以葉片揮發性成分組成鑑別酪梨單純品系間之親緣關係

Avocado (Persea americana Mill.) Genetic Relationship Identification Using Leaf Volatile Constituents as Indicators

本試驗樣品分別採自臺灣及薩爾瓦多，共22個品種，24個參試樣品。臺灣之樣品取自農業試驗所嘉義分所及沈清德先生果園，薩爾瓦多之樣品取自薩國農業試驗所種源保存區。比較樣品製備方法後，選用頂空－－固相微萃取聯用氣相層析質譜儀配合同位素標定之內標準品，分析酪梨葉片揮發性化合物組成且進行相對性定量。自單純品系樣品之氣相層析質譜儀分析結果，挑選12個品系專一化合物及10個數量級變異化合物，作為各酪梨品系之特徵指標化合物。數據分析以歐式距離計算特徵指標化合物相對校正量，取普通對數值之相似性矩陣，再以非加權配對算術平均法進行群聚分析。此數據分析結果繪製之群聚樹狀圖中，三大類酪梨單純品系樣品可明顯區分為三大群，與文獻之酪梨品系分類結果相符。以揮發性化合物組成作為親緣關係之鑑別方法，具試驗重複性與再現性、實驗操作簡單及分析快速等優點。分析資料可加入資料庫中，並與資料庫中之資料合併加入群聚分析。此分析模式未來應可用於其他物種之親緣關係檢測。 Twenty-four leaf samples in twenty-two avocado pure race cultivars were collected in Taiwan and El Salvador. Taiwan avocado leaf samples were collected from Chia-yi Agricultural Experimental Station (CAES) and Shen's orchard. Import leaf samples were supplied by Germplasm Reserves of Institute of Agricultural Experiments in El Salvador. In comparison with headspace-gas tight syringe direct injection, solvent extraction, pyrolysis, and headspace-solid phase microextraction, HS-SPME was chosen for sample preparation. HS-SPME GC-MS utilizing EPA Method 8270 stable isotope internal standards provide a sensitive and reproducible quantitative method for analyzing avocado leaf aroma. Twelve race-specific compounds and ten magnitude-varied compounds were selected as the characteristic indicator compounds for further analysis. Chavicol and methyl eugenol, sesquiterpene I and sesquiterpene III, were race-specific compounds for Mexican and Guatemalan race. Hexanal, phenylacetaldehyde and caryophyllene isomer were race-specific compounds for West Indian race. β-myrcene, γ-terpinene, and nonyl aldehyde could only be found in Guatemalan and West Indian races, trans-anethole could only befound in Mexican and West Indian race, sesquiterpene IV could only be found in Mexican and Guatemalan race. The magnitude-varied compounds included terpenoid, aldehyde and phenylpropanoid, such astrans2hexenal, α-pinene, β-pinene, limonene+eucalyptol, estragole, α-copaene, sesquiterpene II, caryophyllene, α-humulene, and sesquiterpene V. Similarity matrix of volatile constituents was calculatedby Euclidean distance of base10logarithm value of characteristic indicator compounds calibratedabundance, and dendrogram was clustered based on unweighted pair group method arithmetic average (UPGMA). Three avocado horticultural race samples were separated into three major groups on the dendrogram of volatile constituent test results. The cluster result of test samples agreed with the classification information from literature review of three races. The total ion chromatogram of 'Horshim' was identified as the hybrid between Mexican and Guatemalan races. Because of the benefits of easyoperation, fast analysis, good repeatability and reproducibility, volatile constituent analysis of avocado leaves could be used as a morphological chemotaxonomy method. Calibrated abundance by internal standards of testing data of GC-MS could be merged into database, and generated a new dendrogram with the all data in the database. Experimental results proved that this is a feasible method for genetic relationship identification.