番茄抗晚疫病數量性狀基因座的遺傳定位

Abstract

番茄 (Solanum lycopersicum) 為臺灣及全世界重要的經濟作物，而晚疫病 (Late blight; Phytophthora infestans) 則為番茄重要的病害之一。臺灣早年田間晚疫病發病情況並不嚴重，但在1997年底到1998年初爆發嚴重的晚疫病疫情。自1997-1998年之後，晚疫病開始固定在冬春兩季發生。後續研究顯示，導致此疫情的主因是晚疫病新菌系US-11的出現，取代了原本的US-1菌系。新菌系對以往普遍施用的化學藥劑具有抗藥性，並可以耐受較高的溫度，這些都是造成晚疫病流行的原因。在晚疫病的防治方法中，種植抗病品種是一個有效且避免化學藥劑濫用的方法。本研究的目的為利用數量性狀基因座定位法 (Quantitative trait locus; QTL)尋找抗病野生種番茄L3708 (Solanum pimpinellifolium)所具有的抗晚疫病基因，並且透過台灣抗晚疫病的野生種番茄L3708 和感病的栽培種番茄T3224為親本，雜交產生F2:3遺傳定位族群進行試驗。試驗結果共定位出兩個數量性狀基因座，分別位於第二號染色體上的分子標記SLP_0201至SLP_0207之間以及第九號染色體上的分子標記TG591和CT220a之間。而定位到第九條染色體分子標記TG591和CT220a之間的數量性狀基因座和前人發表的番茄抗晚疫病基因Ph-3定位到相同的區間；進而，本研究針對位於第九號染色體上的抗病基因Ph-3進行高解析度遺傳定位，將Ph-3基因的定位區間縮小到22kb。經基因註解和比對，此區間共比對到4個候選基因 。

Tomato (Solanum lycopersicum L.) is a popular and important vegetable crop in the world. Late blight (LB) caused by the oomycete Phytophthora infestans (Mont.) de Bary is one of the major tomato disease with global importance. Before 1997, late blight only occurred sporadic in the high and cold areas in Taiwan. At the end of 1997, a severe epidemic outbreak on occurred in the potato fields in Taichung. And since then the disease often occurs in winter and spring. Studied showed the epidemic was associated with the population changes in Phytophthora infestans in Taiwan. The isolates found before 1997 belonged to US-1 clonal lineage. After 1997-1998, US-11 clonal lineage became predominant. The US-11 clonal lineage is generally resistant to chemical fungicides Metalaxyl, and could tolerate higher temperatures, and has wider the host range. There characteristics make late blight disease an important diseases of tomato in Taiwan. Planting resistant or tolerant varieties can be an effective means of controlling the disease. It could provide not only safe agricultural products, but also reduce the environmental pollution that may result from improper application of chemical pesticides. In recent years, the development of DNA-based markers technique has increase the efficiency of quantitative trait locus (QTL) mapping techniques to develop. Therefore, this study used resistant to Phytophthora infestans as a material, to evaluated phenotypic and genotypic data. The aim of this study was to identify quantitative trait loci (QTLs) for late blight resistance presence in the wild tomato Solanum pimpinellifolium accession L3708 by producing a F2:3 mapping population derived from L3708 and a susceptible cultivar T3224 (Solanum lycopersicum L.). The resistant mechanism was re-evaluated in L3708 by against Phytophthora infestans isolates in Taiwan. A total of two QTLs were mapped. A major QTL was detected between marker TG591 and marker CT220a on chromosome 9 by inoculation of the P. infestans isolate Pi39A. The chromosome 9 QTL co-located as previously documented Ph-3 gene. Furthermore, in addition to the Ph-3 gene, additional QTL was detected between marker SLP_0201 and SLP_0207 on chromosome 2 when a stronger virulent isolate Pi-733 was used for inoculation. Further fine mapping work was delimited Ph-3 gene in a 22kb chromosomal region comprising four annotated putative genes.