The Use of GM Crops in Developing Countries
Case study 6: Improved resistance to diseases in bananas
3.53 Bananas make important contributions to food security in many developing countries. Leaves and fibres are used for a multitude of household and industrial purposes. Bananas also provide income to the farming community through local and international trade. World production of bananas is estimated to be approximately 70 million tons per year, of which around 85% are grown for local consumption by tropical, small-scale farmers.76 Approximately half a billion people in Asia and Africa depend directly on farming of bananas. In Uganda, the crop is cultivated on one third of the arable land, and per capita consumption is 50 times higher than in the UK.77
3.54 Like all plants, bananas attract a range of different and highly adapted pests. However, in bananas these can have a particularly harmful effect. Unlike most plants, bananas only reproduce asexually, because the cultivated form is a sterile triploid. The different varieties grown around the world today have been cultivated from shoots of a small number of naturally occurring mutants. These have been derived from an even smaller number of manmade triploid varieties, some produced over a hundred years ago. Each ‘variety’ is therefore a clone, and the crop species is characterised by a very low level of genetic diversity. There is little hope that conventional plant breeding will produce crops that are resistant to bacterial or viral infections.78 However, GM technology offers possibilities of increasing resistance to pests and diseases. It may also help to increase the diversity of banana varieties, which in turn could contribute to slowing down the impact of pests.
3.55 Common infestations of bananas include nematodes, viruses, and fungal diseases. The most harmful fungal disease is black Sigatoka which can reduce fruit yields by as much as 50-70%. It can cut the productive lifetime of a plant from approximately 30 to two or three years. Usually, up to 40 sprayings of fungicide are applied annually to afford protection from the fungus. These sprayings represent up to a quarter of the production costs, are environmentally problematic, and a cause of considerable ill health of farm workers. According to a 1999 study by the National University of Costa Rica, one fifth of the male workers on banana farms in Costa Rica are sterile. It has also been reported that female workers have a 50% increased chance of developing leukaemia and of passing on birth defects to their children.79
3.56 One of the goals of a public, global biotechnology consortium led by the International Network for the Improvement of Banana and Plantain (INIBAP) is to sequence the genome of inedible wild bananas from South East Asia, as these are resistant to black Sigatoka.80 It is hoped that the project will help identify genes which confer resistance. Once identified, the gene(s) could be introduced in leading varieties of edible bananas.81 Other research is being undertaken to produce bananas that are resistant to nematodes,82 or to viral diseases such as the banana bunchy top virus or banana bract mosaic virus.83 There are also other forms of biotechnology-aided plant breeding, such as tissue culture, which have already resulted in improved, disease free crops.84
Footnotes76 FAO (2002) FAOSTAT. Available: http://apps.fao.org/. Accessed on: 20 May 2003.
77 Pearce F (2003) Going bananas, New Scientist 177 (2378): 26–9.
78 Conway G (2003) From the Green Revolution to the Biotechnology Revolution: Food for Poor People in the 21st Century. Speech at the Woodrow Wilson International Center for Scholars Director’s Forum. 12 March 2003. Available: http://www.rockfound.org/documents/566/Conway.pdf, p19. Accessed on: 10 Oct 2003.
79 Smith J (2002) The truth about the banana trade, The Ecologist 22 March 2002. We note that one of the most dangerous chemicals, dibromochloropropane has now been banned. Rates of other types of cancers have been shown to be increased amongst Costa Rican banana plantation workers as compared with the national incidence rate, see Wesseling C, Antich D, Hogstedt C, Rodriguez AC and Ahlbom A (1999) Geographical differences of cancer incidence in Costa Rica in relation to environmental and occupational pesticide exposure, Int J Epidemiol 28: 365–74
80 INIBAP is a programme of the International Plant Genetic Resources Institute (IPGRI).
81 Pearce F (2003) Going bananas, New Scientist 177 (2378): 26–9. AstraZeneca is also developing cultivars with resistance to black Sigatoka, see Biotechnology Industry Organization Agricultural Biotech Products on the Market. Available: http://www.bio.org/food&ag/approvedag98.html. Accessed on: 20 Oct 2003.
82 Researchers at the Catholic University of Leuven are developing banana cultivars with resistance to nematodes and to fungal diseases, which can lead to an average 20% loss in banana plantations. KU Leuven Laboratory of Tropical Crop Improvement. Available: http://www.agr.kuleuven.ac.be/dtp/tro/home.htm. Accessed on: 22 Oct 2003.
83 Research at the Catholic University of Leuven and at Queensland University of Technology in Australia has focused on developing bananas which are resistant to these viruses, which are among the major viral diseases relevant for bananas worldwide. KU Leuven Laboratory of Tropical Crop Improvement. Available: http://www.agr.kuleuven.ac.be/dtp/tro/home.htm. Accessed on: 22 Oct 2003; Demegen (2001) International Plant Biotech Groups Collaborate. Available: http://www.demegen.com/prs/pr011213.htm. Accessed on: 22 Oct 2003.
84 Wambugu FM and Kiome RM (2001) The Benefits of Biotechnology for Small-Scale Banana Producers in Kenya ISAAA Brief No. 22 (Ithaca, NY: ISAAA).