The false dilemma raised by genetic engineering experts
Until now, protests against genetic engineering for the purpose of protecting plants against disease have focused on the unpredictable and uncontrolled repercussions on the ecosystem from the introduction and spread of «foreign» genes. These protests are not unfounded. First of all, it is impossible to control the spread of these genes from one species to another. We have already seen the first adverse effects, as the gene for rapeseed’s resistance to the herbicide glyfosate has already been found in various species of wild mustard. Unusual behavior in bees seeking food among GM plants has been reported. Many batches of GM seeds have been withdrawn by the manufacturers because they have caused food allergies. Producers using GM reproductive material are now absolutely dependent on the manufacturers, who are able modify it in such a way that it cannot be reused. Mark Henderson’s recent article in New Science is an indication of an attempt by genetic engineers to create pseudo-dilemmas as a means of going on the counterattack. So they claim banana cultivation will disappear if the species is not genetically modified in order to resist damage from fungal diseases such as Sigatoka or Fusarium wilt (Panama disease, caused by Fusarium oxysporum f.sp. cubense) These references are accompanied by predictions of doom; that in 13 years’ time the two main cultivated varieties, Gros Michel and Cavendish, will disappear. These are portentous words indeed, and ones that will open the way to genetic engineering in the cultivation of the banana crop. It is true that banana crops have been affected in recent years by many diseases and animal pests. Fungal infections which under certain conditions, particularly the intensive form of conventional cultivation, cause major damage. These are: – Yellow Sigatoka leaf spot, caused by the fungus Mycosphaerella musicola, first observed in 1902; – Black Sigatoka leaf spot, more aggressive than the yellow variety and which first appeared in 1963 in the Fiji islands, hence its name, Mycosphaerella fijiensis. Also important is the soil disease Fusarium, as well as Moko disease caused by the bacterium Ralstonia solanacearum. The rapid rate of damage observed in recent years, particularly from Sigatoka, is due to the uncontrolled use of mainly protectant fungicides to which pathogens easily built up a resistance. The failure to alternate between protectant and systemic fungicides has led to the prevalence of resistant strains of these pathogens, against which modern fungicides are ineffective. Therefore the use of systemic fungicides, in combination with paraffin spray oils and the restricted use of protectant fungicides, would reduce incidence of disease to a considerable extent. Efforts have also been made to produce disease-resistant hybrids. There is a large source of genetic material available, since there are many species of bananas which in practice are resistant to cercosporiasis. In Cameroon, considerable efforts have been made in this direction. Moderate biotechnology has promoted the use of many allelochemicals which restrict attacks either by direct fungicidal action or by stimulating the plant’s immune system. Regarding Fusarium, efforts are being made to use soils that are naturally resistant to pathogens of the mycorrhizal fungus Glomus intraradices as well as organic disinfectants. And in the treatment of Moko disease, making use of naturally resistant soils should be studied. The false dilemma about the destruction of banana crops that are not genetically modified does not convince anyone. There is a great biodiversity within genetic material which can be produced by means of cross-species fertilization and hybridization of varieties with genes that are resistant to disease and with the desired standard of quality. The holistic study of all the factors in the specific patho-ecosystem and in moderate biotechnology can result in satisfactory solutions. This chemical method, when implemented fully, is able to restrict damage from disease. Therefore any prophecies of doom are misleading and suspect. It should be emphasized that the above-mentioned diseases should not concern Greek banana farmers, since these pathogens have not been observed here. Vangelis Bourbos is an agronomist and phytopathology researcher, eco-toxicologist and director of the Institute for the Olive and Subtropical Plants.
