Plant Tissue Cult. 11(1) : 15-23, 2001(June)

Growth Responses and Physiological disorders in Wild Pear (Pyrus syriaca Boiss.) During Slow-growth In vitro Preservation on Osmostressing Media

Riham W. Tahtamouni, Rida A. Shibli¹ and Mohammed M. Ajlouni

Biotechnology Center, Jordan University of Science and Technology, Irbid, Jordan.
E-mail: shibli@just.edu.jo

Key words: Growth response, Physiologyical disorders, In vitro, Preservation, Pyrus

Abastract

Growth and behaviour of wild pear (Pyrus syriaca Boiss.) were studied during in vitro preservation on osmostressing MS medium. Microshoots (1.0 cm) with tips were preserved on media containing 3, 6, 9 or 12% of either sucrose, sorbitol or mannitol. Growth was severely reduced with an increase of osmoticum concentration. There was an escalation of physiological disorders (shoot tip browning, stem basal-end browning, and leaf-loss) with an increase of elevated osmostressing and as preservation period was extended. All preserved microshoots survived till the end of the preservation period (12 weeks). Nodal segments (1.0 cm) were very unsatisfactory for in vitro preservation. Regrowth percentage of microshoots were higher compared to those obtained by nodal segments regardless of the osmostressing treatment. Generally, the performance of microshoots in terms of growth, quality and survival rate was better than that of nodal segments during and after preservation on osmostressing media. Among the tested osmostressing agents, sucrose (at lower concentrations) was the most suitable to reduce physiological disorders and for higher regrowth. Preservation under dark conditions was very ineffective, and a maximum of 20% survival at 3% sucrose was obtained and none of the surviving microshoots or nodal segments were able to regrow when subcultured to the fresh medium.

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