Among the agrobiotechnology tools, in vitro micropropagation of plant tissues or organs, followed by clonal multiplication of the in vitro plants, ranks first in the propagation of a wide range of herbaceous and tree crop species.In the case of the banana tree, the example of Kenya is very illustrative of the benefits provided by agrobiotechnology. Unlike large parts of Latin America and other banana exporting countries, small farmers, mostly women, are the main producers in Kenya. They grow bananas for home consumption and the national market. It is the most popular fruit in Kenya, and cooking varieties are also an important staple food. Yet, the average banana yield in Kenya—14 tons per ha—is less than one-third of the crop potential under favourable conditions of the humid tropics. The main problem is the infestation of banana stock with weevils, nematodes and fungi, which cause severe diseases, such as Panama disease and black sigatoka. The resulting yield losses make banana a relatively expensive item for consumers. Producers also suffer reduced cash earnings, and the crop potential to contribute to the food security of rural households is undercut. A biotechnology project for the benefit of small-scale banana producers was facilitated by the International Service for Acquisition of Agri-Biotech Applications (ISAAA) and hosted by the Kenya Agricultural Research Institute (KARI) with funding from the Rockefeller Foundation and the International Development Research Centre, Ottawa (Wambugu, 2001). This model project included tissue culture technology for banana propagation and was awarded the 2000 Medal Prize Award by the Global Development Network—an initiative of the World Bank and the Japanese Government. The project benefited from a private–public partnership that demonstrated the feasibility of North–South technology transfer and the ability of resource-poor farmers to have access to research and technology innovations ensuing from appropriate linkages among partners. The project also benefited from a micro-credit programme that allowed small-scale farmers to buy superior pest- and pathogen-free planting materials.
The potential impact of bananas derived from tissue culture was analysed on three types of farms: small, medium and large (although even large-scale farmers have a mean banana area of only about 2 ha). Large farms increased average yields by 93% and medium-scale farmers gained 132%. For small holders, however, the increase was 150%. One farmer (Esther Gachugu) made up to $300 in one-day sale—more than she could earn in a year from a traditional banana orchard (Wambugu and Kiome, 2001). Other farmers built new houses, installed water tanks or sent their children to school. This success story shows the benefits African farmers can draw from horticultural crop biotechnology.
In addition to the direct impacts of the project, biotechnology distribution channels were established in order to facilitate the development of future innovations. For instance, as the international availability of transgenic banana varieties with resistance to major biotic stresses is expected by 2009, the project opens up avenues for the quick introduction of these and other promising biotechnologies for resource-poor farmers (Qaim, 1999).
In Uganda, substantial investments in research on banana and plantain have been made in recent years. This has culminated in the development of a biotechnology project in which the Government of Uganda provides the largest funding. The US Agency for International Development (USAID), the Rockefeller Foundation and Directorate General for International Cooperation (DGIC, Belgium) also allocate resources. The hub of the project is the National Agricultural Research Organization (NARO) together with Makerere University. Important partners include the Katholieke Universiteit Leuven (KULeuven), International Institute of Tropical Agriculture (IITA, Ibadan), French Agricultural Research Institute for Overseas Development (CIRAD), University of Pretoria and International Plant Genetic Resources Institute (IPGRI), which through its International Network for the Improvement of Bananas and Plantains (INIBAP) coordinates the project (Ortiz et al., 2002). The project aims at creating a biotechnological centre in Uganda and using genetic transformation for enhancing the resistance of the local East African highland bananas to the wide range of pests and diseases currently affecting the crop. The IITA provides technical backstopping for gene mapping of banana weevil resistance through an associated project, funded by a grant given to IPGRI/INIBAP by the Rockefeller Foundation.
In Morocco, with a production capacity of more than 1 million banana in vitro plants per annum, the company Domaines Agricoles, based near the city of Meknès, can meet the national needs for banana plants. These in vitro plants are raised in the nurseries located near Rabat and in the Massa area (Agadir region), which are the main banana-producing regions (Sasson, 2000).
Shoot-tip micrografting, together with thermotherapy, is the technology selected to clean citrus varieties from their viral, mycoplasmic and bacterial pathogens. Cleansed plant material can be obtained in 3 to 6 months instead of 10 to 15 years using conventional technologies such as nucellar selection or mass selection through indexing. Thus, since 1994, Morocco's Domaines Agricoles Unit of Plant Control has been able to clean about 20 commercially important citrus varieties, and produce certified and well-performing plant material (Sasson, 2000).
In air-conditioned greenhouses, one can experimentally control almost all viral diseases which affect citrus plants, i.e. about 30. These facilities enable the company to play an important role at both national and regional level for controlling the tristeza viral disease, a major threat to citrus cultivation. They also serve as quarantine facilities for introduced citrus species or varieties, in full cooperation with the Ministry of Agriculture Services of Plant Protection. The company took the initiative of undertaking a programme for the biological control of a citrus borer, Phylacnistis citrella, which originated from South-East Asia and invaded all citrus-growing Mediterranean countries in less than 3 years, causing heavy losses. Two natural enemies of the insect pest were introduced from Florida and Australia, Ageniaspis citricola and Semielacker petiolatus; hundreds of thousands of Ageniaspis citricola were produced and disseminated throughout the citrus-growing regions of Morocco. Algeria, Egypt and Spain also benefited from the Moroccan experience concerning the breeding of the useful insects. Another example of biological control is that against Aonidiella auranti, one of the oldest and major pests of citrus plants; chemical control is expensive, rather inefficient and can harm the exports of fruits because of the pesticide residues remaining on the fruit surface. A pilot unit was set up at the Domaines Agricoles to produce Aphitis milinus insects and to disseminate them in order to control the Californian lice (Aonidiella auranti) (Sasson, 2000).
The date palm is part of the landscape and a key element of land-use planning in large areas of African countries. It is also found beyond the eastern boundaries of the North African region, in the Near and Middle East, and has been introduced in several sub-Saharan countries, such as Namibia. It is the typical multipurpose tree crop of the oases from Morocco to Egypt, not only to supply dates (for local consumption and export), leaves and trunks as building materials, but more so to provide shade for barley and alfalfa cultivation under irrigation, and animal husbandry (sheep, goats and camels). Except for the case of plantations managed for exporting dates, e.g. in Algeria, Tunisia and Egypt, most date palm groves belong to families of resource-poor farmers and are the pivot of horticulture-type farming. Maintaining this tree crop is, therefore, a crucial socioeconomic issue for the development of marginal areas where date palm is growing; it is a way of controlling rural exodus and of mitigating rural poverty.
Although the date palm varieties grown throughout North Africa are quite sturdy, a fungal disease caused by soil-inhabiting Fusarium oxysporum subsp. albedinis, locally named as bayoud (meaning whitening, because white streaks appear on the leaves of the diseased tree), is causing havoc among the palm groves, particularly in Morocco. In this country, tens of millions of trees have been killed since the beginning of the 20th century. There is no effective chemical remedy for eradicating the fungus whose filaments penetrate through the roots and multiply in the vascular bundles, finally choking the tree (tracheomycosis). In addition to Morocco, which is severely affected, Algeria is also affected by this disease, although slightly less. The fungus may spread to Tunisia and even farther (in the Middle East, especially in the Gulf area, where the main pest of the date palm is the red weevil and the bayoud disease is unknown).
The threat is, therefore, very serious, and the whole ecosystem and way of life is being threatened, at least in the Moroccan oases. Fortunately, the Moroccan scientists of the National Institute for Agricultural Research (INRA) have been identifying, selecting and gathering many bayoud-tolerant date palm varieties, the clonal multiplication of which could be a viable solution. These scientists, with bilateral and multilateral assistance, have succeeded, many years ago, in micropropagating the date palm, starting from the caulinary meristems of offshoots (the tree produces a few offshoots over its life-span), and leading to uniform in vitro plants (through organogenesis). A private corporation, working in collaboration with INRA, is producing around 250 000 date palm in vitro plants per annum. This figure is far from meeting national needs, which are estimated as several millions per year if the medium-term objective is to replace the dead trees by tolerant varieties, and rehabilitate the oases and their specific agriculture (a National Plan for the Rehabilitation of Palm Groves was initiated in 1978).
The only agrobiotechnological tool available for such a purpose is that of somatic embryogenesis, which has been successfully used for several crop species, including the oil-palm, coconut and other tree species. Starting from leaf or inflorescence explants, using liquid instead of semi-solid medium, the production figures are of an additional order of magnitude compared to the organogenesis process. A difficulty relates to the inadvertent production of somaclonal variants, which may have abnormal inflorescences. Recent research overcomes this problem, and in fact several research teams in Europe have been able to produce large populations of normal date palm plants in vitro. Time has, therefore, come for the Moroccan relevant institutions to make the appropriate decisions in order to meet the huge needs of oasis farmers and to contribute to solving a very important socioeconomic problem.
Morocco has cooperated with Mali to introduce tissue culture-derived bayoud-free date palms into the north-eastern region of this country (Menaka), within the framework of an FAO project. Similar cooperation has been established with Libia (Sasson, 2000).
In Egypt, at El-Menoufia University, Sadat City, research is being carried out on the production of plants in vitro. A number of scientists belonging to this university have been trained in Germany and in the USA. The Genetic Engineering and Biotechnology Research Institute of this University succeeded in cloning date palm (Phoenix dactylifera cv. Zaghloul) through somatic embryogenesis and organogenesis. Successful regeneration of plantlets from the shoot-tip and leaf primordia derived from adult plants were reported. The Egyptian researchers are of the opinion that this method holds good chances for achieving mass production of true-to-type plants from adult date palm since the callus stage is avoided (Sasson, 2000).
Moving to somatic embryogenesis for multiplying bayoud-tolerant varieties does not preclude the pursuance of basic research on the molecular basis of the host–parasite relationship as well as on the genome of these varieties in order to identify a resistance gene(s) and stimulate plant-defence mechanisms. Any breakthrough achieved in date palm propagation, physiology and genetics will have a great impact on the socioeconomic development of the whole North Africa region and beyond.
In the Republic of South Africa, the Vegetable and Ornamental Plant Institute of the Agricultural Research Council (ARC-Roodeplaat) has developed tissue-culture protocols during the last 25 years for many vegetable crops—including root and tuber crops such as cassava and the research-neglected Livingstone potato (Plectranthus esculentus). Meristem culture and thermotherapy are used routinely for eliminating viruses in potato, sweet potato, cassava, garlic and indigenous ornamentals. The ARC-Roodeplaat provides all the virus-free material of sweet potato in South Africa. Its in vitro gene bank contains cultivars and breeding materials of potato, sweet potato, cassava and the ornamental Lachenalia spp. The Institute also carries out genetic transformation and molecular marker-aided selection (Ortiz, 2002b).
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