A Study On Screening Germplasm Resources Of Oolong Tea Plant With Pesticide-resistance And Degradation Dynamics Of 4 Pesticides

Pesticide residues in tea influence on consumer health and impact earning foreign exchange. Utilizing oolong tea plant (Camellia sinensis (L.)O.Kuntze) in the Oolong Tea Variety Garden of Fujian WuYiShan and AnXi Tea Research Institute as materials, 4 pesticides (bifenthrin, fenpropathrin, cypermethrin and buprofezin) which presently exceed MRL in some oolong tea, were sprayed on experiment tea trees, the tea new shoots were plucked and processed, and their pesticide residue contents were determined and analyzed by gas chromatography. The cultivars or lines with pesticide-resistance had been screened, and the relative resistance mechanism was studied by the appearance and anatomical structure on tea leaves. At the same time, the natural degradation dynamics of 4 pesticides on tea new shoots as well as the degradation rate of 4 pesticides during oolong tea processing were studied. The main results were as follows:1. The oolong tea plant cultivars or lines with pesticide-resistance had been screened (bifenthrin, fenpropathrin, cypermethrin and buprofezin of 5, 4, 3 and 7,respectively).2. The half-lives of 4 pesticides in Tieguanyin tea new shoots were 6d, 5d, 4d and 4d, respectively. In Wuyirougui tea new shoots, 7d, 4d, 3d and 5d, respectively.3. In oolong tea processing the degradation rate of bifenthrin was 10.72%～53.47%, averaged 25.59%. Fenpropathrin, 9.09%～99.45%, averaged 36.07%. Cypermethrin, 21.59%～92.23%, averaged 43.53%. Buprofezin, 16.67%～100%, averaged 41.84%. Results show: the degradation rates in oolong tea processing revealed quite differently in both 5 cultivars suitable to Oolong tea and 4 pesticides.4. The resistance of tea plant varieties to pesticide correlates with leaf tine, saw tooth, ratio of cutin layer/palisade tissue, ratio of cutin layer/spongy tissue, ratio of upper epidermis/cutin layer and ratio of lower epidermis/cutin layer. The tea plant varieties with pesticide-resistance had characters as follows: sharp leaf tine, more saw tooth, low ratio of cutin layer to palisade tissue, low ratio of cutin layer to spongy tissue, high ratio of upper epidermis to cutin layer and high ratio of lower epidermis to cutin layer. And the tea plant varieties with high pesticide residue content reversed.