臺灣野豬與臺灣商用豬種之親源關係研究

Abstract

臺灣原生豬種計有臺灣野豬、桃園豬、蘭嶼小耳豬等；臺灣野豬為臺灣山區分布最廣泛的中大型野生動物，在全臺各地的林地內幾乎皆可看到其活動痕跡。過去對於臺灣野豬之研究大多偏向於在山區出現之頻率或是對人類農作物破壞等。微衛星標記為目前公認最具資訊之族群遺傳研究工具，而粒線體為母系遺傳，其cytochromeb 區域適合做為探討族群間之差異程度。2007 年起自宜蘭、南投、花蓮、高雄、台東及屏東地區收集臺灣野豬樣本，以PCR 增幅微衛星標記以及粒線體cytochrome b 區域後進行分析。經比對粒線體D-loop 序列後，排除帶有非臺灣野豬（蘭嶼小耳豬或其他圈養之家豬之粒線體序列）之個體，以73 頭進行微衛星標記分析。cytochrome b 分析全長1140 bp 後共19 個單倍型（haplotype），由遺傳結構對照其地理分布，可見大多單倍型具有其地理獨特性。微衛星分析之RST 值在不同地區間為0.0056∼0.1643，除屏東地區外，其他不同地區間之分化程度不高（0.0056∼0.0812），基因交流為其可能原因，而屏東地區與南投、花蓮與宜蘭地區分化程度高於高雄、台東地區之原因可能為其地理距離影響基因交流所致。根據粒線體以及微衛星之屬性，可推測臺灣野豬母豬較具有地域性，而公豬則會遷徙導致發生基因交流情形。蘭嶼小耳豬在1980 年自蘭嶼引入畜產試驗所台東種畜繁殖場後，除保留原始族群外，亦選育具有花斑體表之花斑豬與白色體表之賓朗豬，以因應國內對生醫研究用實驗動物之需求。此外，國內各機構亦利用品種雜交互補性，育成兼具本土特色與外來種優勢之合成豬種，先後計有臺灣大學畜牧系 (動物科學技術學系前身) 之李宋豬 (3/4 蘭嶼小耳豬，1/4 藍瑞斯)、畜產試驗所之畜試黑豬一號 (1/4 桃園豬，3/4 杜洛克)、臺東種畜繁殖場之迷彩豬 (1/2 蘭嶼小耳豬，1/2 杜洛克) 與高雄種畜繁殖場之高畜黑豬(1/2 梅山豬，1/2 杜洛克)，而舉凡此等合成豬種之商業行銷、遺傳品質監控與繁殖管理勢需予以重視。以19 個微衛星標記分析上述各豬種間之Cavalli-Sforza chord distances 介於0.333∼0.799，遺傳分化指數 (FST value) 介於0.168∼0.502，後者顯示各豬種間皆具有中等程度以上之分化，即各純種與合成豬種皆有獨特之遺傳組成。全部樣本另經分派檢定（assignment test），以19 組微衛星標記分析結果顯示所有個體落在其本身所屬豬種內之正確率為99.4%，並以各標記遺傳分化指數（FST）、期望雜合度以及對偶基因數目進行排序，以蘭嶼小耳豬及其相關族群的數據集（dataset）計算上述三種數值並依高低挑選不同數目之標記進行分派測驗，可發現在依照較高期望雜合度下，使用9 個微衛星標記即可達到99.7% 之高正確率。故本研究所建立之微衛星資料足可辨識豬隻之品種，並能據以應用於豬群之遺傳管理。

The indigenous pigs in Taiwan included Formosan wild boar, Taoyuan pig and Lanyu pig. Formosan wild boars extensively distributes in wild of Taiwan. At past, the studies of Formosan wild boars were focused on their distributions, behavior and the conflict with human. The genetic study in Formosan wild boars was scarce. PCR-based DNA approaches including AFLP, sequences and microsatellites were widely used for studying population structure and biodiversity of pigs (Sus scrofa). In these molecular markers, mitochondrial cytochrome b sequence which was maternal inherited was suitable for differeitiation between populations. Microsatellite markers with highest polymorphism were commonly used in population structure studies of wildlife and livestock. One of the purposes of present study is to investigate genetic structure and their phylogeographic relationships based on the cytochrome b sequences and polymorphisms of microsatellite loci. Since 2007, Seventy-three blood or muscle tissue of Formosan wild boars were collected from mountain areas located in Yilan, Nantou, Hualian, Kaohsiung, Taitung and Pintung. All of 19 haplotypes of cytochrome b sequences were confirmed. Almost haplotypes were appeared in specific areas. Nineteen microsatellite markers which were recommended by International Society of Animal Genetics(ISAG) and Food and Agriculture Organization(FAO) were selected and used to examine in this study. RST values between different populations (range from 0.1643 to 0.0056) indicated existing population differentiations and the correlation between their genetic structures and geographical locations. Together these results, we suggest the sow Formosan wild boars were regional and the male Formosan wild boars migrated to occur the gene flow. Besides, long geographical distance form south to north Taiwan might cause their higher genetic differentiation. In domestric pigs, Lanyu and Taoyuan are indigenous breeds in Taiwan. The Spotty Lanyu and Binlang Lanyu were generated from inbreeding program of Lanyu breed. Many synthetic pig breeds were generated by crossing Taiwan indigenous pigs with exotic pigs to increase their applications and values. The synthetic pig breeds are including Lee-Sung (a hybrid of Lanyu and Landrance), TLRI Black Pig No.1 (a hybrid of Taoyuan and Duroc), Mitsai Lanyu (a hybrid of Lanyu and Duroc), and Kaohsiung Animal Propagation Station Black pig (KHAPS, a hybrid of Taoyuan and Meishan). To the aim of population management refered by genetic information, it is essential to monitor their genetic quality and breeding program based on molecular information. In addition, to establish the database including the genetic structure and the array of individual genetic distance among the indigenous, exotic and synthetic pig breeds in Taiwan is required for the purpose. Nineteen microsatellite markers were applied to construct the genetic database. Cavalli-Sforza chord distances in different breeds were between 0.333 to 0.799. The FST values (genetic differential index) were between 0.168 to 0.502, indicating medium differentiation among all breeds. The genetic database, genetic structure, the array of genetic variation and differentiation among these pig breeds were constructed based on 19 microsatellite markers. The microsatellite genetic information established from this study will be applied to diagnosis and identify the individual lineage of pigs and for population genetic management. To obtain high accuracy assignment of individual to their own origin, microsatellite markers were selected by the ranking of high heterozygosity, allelic number (K) or D-scores which were calculated based on power of discriminatory from all fourteen population database. In the assignment using the Bayesian methods, 99.4% accuracy assignment was obtained when using more than 9 markers with most high hetrozygosity, allelic number or high D-score. A very high performance assignment (99.7% correct assignment), 9 microsatellite markers with most heterozygous and rich allele numbers were selected based on the genotyping information only from Lanyu, its derived lines and derived synthetic breeds, was obtained to fit the purpose. The microsatellite genetic information provided by this study will be useful to obtain high performance assignment and identify an individual lineage to their origin, and apply for further genetic management and decrease the cost of DNA tracking of Lanyu, its derived lines and derived synthetic breeds.