doi:10.1038/nindia.2015.1 Published online 12 January 2015
Based on pollination studies and DNA analyses, researchers warn there is high potential of transgenes from genetically modified (GM) brinjal contaminating its wild relatives growing nearby with implications for in situ conservation strategies of wild germplasm1.
The findings by the Indo-US collaborative study may be another hurdle to field trials of Bt brinjal in India, stalled by a moratorium imposed in 2010. "Our results suggest that transgenes would be introduced into populations of wild relatives of brinjal in southern India," the report says.
As part of risk assessment, regulatory agencies worldwide require information about the extent to which a GM crop will hybridise with its wild or weedy relatives and whether the transgenes are likely to spread from crop to crop. Many crops, including rice, are known to exchange genes with wild relatives.
"Till now this information was not available for brinjal (Solanum melongena)," Priya Davidar at the Department of Ecology and Environmental Sciences of Pondicherry University and lead author of the paper told Nature India. "To our knowledge this is the first study to show that hybridisation can occur between wild and cultivated brinjal due to cross pollination by native bees," the researchers report.
To determine the likelihood of gene flow from cultivated brinjal to wild relatives, the researchers focused on Solanum insanum, a wild/weedy variety that is very closely related to cultivated brinjal and is commonly found in roadsides, wastelands, near villages and agricultural fields.
During 2010–2014, they surveyed 23 populations of wild brinjal in Karnataka, Tamil Nadu and on the western flank of the Western Ghats in Kerala in southern India. Fourteen of the 23 wild populations occurred within 0.5 km of cultivated brinjal. At least 9 of the 14 wild populations had flowering times that overlapped with cultivated brinjal, providing opportunities for hybridisation. Most of the cultivated brinjal fields were irrigated, facilitating year-round cultivation and flowering. "Therefore, given the extended flowering of wild brinjal, the proximity of crop and wild populations, and the overlap in flowering times, we conclude that there is ample potential for gene flow between the two," the researchers report.
"We predict that if transgenic brinjal is widely grown in southern India, transgenes are likely to find their way into some wild, weedy, or feral populations," Davidar said. "This study fills a major gap in the scientific literature by demonstrating the potential for crop genes from transgenic brinjal to disperse into neighbouring populations of S. insanum if Bt brinjal is adopted in the future."
"The ecological and evolutionary consequences of such transgene escape, if any, will be influenced by the scale over which geneflow occurs and whether the transgenes are associated with any harmful or unwanted effects on valued non-target organisms," the report says.
The researchers note that social and political issues surrounding the introduction of Bt brinjal in India are complex, given the continuing debate over whether it is safe to eat. "Similar bio-safety questions are likely to arise in other parts of Southeast Asia where efforts are under way to introduce Bt eggplant, and our results about the potential for pollen-mediated gene flow to wild relatives may be relevant in these regions," the study concludes.