Scientists have genetically modified Mediterranean fruit flies so that their offspring die young, a move they hope will control the spread of the devastating crop pest.

Ceratitis capitata — known as medfly — devastates a range of fruit crops and is found in many tropical and subtropical regions.

One current control method sees male flies made sterile by irradiation and released into medfly populations, where they compete with normal males to mate with females and decrease the number of offspring in a population.

But irradiation damages the flies, making them less able to outcompete their normal counterparts.

German researchers have introduced a set of genes into male fruit flies that kills their offspring as embryos, wiping out that generation. Larvae never develop, so there is no damage to the fruit crops in which they usually grow, and concerns about the genes being released into the wild population are unfounded because there are no offspring to pass the genes on.

This technique is better than irradiation because it doesn't damage the fly's ability to compete with normal males, meaning fewer flies might be sufficient for pest control, Ernst Wimmer, professor of developmental biology at the Johann-Friedrich-Blumenbach-Institute of Zoology and Anthropology in Germany, told SciDev.Net.

But there is further work to do because this technique can be rolled out, including ensuring that only male genetically modified (GM) flies are produced during mass rearing and adding fluorescent markers to improve monitoring of the GM flies in the field, says co-author Marc Schetelig, a molecular biologist at US-based USDA/ARS Center for Medical, Agricultural and Veterinary Entomology.

Mohammed Hamoud, head of the genetic research division at Egypt's Tanta University's botany department cautiously welcomed the research findings, acknowledging the potential usefulness of GM insects for plant protection to reduce over-reliance on pesticides.

But he pointed out, "The produced GM insect has only been tested in laboratory and contained field cages, and there is no way to predict the fate of a modified gene's effect on the environment after open field release."

He called for a thorough regulatory framework to identify, assess and manage any risks associated with the use of GM insects for crop protection.

Source: SciDev net
Date: 3 February 2009