Bioscience in brief
Plant genetics and crop breeding
Is the current regulatory approval system unsuited for the improvement of vegetatively propagated crops by GM?
Cassava, bananas, sweet potato, potato, and sugar cane are among the most important crops grown in African countries. These crops provide a large proportion of the calorie intake for millions of people in developing countries.
These crops are reproduced vegetatively, by replanting cuttings or tubers. Reproduction by seed is not possible for banana, because this crop is sterile. Cassava, sweet potato, potato and sugar cane can be reproduced by seed.
However, improvement of these crops by conventional breeding methods is difficult. For cassava, the high level of heterozygosity, meaning the presence of different versions of one gene in the same plant, means the cultivars often do not breed true: the offspring do not resemble the mother plant because of genetic segregation during sexual reproduction. Long generation times, poor seed set and large space requirements for a breeding population add to the difficulty of the task.
Since the current unit of approval of GM crops is the transgenic event, plant breeders will have to either introduce by crossing an elite transformation event into the preferred varieties – for crops like cassava and banana there can be dozens in one country alone – or gain separate approval each time they generate a new transgenic variety.
The current system for vegetatively propagated crops will therefore be very expensive and time consuming. In addition, the system would actually decrease biodiversity, since plant breeders will concentrate on one or a few varieties, and if those deliver a large benefit to the farmers, there is a real risk of crowding out the diversity of varieties traditionally grown by in farming communities.
For these crops, a change of the unit of regulation will be essential for a realistic approval system.