool' approach to take when considering whether or not to tackle the commercial micropropagation of a new plant with no previous history in culture. As he explains, the growth characteristics a plant typically has in nature can make an enormous difference in the ease with which it can be adapted to plant microculture. Skirvin outlines a series of interconnected strategies aimed at improving success in establishing contaminant-free plants in culture. He discusses pretreatment and growth conditions of source plants which may minimize contaminants, selection of explant pieces, disinfestation procedures, and improving sterile technique during transfer. He discusses basic procedures and plant characteristics to consider during the explant stage. Smith introduces the particular challenges of bulb crop culture. She describes the rationale for why in vitro strategies are particularly useful for the bulbs of Hippeastrum and Zephranthes which are difficult to propagate by conventional means. The most compelling challenge to the introduction of explants in vitro is the successful disinfestation of the bulbs, which due to their growth underground are difficult to surface disinfest. Smith describes a twin-bulb scaling technique that has proven particularly useful for these species, and compares a series of disinfestation tactics (gleaned from the literature and internet tissue culture list-serve discussions) to determine the most efficient approach to explant preparation. Mackay's contribution deals with a specific group of plants that are also quite challenging to micropropagate, but for unique reasons. The native species of the Chihuahuan desert are adapted to low rainfall, and due to the erratic conditions in their native habitat, are not routinely available for explant collection every yr. When they are available, the window of opportunity for collecting explants in correct physiological status is quite narrow. This group of native species is also characterized by problems with excessive exudates and is particularly difficult to acclimatize to ex vitro conditions. Mackay describes a series of procedural steps taken to successfully adapt the plant materials to in vitro culture and subsequently to make them available for use as adaptable native landscape plants for the region. Barbara M. Reed Mary Ann Lila Smith