Most of the following information was gleaned from the 1991 Proceedings of the Illinois Small Fruit and Strawberry Schools and the North American Bramble Growers Association meeting in St. Petersburg. We thought a quick review would be worthwhile.
Tissue culture (TC) is a system whereby small portions of a plant, normally buds, are grown on an artificial medium. Most tissue cultures are grown in glass or plastic containers, hence, the process is referred to as in vitro (“vitro” is a Greek word that means glass). When grown in vitro, plant parts can be induced to grow as unorganized masses of cells (callus), to continue to develop shoots and/or roots. The type of development that occurs is primarily a function of the components of the TC medium. Components of the medium include sugar, hormones, vitamins, minerals, and water. Agar is usually added to thicken the solution for support of the tissue in the container. The cultures must be established and grown in hospital-like sterile (aseptic) conditions. Ahrens Nursery has reported that an operating room nurse helped them to obtain these conditions (Wengard, 1990).
When growing points are placed on the correct medium, the dormant axillary buds will elongate to form several side shoots. As these shoots develop, they can be cut from the mother culture and either transferred (subcultured) to fresh propagation medium to make more plants or rooted to make a whole plant.
In general, after rooting, TC plants are further grown in plugs in a shaded greenhouse with high humidity and/or fogging facilities. The plants will be grown in these conditions until they are large enough to be transplanted, sold directly, matured in a nursery, or placed in cold storage. Some nurseries overwinter their plants in a greenhouse and begin to deliver the plants as soon as possible in the spring. TC plants are small, light weight, and easy to ship in cartons.
TC-propagated small fruit plants are now being sold directly to the public. These plants become established quickly and grow more rapidly than traditionally propagated plants.
Receiving TC plants: Upon receipt, open the cartons immediately, especially if in midsummer. Keep the root mass and growing medium cool and moist at all times. Plant as soon as possible. Cloudy days, just before rain, or late afternoon and evenings are always the preferred times to transplant. It also may be necessary to plant after danger of hard frost has passed.
Reprinted from NASGA Newsletter 16(1) 1991 p 23