Cider is an important cultivated tree and one of the few truly native tree species of Saudi Arabia that is still growing along with many newly introduced exotic plants. The present study describes the influence of inorganic and organic media constituents on micropropagation of the Noaf variety, Ziziphus spina-christi. Shoot apices of 0.5 -1.0 cm were cut and transferred to a basal tested nutrient medium. The full concentration of M & S in this study yielded the best results in shoot length (3.02 cm) and number of leaves (1.80). No bud growth was observed in media devoid of sucrose. Shoot length, number of nodes and number of leaves were improved steadily with the addition of sucrose up to the concentration of 3.0% which showed a significant increase in all studied growth parameters. The full concentration of White's organics (1X), gave a significant increase in the shoot length (1.6cm) and number of nodes (2.4) over all other treatments. The bud growth of Cidir showed little response to the inositol treatment, since no significant difference in shoot length was observed between the control treatment (no inositol) and 1000 mg/L. The best adenine sulphate concentration that gave the best enhancment in most growth parameters was 80 mg/L. Shoot length (5.56 cm), number of nodes (6.7) and number of leaves (3.2) were enhanced by 1 mg/L charcoal concentration. This treatment was not significantly different from 2 mg/L treatment in shoot length and number of nodes although the 1 mg/L treatment showed a noticeable increase in these two parameters. Tissue culture application to the clonal propagation of "Cidir" will allow for the elimination of diseases and the rapid clonal production in large numbers of genetically identical plant material. The technique also greatly enhances the introduction of this variety (Noaf) and stimulates interest among nurserymen in Cidir cultivation as a fruit tree. Establishment of an in Mohammed A. Al-Sulaiman 4 vitro propagation scheme would enhance cloning of "Cidir", since propagules for future propagation can be derived from plantlets growing in vitro, and circumventing the requirements for explants from this sole stock plant available.

This investigation was conducted to establish a reliable in vitro plant regeneration system, which is a prerequisite step before conducting any genetic manipulation system. Five different potato cultivars (Daraga, Sponta, Diamont, Cillan and Burun) with two explants and four medium protocols were used in this study to find out the best cultivar of potato linked with the optimum medium conditions for callus induction; and subsequently plant regeneration. The results indicated that all in vitro traits were highly significant influenced by differences in potato cultivars, explants, and medium protocols, as well as for the interaction between the three different factors, except for the interaction between explants and medium protocols for callus induction and callus weight, which showed no significant difference. Also, the callus weight was not significantly different due to medium protocols. The shoot formation derived from callus of nodal explants produced the highest percentage of shoot formation (20.7%) across the cultivars, which was significantly different from the shoot formation derived from callus of leaf explants (6.5%). Results also revealed that there was a highly significant interaction between the cultivars and explants, for instance, the Daraga cultivar produced high percentage of shoot formation derived from callus of nodal explants (40.5), while the percentage of shoot formation derived from callus of leaf explants was (7.9%). Results showed that the medium protocol "3" produced the highest percentage of shoot formation (23.9%) across the potato cultivars, which was significantly different from other medium protocols. Results also revealed that there was a highly significant interaction between the cultivar and medium protocol. The Daraga cultivar produced the highest percentage of shoot formation (51.2%) on medium protocol "3", which was significantly different from the other protocols. Results showed that there was a highly significant difference between medium protocols and explants. The highest 4 Mohammed Abdulaziz Al-Sulaiman percentage of shoot formation was obtained with callus derived from nodal explants (38%) on medium protocol "3". However, the percentage of shoot formation derived from callus of leaf explant on the same medium protocol was (10%).

In vitro shoot multiplications were obtained successfully from shoot tips of Ziziphus spina-christi by placing explants into solidified medium (MS medium) supplemented with 0.01 mg/l NAA and 0.1 mg/l BA or 0.1 mg/l IAA and 1.0 mg/l kinetin. It was concluded that lower concentrations of all cytokinin studied were better for lateral bud proliferation and that BA and 2IP were better than kinetin in the production of lateral branches. No growth regulators were required for shoot growth and elongation. The shoots rooted best on MS medium supplemented with 1.0 mg/l IBA. Plantlet survival after transfer to soil was more than 90%. The shoot proliferation method described could be used for the mass clonal propagation of selected genotype cv Noaf variety. The variety is in a great demand due to its attractive fruit characteristics such as flavour, sweetness and fruit yield.