In vitro regeneration of Citrus hystrix DC

An efficient plantlet regeneration system for Citrus hystrix DC has been developed in this study. N-6-benzyladenine (BA) was most commonly used plant growth regulator in micropropagation of Citrus spp. However, our study demonstrated that BA alone was insufficient to induce normal in vitro shoot regeneration of C. hystrix due to the occurrence of leaf senescence on the regenerated shoots. The inclusion of silver nitrate (AgNO3) at 10.0 mu M into Murashige and Skoog (MS) medium containing 2.22 mu M BA could effectively overcome the leaf senescence and improved shoot regeneration from different explants (cotyledonary node, cotyledon, hypocotyl and primary root) of C. hystrix. In the rooting experiment, the application of continuous indole-3-butyric acid (IBA) and naphthaleneacetic acid (NAA) treatment of 4.92, 9.84, 14.76, and 19.69 mu M IBA or 1.34, 2.69, and 5.37 mu M NAA in combination with 20.0 mu M AgNO3 resulted in poor rooting of C. hystrix shoots. Rooting was significantly improved upon exposure of shoots to IBA pulse treatment of 9,840 mu M for 16 h prior to their transfer on MS medium supplemented with 20.0 mu M AgNO3. Assessment of various potting mixtures for acclimatization showed medium containing loamy soil: Peatgro: sand (1:1:1; v/v/v) produced high percentage (83.3 %) of plantlet survival.