Investigation of False-positive Reactions for CBH351 Maize in Screening PCR Analysis

摘要

Examination for CBH351 maize was conducted by the qualitative polymerase chain reaction (PCR) method in maize grain and maize processed foods obtained in the Tokyo area. The numbers of samples possibly positive in the screening test were 7 of 22 (31.8%) for maize grain samples, 4 of 14 (28.6%) for semi-processed foods, 11 of 30 (36.7%) for canned products, 3 of 30 (10.0%) for maize snacks, 3 of 4 (75%) for tacos and 1 of 3 (33.3%) for tortillas. However, CBH351 maize was not detected in the confirmation test. Therefore, the results of the screening test were false-positive. Since the reaction might have been caused by the base sequences of the 3'-end of primers CaM03-5' and CBH02-3' used in the screening test, a new primer pair was designed. The PCRproducts obtained with the new primer pair TMC2-5'—TMS2-3' were specific for CBH351 and were not obtained with barley, wheat, rice, RRS, Btll, or Event 176. Thus, the new primer pair shows high specificity. CBH351 maize was detected from samples containing at least 0.05% CBH 351 maize DNA by using this primer pair.%東京都内で入手したトウモロコシ穀粒およびトウモロコシ加工食品について定性PCR法でCBH351トウモロコシの検査を実施した．スクリーング試験では103検体中29検体（28.2％）が陽性を疑わせる結果であった．しかし確認試験ではCBH351トウモロコシは検知されず，スクリーニング試験の結果は偽陽性反応であることが明らかになった．この原因としてはスクリーニング試験用プライマーCaM03－5'とCBH02－3'の塩基配列に起因する可能性が示唆された．スクリーニング試験における偽陽性反応を避けるため新たにプライマーの設計を行った結果，特異性が高く感度の良いプライマー対TMC2－5'－TMS2－3'が得られた．