Effect of phytohormones on in vitro shoot multiplication and rooting of lime Citrus aurantifolia (Christm.) Swing

Multiple shoots were produced from node explants of lime (Citrus aurantifolia (Christm.) Swing) on MS medium supplemented with 6-benzylaminopurine (BAP), 6-furfurylaminopurine (kinetin) and alpha-naphthaleneacetic acid (NAA). The highest number of shoots, nine shoots per node, were produced on a medium containing 2 mg l(-1) BAP (8.8 muM), 1 mg l(-1) kinetin (4.6 muM) and 1 mg l(-1) NAA (5.4 muM). Depending on the concentration of BAP and kinetin, NAA either inhibited, stimulated or did not affect shoot multiplication, which also depended on the cytokinin level. Maximum shoot length was obtained from treatments containing 0.5 mg l(1)(-) BAP (2.2 muM) combined with I mg l(-1) kinetin (4.6 muM) and 0.5 mg l(-1) NAA (2.7 muM). The largest leaves of resultant shoots were produced on a medium containing 0.5 mg l(-1) each of kinetin (2.3 muM) and NAA (2.7 muM). Transferring in vitro shoots to rooting media containing indole-3-butyric acid (IBA) and NAA produced complete plantlets. The highest rooting percentage was obtained on a medium containing either 1 mg l(-1) NAA (5.4 muM) alone or 0.5 mg l(-1) NAA (2.7 muM) combined with 2 mg l(-1) IBA (9.6 muM), whereas the highest number of roots were produced on a treatment containing both 2 mg l(-1) NAA (10.8 muM) and 2 mg l(-1) IBA (9.6 muM). Roots elongated most on treatments containing 0.5 mg l(-1) of either NAA (2.7 muM) or IBA (2.4 muM). Shoot growth associated with the rooting phase was the highest in response to 2 mg l(-1) IBA (9.6 muM) or 0.5 mg l(-1) NAA (2.7 muM). Plantlets that survived acclimatization, 82%, exhibited normal growth in soil under greenhouse conditions. (C) 2002 Elsevier Science B.V. All rights reserved.