Studies on Carob (Ceratonia siliqua L.) Propagation

Abstract

Carob (Ceratonia siliqua L.) is an environmentally and economically important tree and is among the most difficult to propagate fruit species. In this study, efforts were made to propagate the plant by using three different methods; seeds germination, cuttings and micropropagation. Seeds and cuttings were scarified and disinfected under aseptic conditions to improve the germination percentage and the percentage of success of cuttings in April and September through two successive seasons (2011 and 2012). Results showed that the highest values of seed germination percentage, the fastest germination, the greatest plant length, number of leaves/plant, root length and dry weight were obtained by soaking seeds in 60% H2SO4 in April and September through the two seasons, but there was no significant difference between the first and the second date in both studied seasons for most of the studied parameters. April was found the best time for propagation of Carob by cuttings, for all treatments. Besides, carob cuttings treated with indole-3-butyric acid (IBA) at 8000 mg/l + β- naphthalene acetic acid )NAA( at 200 mg/l gave the highest values of parameters (shoot length, no. of lateral shoot, no. of leaves/plant, root length, no. of roots/plant and root dry weight) followed by IBA at 6000 mg/l + NAA at 200 mg/l, in both seasons. While, all cuttings failed to root for all treatments in September, except when they were treated with IBA at 6000 mg/l + NAA at 200 mg/l and IBA at 8000 mg/l + NAA at 200 mg/l, in the two studied seasons. Micropropagation of carob was developed by using shoot tips and stem node segments, of ex vitro grown seedlings, as explants. Hundred % of growth induction was obtained, for both explants, with the highest number of shoots on Murashige and Skoog (MS) medium containing 0.4 mg/l NAA + 2 mg/l 6- benzylaminopurine (BAP). Shoots were best multiplied on MS medium containing BAP (1.0 mg/l), while the media containing N6-(2-isopentenyl) adenine (2iP) gave the highest lengths of shoots (2iP at 1.0 mg/l). For further elongation and multiplication of shoots, the combination of both BAP and 2iP gave promising results at concentrations of 0.5 mg/l BAP + 0.5 mg/l 2iP or 1.0 mg/l BAP + 0.5 mg/l 2iP. Attempts to achieve rooting were unsuccessful, since only shoot development was observed.