Title : New strategies in clonal micropropagation of fruit crops
Abstract:
Traditionally, clonal micropropagation of fruit crops is implemented in 5 stages: introduction to culture, bud proliferation, elongation of shoots, rooting of micrografts, and adaptation of microplants to non-sterile conditions. Many attempts have been made to modernize this well-known scheme, especially its last stages. For example, it was proposed to carry out rooting of microchips not on an agarized nutrient medium, but on a solid substrate of different composition, both under sterile conditions and non-sterile, while solving simultaneously the problem of adaptation. The greatest difficulties arise with woody fruit trees, such as, apple, pear, sweet cherry, plum, sour cherry, because these crops need a period of rest. Adapted microplants of these species can be obtained in large quantities, but special conditions and special techniques are required so that they can be transferred to open ground. These plants, as a rule, have a very inconvenient size for work (stem length is 2-5 cm) and do not survive well after transplantation. For this case, we have developed a technique of triple simulation of the rest period during a calendar year and alternating it with periods of growth. Such work is performed using the greenhouse with a temperature regime of + 18 ... + 22 0? and a refrigerating chamber with a temperature regime of + 1 ... + 6 0?. According to this strategy, without leaving the greenhouse for the calendar year, you can grow plants of sweet cherry, plum, and sour cherry to a height of 100-120 cm. For berry bushes (raspberries, blackberries, honeysuckle), as well as grapes, combining the elongation and rooting stages proved effective. Microshoots with a length of 0.5-1.0 cm were planted on a nutrient medium with a low concentration of cytokinin. 250 ml flasks were used as cultivation vessels, and micrografts were planted with 10–12 pieces each. Within 1.5 months microplants reached a height of 5-7 cm, at the same time their spontaneous rooting occurred, even in those varieties that were previously difficult to root using auxins. Mass successful adaptation of grassy plants (strawberries) was obtained using hydroponics and it was based on the natural ability of strawberries to root when in contact with a moist environment. A thin synthetic material, perforated with 3-4 mm diameter holes, was placed above the surface of the nutrient solution, which circulated in automatic mode, washing the roots. The roots of microplants were immersed in the solution through the mounting holes, leaving the plantlets themselves above the solution. Within 1 month the plants formed a strong root system, adapted to normal air humidity and maintained viability at the level of 100% when transplanted into a non-sterile soil substrate.
Take Away Notes:
• This experience will make it possible to take a fresh look at the possibilities and prospects of clonal micropropagation.
• The presented information can be used for the implementation of industrial schemes for obtaining plants by the in vitro method.
