EFFECT OF COMBINED GROWTH REGULATORS ON In vitro MULTIPLICATION OF RECALCITRANT POTATO VARIETIES

The potato varieties studied in this paper were created at the National Institute of Research and Development for Potato and Sugar Beet Brasov. They have a high biological production capacity and are attractive and very appreciated by farmers, potato producers, consumers and processors, but manifest recalcitrance to the in vitro culture techniques. Thus we tried to find an optimal culture medium variant for these varieties, in order to obtain healty potato seed material in a short time. The study compared the effects of five different culture media using MS medium containing various concentrations of gibberelic acid (GA(3)) in combination with alpha-naphthalene acetic acid (NAA) in micropropagation of two recalcitrant potato varieties, Marvis and Brasovia. The longest shoots, maximum number of nodes and leaves, the longest roots and the best rooting efficiency were recorded on MS medium containing 2 mgL(-1) GA(3) and 1 mgL(-1) NAA, for both varieties. The use of a larger quantity of GA(3) negatively influenced the potato shoots and roots growth. The culture media using MS medium containing 4 mgL(-1) GA(3) and 1 mgL(-1) NAA had an inhibitory effect on all the studied plantlet characteristics. The results showed that a certain combination of growth regulators (NAA and GA(3)) improved the micropropagation capacity of the two recalcitrant potato cultivars studied and resulted in the maximum improvement in the parameters.