FACTORS AFFECTING IN VITRO PROPAGATION AND MICROGRAFTING OF SOUR ORANGE CITRUS ROOTSTOCK

The present investigation was aimed to address two important questions:
1- To what extent is tissue culture can be succeeded in sprouting and rooting the Sour orange?
2- How did the activities of media studied respond to such processes?
The possible application of some commonly in vitro growth regulating compounds is outlined. A number of treatments were applied to determine the best way of inducing in vitro shoot proliferation and rooting on a modified solid MS (1962) medium at full strength. Two explants type (shoot tips and epicotyls) sourced from Sour orange (Citrus aurantium L.) Citrus rootstock were cultured for in vitro shoot proliferation and the regenerated shoots for rooting studies. The former process tested the effect of 6-benzylaminopurine (BAP) and 6-furfuryl aminopurine(Kinetin) either alone or in combinations at different concentrations plus a fixed 0.50mg|l NAA. While, the later process tested the effect of combined two auxins, indole-3-butyric acid (IBA) and alpha- naphthaline acetic acid (NAA) at varying concentrations plus a fixed 0.50mg/L Kin.
The obtained results pointed to epicotyls as the better explants to in vitro propagation of the tested rootstock. Medium to best shoot proliferation was MS(1962)basal medium at full strength supplemented with BAP at 1.5mg/L and Kin at 1.00mg/L plus a fixed NAA concentration. Both explants type on this super medium gave a high percentage of shoot multiplication and proliferated shoot of the greatest characteristics except for average shoot length per explant, which the longest shoots were resulted on the same basal medium with the combined two growth regulators at lower concentration (0.25 or 0.50mg/L). Medium to best in vitro rooting was the same basal medium containing IBA and NAA at 2.00mg/L each plus a fixed 0.50 mg Kin/L. The egenerated shoots on such rooting medium succeeded to record the highest rooting percentage, average roots number per explant and the longest proliferated roots as well as relatively the biggest average root diameter per explant.
Micro-grafting study of Washington navel and Valencia scions onto Sour orange rootstock indicated a successful graft union. Micro-graft combination of the former scion onto such rootstock had a degree of graft compatibility greater than Valencia scion onto the same rootstock. This was based on the measurement of three important parameters in this field,  grafting success % , survival % and the whole growth vigor of grafted seedlings through the measurement of three characteristics on the grafted seedlings.