Biodegradation of genetically modified seeds and plant tissues during composting.
BACKGROUND
The increasing global market of genetically modified (GM) crops amplifies the potential for unintentional contamination of food and feed with GM plants. Methods proposed for disposal of crop residues should be assessed to prevent unintended distribution of GM materials. Composting of organic material is inexpensive and location-independent. The objective of this study was to determine the effectiveness of composting for disposal of GM plants in terms of reducing seed viability and promoting the degradation of endogenous as well as transgenic DNA.


RESULTS
Duplicate samples of corn kernels, alfalfa leaves, and GM canola seeds, meal and pellets were sealed in porous nylon bags and implanted in duplicate 85,000 kg (initial weight) feedlot manure compost piles. Samples were collected at intervals over 230 days of composing. Canola seeds and corn kernels were not viable after 14 days of composting with temperatures in the piles exceeding 50 degrees C. In all samples, PCR analyses revealed that plant endogenous and transgenic fragments were substantially degraded after 230 days of composting. Southern blotting of genomic DNA isolated from canola seeds identified differences in the persistence of endogenous, transgenic, and bacterial DNA.


CONCLUSIONS
Composting GM and non-GM plant materials with manure rendered seeds non-viable, and resulted in substantial, although not complete, degradation of endogenous and transgenic plant DNA. This study demonstrates that composting could be effective for disposing of GM crops in the event of their inadvertent entry into the food or feed chain.
Reuter
Tim
T
Agriculture and Agri-Food Canada, Lethbridge Research Centre, P.O. Box 3000, Lethbridge, Alberta, T1J 4B1, Canada.
Alexander
Trevor W
TW
Xu
Weiping
W
Stanford
Kim
K
McAllister
Tim A
TA
D001673:Biodegradation, Environmental; D015139:Blotting, Southern; D018556:Crops, Agricultural / Q000235:genetics*; D004269:DNA, Bacterial; D018744:DNA, Plant; D008372:Manure; D018514:Plant Structures / Q000235:genetics; D030821:Plants, Genetically Modified; D012037:Refuse Disposal / Q000379:methods*; D012639:Seeds / Q000235:genetics*; D013696:Temperature; D014022:Tissue Survival
D004269:DNA, Bacterial; D018744:DNA, Plant; D008372:Manure