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DEFINING JUVENILITY IN THE APOMICTIC SYSTEM OF MALUS HUPEHENSIS FOR BASIC STUDIES ON REGENERATION AND TRANSFORMATION

HAFEEZ UR-RAHMAN, D.J. JAMES^*, P. D. S. CALIGARI^** AND A. WETTEN^**

Abstract: The apomictic system in Malus was used as a model to examine the competence of genetically identical mature and juvenile tissues for regeneration and to undergo genetic transformation using Agrobacterium tumefaciens. Thidiazuron (TDZ) 1.00 mg l^-1 added in the regeneration media enhanced the frequency of regeneration and the mean number of shoots per explant and was found to be more effective then Benzyladenine (BA). Explants of juvenile (J) origin and those with the adaxial side (A) in contact with the medium exhibited a higher regeneration frequency and mean number of shoots regenerating per explant than explants of mature (M) origin and explants with the abaxial side (B) in contact with the medium. It was possible to obtain transgenic callus lines, and shoot organogenesis from the transformed callus using the hyper virulent strain EHA101 although M. hupehensis is reported to be resistant to crown gall disease (Sax, 1949). However, higher regeneration frequency from the J clones did not correlate with ease of transformation.

Fruit Crops, National Agricultural Research Centre (NARC), Islamabad, Pakistan

^*Horticulture Research International, East Malling, West Malling, Kent ME19 6BJ, U.K

^**Department of Agricultural Botany, The University of Reading, Whiteknigth Reading RG6 6AS, UK.