Micropropagation of peach rootstocks and cultivars.

There was a big demand by Hungarian peach growers on nurseries to use clonal rootstocks for the planting material production. Although 'GF 677' (Prunus amygdalus × Prunus persica) is one of the most successful and widely used clonal rootstock for peach in Europe, it is quite sensitive to low temperatures in Hungarian nurseries during winter. This was the reason for the breeding of new interspecific hybrid rootstock cultivars: 'Cadaman' and 'PeDa' (Prunus persica × Prunus davidiana) as well 'PeMa' (Prunus persica × Prunus amygdalus). These cultivars are perfectly suited for the Hungarian climate and soil types. Meantime the cultivar 'Cadaman' became a Hungarian-French common patented variety. As the origin and demand of the only cultivars have big differences, so as the danger of the viral infection under orchard conditions is large, development of the in vitro propagation procedure was necessary. Phytosanitary reasons have great pretensions to work out the micropropagation method for peach cultivars as the basis of in vitro virus elimination processes. The three-step procedure was successful for the micropropagation of peach cultivars and rootstocks. Large differences were found in the nutrient demand of the rooting phase. Following a nice growth during the multiplication and elongation phases, difficulties were arisen during the rooting phase. In spite of the high percentage of rooting, widespread shoot tip necrosis was detected. Optimal levels of the different macroelements, iron and sugar were determined in series of experiments for the clonal rootstock cultivars. The in vitro rooted plants could be successfully acclimatized under greenhouse conditions.