The Applications of ISSR Markers and DNA Barcodes in Variety Identification of Tea
Date Issued
2009
Date
2009
Author(s)
Lin, Ya-Ping
Abstract
Tea is one of the most important economic crops in Taiwan. To ensure the authenticity of competition teas and to achieve traceability policy, an efficient method of variety identification for processed teas is urgently expected. In this study, twelve core markers and six auxiliary markers generated from seven ISSR primers and one functional gene were recommended to fingerprint prevailing tea varieties grown in Taiwan. The core markers are also suggested to examine the varieties of competition teas and commercial teas. According to ISSR DNA markers, some unknown varieties were found in the competition tea samples of Oolong tea and oriental Beauty tea. To enhance the efficiency of variety identification, two ISSR primers were randomly selected and mixed for PCR amplification. However, the unstable band patterns were found in many attempts. But stable markers could be obtained from electrophoresis with PCR products.TS2 (nuclear) and M8 (cytoplasmic) DNA sequences with large variations were screened out of twelve DNA fragments (four nuclear, four chloroplastic and four mitochondrial) to identify tea varieties in Taiwan. Among varieties of tea, thirty-three SNPs were found in the ITS2 fragments, and five InDels and two SNPs were found in the M8 fragments. DNA mixtures of different varieties with various ratios (50%, 40%, 30%, 20%, and 10%) were identified based on sequencing signals of SNPs or InDels of M8 fragments. In order to apply DNA barcodes in variety identification of made teas, the primers were designed to amplify short fragments within the length limitation of one confident sequencing. The ITS2 and M8 sequences were recommended as DNA barcodes for commercial teas. Mixture of different varieties that was unable detected by ISSR DNA markers was verified by ITS2 and M8 DNA barcodes.ur studies have demonstrated that ISSR DNA markers are useful in variety identification of teas. However, they lack in sensitivity to detect variety mixtures. On the other hand, DNA sequence barcodes could detect variety mixtures. In this study, DNA sequence barcodes are suggested to be applied in labeling, tracing or primarily detecting commercial tea products, and ISSR DNA markers are prepared for reconfirmation of variety identification.
Subjects
DNA barcode
ISSR marker
made tea
variety identification
variety mixture
Type
thesis
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