The role of activated charcoal in plant tissue culture.

Date Palm Phoenix dactylifera L.

Under the Joint FAO/IAEA programme, radiation-induced mutations are used for genetic improvement of both seed and vegetatively propagated plants. The FAO/IAEA programme maintains a database of officially released mutant varieties worldwide (http://www-mvd.iaea.org/). Currently, over 2300 mutant varieties are registered in our database. Coordinated Research Projects (CRPs) and Technical Co-operation Projects (TCP) are two major activities at IAEA that serve Member States at the national, regional and interregional levels. This article highlights CRPs on banana, underutilized and neglected crops, and tropical and subtropical fruits. CRPs on banana and underutilized and neglected crops have already been concluded. TCPs in South East Asia (Thailand, and Malaysia), Africa (Algeria, Morocco, Tunisia, Ghana), and the Middle East (Yemen) are discussed. The main projects in South East Asia are on genetic improvement of ornamental plants, fruits and cereals. In Africa, projects are on cassava, date palm, salinity and drought. In the Middle East, funded projects are related to salinity, and drought. In this article, major achievements are highlighted through CRPs and TCPs on low cost tissue culture, banana, underutilised and neglected crops, tropical and subtropical fruits.

Major mutation-assisted plant breeding programs supported by FAO/IAEA

An improved protocol is described for the large-scale micropropagation of an elite date palm (Phoenix dactylifera L.) cultivar, Deglet Nour. Clonal plants were regenerated from somatic embryos derived from highly proliferating suspension cultures. Friable embryogenic calli were initiated from both leaf and inflorescence explants. Suspension cultures consisting of pro-embryonic masses were established from calli showing a high competency for somatic embryogenesis. The subculture of suspensions in liquid medium enriched with low amounts of plant growth regulators (1 mg l-1 2,4-dichlorophenoxyacetic acid with 300 mg l-1 charcoal) resulted in the differentiation of large numbers of somatic embryos. The productivity of the cultures increased 20-fold (from 10 to 200 embryos per month per 100 mg fresh weight of embryogenic callus) when embryogenic suspensions were used instead of standard cultures on solid media. The overall production of somatic embryos reached 10,000 units per litre per month. Partial desiccation of the mature somatic embryos, corresponding to a decrease in water content from 90% to 75%, significantly improved germination rates (from 25% to 80%). The cutting back of the cotyledonary leaf was also found to stimulate embryo germination. Flow cytometric analysis showed that the micropropagation protocol followed here did not affect the ploidy level of somatic embryo-derived plantlets.

An optimised protocol for plant regeneration from embryogenic suspension cultures of date palm, Phoenix dactylifera L., cv. Deglet Nour

Histocytological analysis of callogenesis and somatic embryogenesis from cell suspensions of date palm (Phoenix dactylifera).

During recent years, different approaches have been designed for the micropropagation of elite date palm cultivars. The most commonly used techno­logy approach is somatic embryogenesis which presents a great potential for the rapid propagation and genetic resource preservation of this species. Considerable progress has been made in the development and optimization of this regeneration pathway through the establishment of embryogenic suspension cultures. However, several problems still need to be solved and are currently under study, such as the abnormal differentiation of somatic embryo, the proliferation of endophytic bacteria within in vitro cultured material and the occurrence of somaclonal variants in regenerated offspring. The present review is aimed at providing updated and innovative information on recent progress, applications and prospects for somatic embryogenesis in the date palm.

Date Palm Micropropagation via Somatic Embryogenesis

While describing major trends of carbon metabolism during the initiation and expression of somatic embryogenesis in date palm (Phoenix dactylifera L., cv. Deglet Nour), we have investigated the role of two carboxylases, namely PEPC (Phosphoenolpyruvate carboxylase, EC 4.1.1.31) and RubisCO (Ribulose 1,5-bisphosphate carboxylase/oxygenase, EC 4.1.1.39), in embryogenic and non-embryogenic cultures. The detection of PEPC activity on polyacrylamide native gels after electrophoresis revealed the presence of 3 active isoforms in crude extracts from the embryogenic (E) callus strain, whereas only a single band was present in the non-embryogenic (NE) one. The level of PEPC specific capacity was of the same order (3.9 ± 1.2 μmol CO2 h−1 mg−1 TSP) in both types of cultures. Further changes in carboxylase (PEPC and RubisCO) activities during the growth and development of somatic embryo–derived plantlets were also analysed. The PEPC/RubisCO ratio was found to progressively decrease (from 17.7 to 0.2) throughout the in vitro development of plantlets, due to a substantial depletion of PEPC activity, which decreased from 5.3 to 1.2 μmol CO2 h−1 mg−1 TSP. Concomitantly, RubisCO assumed greater importance (from 0.3 to 5.3 μmol CO2 h−1 mg−1
 TSP
 ) and became the main route for inorganic carbon fixation. Western blot analysis using polyclonal antibodies raised against PEPC and RubisCO purified from tobacco leaves confirmed this trend in terms of relative enzyme abundance.

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Carbon metabolism in in vitro cultures of date palm: the role of carboxylases (PEPC and RubisCO)

This chapter describes an efficient protocol for large-scale micropropagation of date palm. Somatic embryo-derived plants are regenerated from highly proliferating suspension cultures. Friable embryogenic callus is initiated from juvenile leaves using slightly modified Murashige and Skoog (MS) medium supplemented with 0.1 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D). Suspension cultures consisting of proembryonic masses are established from highly competent callus for somatic embryogenesis using half-strength MS medium enriched with 0.1 mg/L 2,4-D and 300 mg/L activated charcoal. The productivity of cultures increased 20-fold when embryogenic cell suspensions were used instead of standard protocols on solidified media. The overall production of somatic embryos mostly exceeds 10,000 units per liter per month. Partial desiccation of mature somatic embryos, corresponding to a decrease in water content from 90 down to 75%, significantly improved germination rates. (Resume d'auteur)

R. Masmoudi

Papers

An optimised protocol for plant regeneration from embryogenic suspension cultures of date palm, Phoenix dactylifera L., cv. Deglet Nour

Date Palm Micropropagation via Somatic Embryogenesis

Carbon metabolism in in vitro cultures of date palm: the role of carboxylases (PEPC and RubisCO)

Indirect Somatic Embryogenesis of Date Palm Using Juvenile Leaf Explants and Low 2,4-D Concentration.

Production de vitroplants de palmier dattier à l’échelle pilote