Substitution of benzyladenine with meta-topolin during shoot multiplication increases acclimatization of difficult- and easy-to-acclimatize sea oats (Uniola paniculata L.) genotypes

Benzyladenine (BA) is the only cytokinin to effectively induce shoot multiplication in vitro between genotypes of the important dune grass species Uniola paniculata (sea oats). However, a significant genotype-specific negative carryover effect of BA on ex vitro acclimatization has been observed. In the present study, the effects of multiplication media supplemented with meta-topolin (mT), a BA-analog, BA or no plant growth regulator, were compared on in vitro multiplication, rooting and ex vitro acclimatization using easy- and difficult-to-acclimatize sea oats genotypes. Both genotypes exhibited similar in vitro shoot dry weight, number of harvestable shoots and percent rooting when cultured under standard conditions (with 2.2 mu M BA) or with an equimolar concentration of mT. In addition, both genotypes exhibited similar ex vitro leaf length and shoot production under these two culture conditions. However, ex vitro acclimatization of rooted microcuttings of the difficult-to-acclimatize genotype significantly increased when produced on shoot multiplication medium containing mT rather than BA. Meta-topolin concentrations 10 mu M or greater were inhibitory to in vitro rooting and acclimatization ex vitro of both genotypes. Nevertheless, survival of the difficult-to-acclimatize genotype was significantly greater when cultured in the presence of 2.2 mu M-30 mu M mT, compared to 2.2 mu M BA. Therefore, a potential solution to overcome the detrimental BA carryover effect on ex vitro survival in sea oats is the substitution of BA with 2.2 mu M mT for Stage II shoot multiplication. Use of mT may provide an efficient method to ensure in vitro propagation of a large number of diverse sea oats genotypes for dune restoration.