Micropropagation is a plant multiplication technique very popular in Italy, especially in the fruit sector. Nonetheless, even though the country is renowned in Europe for the quantity and quality of the plants produced, it still has to face competition from Eastern European countries. 

Researchers from the Plant Physiology and Biochemistry at the Agricultural University in Plovdiv, Bulgaria, assessed the effect of meta-Topolin (MT), an aromatic natural cytokinin, on the micropropagation of pear rootstock OHF-333 (Pyrus сommunis L.). 

Clone OHF-333 is a rootstock part of the US OHF series, which are obtained by the Old Home x Farmingdale crossbreed. It has good compatibility with most cultivars, high yields and a moderate resistance to fire blight. 

Micropropagated cultures were incubated in a growth chamber at 22±2°С and 16/8 hours of photoperiod. The in vitro culture was maintained on a Murashige and Skoog medium supplemented with various concentrations of meta-Topolin (0, 3, 6, 9 or 12 micromoles). After three weeks, growth parameters and physiological and biochemical aspects were assessed. 

It emerged that the absence of meta-Topolin does not provide a practical solution for an efficient multiplication of pear rootstocks.

In vitro multiplication of pear rootstocks OHF-333 on a medium supplemented with various concentrations of meta-Topolin (mT).

A good multiplication rate and high-quality shoots were observed on plants grown with 6 and 9 mT micromoles, as they improved leaf gas exchange.

"This study confirmed that a concentration of 6 and 9 meta-Topolin micromoles is excellent to obtain an in vitro multiplication of rootstock OHF-333. In general, cytokinin mT could be used for the micropropagation of other pear genotypes, especially in case of rooting problems."

Source: Natalya Dimitrova, Lilyana Nacheva, Małgorzata Berova, 'Effect of meta-topolin on the shoot multiplication of pear rootstock OHF-333 (Pyrus communis L.)', 2016, Acta Scientiarum Polonorum - Hortorum Cultus, Vol. 15(2), pag. 43-53