MICROPROPAGATION OF DATE PALM (PHOENIX DACTYLIFERA L.) SELECTED GENOTYPES FROM INFLORESCENCE TISSUES BY USING SOMATIC EMBRYOGENESIS TECHNIQUE

Research activities on date palm micropropagation have permitted to multiply a great number of known cultivars worldwide. However, micropropagation of some important rare or selected date palm genotypes is still hampered by the lack of offshoots. To overcome this problem, the use of tissues excised from inflorescences, at their emergence, has permitted to succeed in micro-propagation of many selected genotypes by using the organogenesis technique. However, some selected genotypes are still recalcitrant and it is very difficult to regenerate vegetative buds directly from cultured explants. In order to adapt this technique to such recalcitrant genotypes, the embryogenesis technique was tested to succeed in their multiplication. Three different auxins (2,4-D, Picloram and Dicamba) were tested on callus initiation from inflorescence tissues of a selected date palm genotype INRA-D12. Embryogenic callus was obtained on medium containing 12 mg L^-1 of Dicamba, 2 mg L^-1 of BA and 300 mg L^-1 of activated charcoal. Obtained callus was multiplied on culture media devoid of 2,4-D and activated charcoal. After 4 multiplication cycles, a mixture of somatic embryos and vegetative buds were regenerated. Obtained buds were successfully multiplied and complete plantlets were regenerated. Vegetative buds were similar, both in terms of multiplication rate and behaviour, to those obtained directly from explants excised from date palm shoot tips. Produced plantlets were successfully acclimatized in a greenhouse and are now ready to be transferred to soil for field evaluation. Some vitro-plants will also be reserved for Bayoud resistance tests. In the present protocol, a relatively low auxin concentration and a limited number of callus multiplication cycles were used and this will be more secure concerning true-to-typeness of regenerants.