Efficient propagation and rooting of three citrus rootstocks using different plant growth regulators

Abstract

The influence of various basal medium and plant growth regulators on the efficient micropropagation of nodal explants from mature trees of alemow, sour orange, and ‘Cleopatra’ mandarin citrus rootstocks was studied. All three citrus rootstock shoot cultures showed a preference for high-salt media, like Murashige and Skoog or Driver and Kuniyuki Walnut medium. Several combinations of N 6-benzyladenine (BA) and adenine (AD), kinetin (KIN) or gibberellic acid (GA) were tested to optimize the shoot proliferation phase. BA/GA combinations improved the proliferation of all the rootstocks studied, especially alemow. The addition of BA and AD to the culture medium improved shoot proliferation in sour orange and ‘Cleopatra’ mandarin in the same way as BA and GA. The addition of different combinations of BA/KIN did not result in further improvement of any of the studied variables. The transfer of in vitro shoots to rooting media, containing different concentrations of indolebutyric acid (IBA) and indoleacetic acid (IAA), resulted in regeneration of complete plantlets. Alemow and ‘Cleopatra’ mandarin shoots rooted well using these plant growth regulators; however, all combinations of IBA and IAA tested resulted in very low rooting percentages in sour orange. To improve rooting in sour orange and ‘Cleopatra’ mandarin, different combinations of naphthaleneacetic acid (NAA) and IBA were tested. All NAA/IBA combinations produced higher rooting percentages than did the IBA/IAA combinations, and in sour orange nearly 100 % of explants developed roots. An efficient and simple protocol for the micropropagation of three citrus rootstocks, alemow, ‘Cleopatra’ mandarin, and sour orange, by culturing nodes from mature plants, has been established.