Study On Transgenic Detection With PCR And Feeding Safety Of Glyphosate-tolerant Soybeans

This paper was conducted to study PCR methods for detecting exotic genes from genetically modified (GM) RR glyphosate-tolerant soybeans, soybean meal and feedstuffs, and to make a safety assessment for its application in animals.Qualitative and quantitative PCR methods for detecting GM soybeans and its derivative feedstuffs were developed. Firstly genomic DNA was obtained with CTAB method or kit for extraction from GMO. After qualitative PCR was used to screening and amplify different target genes in the exotic gene cassette, the PCR products were recovered and cut further with the corresponding restrictive enzyme. The limit of detection was 0.1% with qualitative PCR. When nested PCR was employed, as little as pg of soybean template DNA could be detected. Based on the detection with double-primer PCR, the soybeans and feedstuffs from America and Argentina were GM positive. In addition, real-time quantitative PCR method was developed with fluorescence dye SYBR Green I what combined to double-strand DNA. The standard curves of lec and CaMV35s genes were drawn with 0.9997 and 0.9992 of R2 value respectively. The relative deviation was within 5~11% between the determinated and actual values of known levels of standard or simulated soybeans.A series of experiments including growth of weanling piglets, digestion of grower pigs and subchronic toxity of rats were conducted to evaluate feeding value and safety of soybean meal from GM RR glyphosate-tolerant soybeans. The analyzed proximate nutrient, amino acids, trace mineral, fatty acid and anti-nutrition factors such as trypsin inhibitor in RR soybeans or soybean meal were within the normal range. RR soybean meal had no significant effects on performance and blood physiological and biochemical parameters of weanling piglets. The experiment of grower fitted with a T-cannula at the distal ileum showed that ileal apparent and true digestibility of crude protein and amino acids were not different between the conventional and RR soybean meal. There were no deposition of cp4 epsps gene in liver, muscle, spleen and thymus tissue, but this gene was found in chyme and feces both only at 6.7%. In subchronic feeding study on 80 Sprague-Dawley rats for 13 wks, both growth and feed intake of rats fed 60% conventional and GM RR soybean meal were not significantly different (P > 0.05). Hematology, serum and urinalysis parameters were not beyond normal physiological range in rats fed high level of 90% RR soybean meal. No death, macroscopic changes and histopathological lesions were observed. Neither exotic nor endogenic DNA was detected in masseter muscle, hi conclusion, GM RR glyphosate-tolerant soybeans is essentially equivalent in composition, nutritional availability to weanling piglets and grower to the conventional, and should be considered as safe for rats feeding.