Micropropagation of wild pear species of Fars province

Fars province is one of the natural habitats of Pyrus species inIran. Harvesting of fruits, deforestation, expansion of agriculture and overgrazing in recent years has threatened the wild pear forests and imposed detrimental effects on their natural regeneration, therefore, investigation on propagation of wild pear species for afforestations is needed. This research was carried out to develop tissue culture techniques for rapid and mass propagation of wild pear species native to Fars province. Several trees of wild pear species including Pyrus glabra Boiss. Pyrus syriaca Boiss. and probably natural hybrid of mentioned species (P. glabra × P. syriaca) were selected in Deh-Kohne forest in Sepidan County, Fars province, Iran. Seeds and current season growth shoots of selected trees were used as explants. Surface disinfection of plant materials was performed with immersion in 70% ethylic alcohol for 1 minute, commercial bleach Bojne (5% available chlorine) 2-5 % for 15 minutes and rinsed three times with sterile distilled water. Nodal segments with 3-4 axillary buds free of contamination were established on MS medium containing 0.4- 1.0 8 mgl-1 BA, 30 gl-1 sucrose and solidified with 8.0 gl-1 Difco Bacto agar. Concentration of 0.8 or 1.0 mgl-1 BA and 0.01 mgl-1 IBA or NAA was optimum for shoot multiplication. Explants cultured on media containing sucrose or glucose did not show any significant differences for shoot fresh weight, callus fresh weight, number of shoots and main shoot length, but both of them was significantly better than those cultured on media containing fructose. Media solidified with Phytagel were significantly better than those solidified with Difco Bacto agar for shoot fresh weight. The best procedure for rooting of in vitro produced shoots consisted of two phases: in vitro root induction and ex vitro root development. For root induction, Pyrus glabra shoots were cultured on MS medium (half strength macronutrients) containing 50 mgl-1 IBA and incubated in dark conditions for 24 hours. For root development, shoots were transferred from root induction medium, washed with tap water, planted in moistened Jiffy-7 pots, sprayed with 1.0 gl-1 Benomyl solution and placed in a propagator with 90-95% relative humidity in lighted conditions. Using this method 100 percentage of shoots rooted and plantlets were successfully transferred to larger pots. Pyrus syriaca shoots were also cultured on DKW medium (half strength macronutrients) containing different concentrations of IBA and incubated in dark conditions for 24 hours. For root development, shoots were transferred from root induction medium and planted in moistened Jiffy-7 pots. One hundred percentages of shoots cultured on media containing 75 mgl-1 IBA after transfer to Jiffy-7 pots rooted. Rooting percentage of natural hybrid of wild pear (P. glabra×P. syriaca) shoots on DKW medium with half strength macronutrients was significantly higher than that of full strength DKW medium. Inclusion of 0.1 mgl-1 BA in nutrient media had negative effects on rooting of Pyrus syriaca shoots and significantly decreased rooting percentage.