Clonal Propagation of Carob (ceratonia Siliqua L., Fabaceae)

Mature seeds of carob tree (Ceratonia siliqua L.) were germinated on hormone free MS medium. Efforts were made to develop multiple shoots by using axillary buds of in vitro grown seedlings on MS medium fortified with different concentrations of BA singly and BA in combination with IAA or GA3. Axillary buds produced single shoot with a moderate amount of callus at the base of the explant after culturing on MS medium with BA alone. Multiple shoots were regenerated when explants when cultured on MS medium fortified with BA + IAA or BA + GA3. MS medium supplemented with 1.5 mg/l BA + 0.5 mg/l GA3 was found more effective in multiple shoot regeneration than all other combinations. Regenerated multiple shoots were excised and cultured on half strength of MS medium containing different concentrations of IBA for root induction. Best root development was obtained in half strength MS medium containing 0.5 mg/l IBA. About 70% of the regenerated plantlets survived in natural conditions. Introduction The carob tree, Ceratonia siliqua L. (Fabaceae), has been grown since antiquity in most countries of the Mediterranean basin, usually in mild and dry places with poor soils. Its value was recognized by the ancient Greeks who brought it from its native Middle East to Greece and Italy, and by the Arabs, who disseminated it along the North African coast and north into Spain and Portugal. The carob tree grows as a sclerophyllous evergreen shrub or tree up to 10 m high, with a broad semispherical crown and a thick trunk with brown rough bark and sturdy branches. Carob pods are used as fodder for ruminants (Louca and Papas 1973) and non-ruminants (Sahle et al. 1992).The seed of the carob tree contains galactomannon, a commercially valuable carbohydrate that is used as thickener, emulsifier and stabilizer in many commercial products (Lewington 1990). Wood is reported to be used in making furniture and carts. Commercial production of carob pods is estimated currently to be about 310,000 tons per year. Conventionally carob plants are propagated by seeds. Dried, hard seeds need to be scarified or chipped and then soaked in water or dilute sulfuric or hydrochloric acid solutions until they swell. Germination rate may be only 25%. Seeds usually germinate after six weeks or more. Budding of this plant is done when the stem is at least 1 cm thick. Some common pests, insects (viz. the carob moth, Myelois ceratoniae) and fungi are main obstructions for the conventional propagation of this plant. It lays eggs on the flowers or newly-formed pods and the larvae bore into the pods and damage them. The larvae of a midge, Asphondylia gennadii, cause stunting of pods. Application of tissue culture method offers rapid multiplication of forest, fruit as well as other crops specially those which are heterozygous and difficult to propagate by conventional means (Litz et al. 1983, McCown and McCown 1987, Ahuja 1991). It has already been established that micropropagation of shoots has become an important method for multiplication of fruit trees (Krieken et al. 1993). Moreover, micro shoots obtained by this method could be the material source for studying the morphogenetic capacity of different organs and tissues, appearance of somaclonal variants (Besendorfer et al. 1989) and resistance to pests or diseases.