Millions of date palms are lost as a result of the Bayoud disease. Breeding Bayoud resistant varieties is complicated by the highly specific micropropagation protocol for each date palm variety, plus regional differences in varietal demand. An international date palm network could be a cost­effective way to collaborate in biotechnology research.

About 105 million date palms (Phoenix dactylifera L.) are grown in the Middle East, Africa, USA, Middle and South America, Spain and Italy. To grow well, "the palm must stand with its feet in the water and head in the hot sun". Thus an oasis in the desert is the most suitable environment for date palm.
The date palm is an important multi­purpose tree. In many African oases the date palm helps to prevent erosion and is necessary for the protection of cereals, other fruit trees and grasses from direct exposure to the sun. In addition, the date fruits have high nutritional value and are easy to store since they are relatively non­perishable. Products from the date fruits include syrups, jams and beverages. Building materials and handicrafts are produced from the trunks and leaves. Date seeds are used for animal feed. The palm requires limited inputs and can be productive for about 65 years. For many farmers, date is both a consumption and a cash crop. Published data regarding date palm production is difficult to find. As an indicator, in Morocco for example, date palms supported about two million farmers for about 80 per cent of their subsistence.
However, the Bayoud disease, caused by the soil borne fungus Fusarium oxysporum, is a lethal threat to the date palm. In Morocco and Algeria, the fungus has killed more than 13 million trees. While economic losses are difficult to calculate, social and environmental contributive effects are apparent. These include desertification, soil erosion, and urban migration. The Bayoud disease has not yet spread to Tunisia. When this happens, the devastation will be enormous since the country mainly uses the Deglet Noor variety, which is very sensitive to the Bayoud disease.
The replacement of Bayoud­infested palms is problematic. The available Bayoud­resistant varieties generally do not produce good quality fruits. At the same time, conventional breeding for resistance and quality is very time consuming. It usually takes at least 30 years to make three back­crosses, and to obtain the first offshoots from an inter­varietal cross. While trees produce plenty of seeds, the progeny of sexual propagation is often very different from the mother tree because of genetic variation within species. In addition, date palms are of single sex, and it takes 8 years for the female seedlings to bear fruit. The potential of asexual propagation through offshoots is limited. The offshoots are produced from axillary buds at the base of the trunk during the juvenile stage of the palm tree. However, a female tree gives only 10 to 30 transplantable offshoots, and propagation is time consuming.

Developments in reproduction
Until now, micropropagation of date palms by tissue culture has had very limited success. Many of the problems are due to the agronomic characteristics of the date palms, but failures are also caused by lack of research collaboration. Of the 25 groups active in date palm research worldwide, five are private companies. Four of these companies, located in the USA, Israel, UK and France, propagate plantlets through somatic embryogenesis. This technique involves generating embryos from cells not stemming from the reproductive organs of the plants. This technique was established for date palm by plant breeder Tisserat in 1979. With somatic embryogenesis it is relatively easy to produce plantlets on a large scale. However, the required high level of hormones in the media make the plantlets susceptible to mutations. To make things worse, deviations are detectable only after 6 to 8 years of planting in the field. Farmers often pay for these losses.
The fifth private company, El Bassatine in Morocco, has probably been the most successful in date palm micropropagation. They use organogenesis, i.e. plant regeneration from single cell via organ­like structures, often shoots. This technique was established for date palm in 1979 by plant breeders Beauchesne and Rhiss. Plantlets produced through organogenesis are not prone to mutations since low levels of hormones are used in the medium. However, the technique has not been very successful in producing plantlets on an industrial scale. Most plantlets do not survive the rooting stages at the laboratory.
In the meantime, the Institute National de la Recherche Agronomique (INRA) of the Moroccan government, in close collaboration with El Bassatine, has found protocols to scale up a few varieties with organogenesis. INRA has also bred Bayoud resistant varieties that produce good quality fruit. However, for these varieties specific protocols have not been developed yet.

Too many varieties, too many protocols
Most of the more than 3000 date palm varieties grown worldwide require specific protocols for large­scale micropropagation. For example, some varieties need more sugar in the medium, while others require more vitamins, nitrogen or calcium. Basic research to tackle these differences systematically is scarce.
One of the institutes specialized in molecular methods for date palm is Wye College, UK. It uses DNA fingerprinting to determine genetic differences between varieties with different protocols. Another institute specializing in these variety problems is Phoenix, a publicly funded research station in Spain. It examines various media to correlate to protocols for date palm varieties.
To reduce research in protocols narrowing varietal choices for worldwide sale is not a viable option. First, many significant varieties can only grow in their own region. Second, and more important, inhabitants of a region prefer the taste and quality of their traditional varieties. Obviously, they will only use another variety if it has improved yield or taste. This is not often the case, due to the lack of breeding activities worldwide. Third, several countries forbid the import of foreign varieties since they fear Bayoud­infected materials.

Networking
The exchange of knowledge and experience is increasingly stimulated through collaboration and various consultations. For example, the London based consultative group, Nakhlatec, was set up by the Wye College in 1995. Nakhlatec offers planning and management services in research and production to date palm producers and laboratories worldwide. Part of the agenda will be the comparative analysis of different varieties' recalcitrance to tissue culture. They hope to encourage openness and confidence in handling research failures.
Another example of collaboration was the first international meeting of date growers, companies, government officials and nearly all of the 150 researchers worldwide in 1995. Organized by Phoenix, the subjects varied from crop management, tissue culture to socio­economic aspects such as farmers' participation in disease control. One­third of the congress members have already agreed to establish an international association on date palm in the near future.
According to both Nakhlatec and Phoenix, a date palm network needs to coordinate research priorities and specializations. At this point, severe disagreements can be expected, especially about the need for genetic engineering. Many research institutes, also in the South, are looking for methods to develop transgenic date palms since they find classical breeding too time consuming. Michel Ferry from the Phoenix station stresses that genetic engineering is not a priority that could benefit farmers, as long as tissue culture propagation of elite varieties remains highly problematic. This is because tissue culture is a fundamental requirement to genetic engineering. He thinks genetic engineering is only important to scientists, as it is an exciting, new field with maximum possibilities for publication. However, Yaarub Al­Yahya of Wye College disagrees. He believes it is time to start research on genetic engineering after INRA's and El Bassatine's first successes in large scale micropropagation. According to Al­Yahya and Mustapha Ait Chitt of INRA, farmers could benefit when Bayoud resistant genes are transferred to elite date palm varieties.
Nevertheless, both Ferry and Al­Yahya agree that there must be a balance in both conventional breeding and biotechnology, as well as crop management and socio­economic research.

Profit considerations
Another reason for low research efforts in date palm is that profits could be low. L.H. Jones, a British plant breeder described the requirements for tissue culture of oil palms. He estimated that to be cost­effective, a propagation unit has to produce more than a million plantlets each year. If you compare the situation of oil palm to date palm, with 110 million date palms that can be productive for about 65 years, the world market needs only 1 to 2 million plantlets per year. Regardless of the significance of date palms in dry regions, demand will not increase due to water scarcity and urban migration from dry regions. In this scenario, there seems to be only one place for a viable date palm company to capture economies of scale on a global level. However, a single date palm company is, of course, not realistic. For one thing, it cannot respond to regional differences in demands. Thus, for more efficient and cost­effective propagation of improved date palms, collaboration is important amongst governmental institutes, private companies and (inter)national finance organizations.
Marianne Heselmans

Dijkgraafseweg 4, 6707 EL Wageningen, the Netherlands. E­mail heselman.gld.bart.nl

Sources
FAO (1984), Micropropagation of Selected Palms. Proceedings of symposium on plant tissue culture. FAO: Rome.

Nakhlatec (1996), Biotechnology and Date Palm Development. Homepages from the date palm consultative group, Wye College, University of London.(http://www.wye.ac.uk/agriculture/Uaps/ Datepalm.html).

Moroccan Date Palm Programme and Plant Biotechnology (1996). Proceedings of symposium integrating biotechnology in agriculture (Unpublished).

Personal communications with Yaarub Al­Yahya, (Nakhlatec), Mustapha Ait Chitt (INRA) and Michel Ferry (Phoenix Station).