In vitro plant regeneration of Mexican lime and mandarin by direct organogenesis

Abstract

An efficient system for in vitro regeneration by organogenesis starting from internodal stem segments from seedlings of Mexican lime (Citrus aurantifolia Christm. Swing.) and mandarin (C. reticulata Blanco cv. Monica) was developed. The best results were obtained when the wounded edges of internodal stem segments cut longitudinally were placed downward on the surface of the culture medium. The optimal culture medium from both species was Murashige and Skoog with vitamins from B5 medium, 5% sucrose, 33.3 μM BA and 5.4 μM NAA. The best response was obtained when the segments were incubated at 25 ± 2°C for 21 d in darkness, followed by 29 d on a 16/8-h light/dark cycle (fluorescent light, 54 μmol · m-2 · s-1). The best regeneration system tested allowed the attainment of adventitious shoots from 96% and 88% of the explants in Mexican lime and mandarin, respectively. In Mexican lime an average of 7.8 well-differentiated shoots per explant was obtained, and in mandarin the yield was 5.1. Rooting of 70% of the shoots was achieved in culture medium with NAA (2.7-5.4 μM) or IBA (2.5-.4.9 μM). Of the rooted plants, 85% adapted well to soil conditions. Chemical names used: 6-benzylaminopurine (BA), α-naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA).