基因研究 英國白蠟樹對枯梢病抵抗力較強

Fears that almost all of Britain’s ash trees face annihilation may be exaggerated, according to a comprehensive genetic analysis of ash across the UK and Europe.

根據在英國和歐洲大陸對白蠟樹(ash tree)進行的全面遺傳分析，有關英國幾乎所有白蠟樹都面臨滅絕的擔心可能被誇大了。

The study, carried out by a collaboration of 12 academic research teams and published in Nature, found that British trees are more likely than their continental counterparts to carry genes that protect against ash dieback, a fungal infection with the potential to wipe out 90 per cent of the European ash population.

這項研究由12個學術研究團隊協同開展，結果發表於《自然》(Nature)雜誌。研究發現，相比歐洲大陸的白蠟樹，英國的白蠟樹更有可能攜帶抵禦白蠟樹枯梢病(ash dieback)的基因；這是一種真菌感染，有可能殺死90%的歐洲白蠟樹種羣。

“It’s an encouraging hint that things may not be as bad as we had feared,” said study leader Richard Buggs of Queen Mary University of London and Royal Botanic Gardens Kew.

“這是一個令人鼓舞的消息，表明事情可能不像我們此前擔心的那樣糟糕，”倫敦大學瑪麗皇后學院(Queen Mary University of London)和皇家植物園邱園(Royal Botanic Gardens Kew)的研究帶頭人理查德.巴格斯(Richard Buggs)表示。

“But these are preliminary indications and I wouldn’t want to see government policy on ash dieback shaped by the research until we have more evidence for the susceptibility of British trees.”

“但這些都是初步跡象，在我們有更多證據表明英國白蠟樹的易感性之前，我不想看到針對白蠟樹枯梢病的政府政策受到此項研究的影響。”

The encouraging news comes from the discovery of a link between reduced susceptibility to ash dieback and lower levels of plant chemicals called iridoid glycosides. Most British ash trees produce less of these compounds than continental ones, the genetic analysis suggests.

這一令人鼓舞的消息源於這樣一個發現：較低的白蠟樹枯梢病易感性與較低水平的植物化學物質“環烯醚萜苷類”(iridoid glycosides)之間存在關聯。遺傳分析似乎表明，相比歐洲大陸的白蠟樹，多數英國白蠟樹生成的這類化合物較少。

Mr Buggs said the findings might explain why ash dieback has not spread as rapidly in the UK as feared in 2012 when the fungus first arrived from continental Europe. “Most of our early models were based on the Danish experience,” he said.

巴格斯表示，這些研究結果可能解釋了爲什麼2012年白蠟樹枯梢病從歐洲大陸傳播至英國時，沒有像人們擔心的那樣快速傳播。“我們使用的多數初期模型都是基於丹麥的經驗，”他說。

The disease causes trees to lose their leaves and eventually die. It has killed millions of plants in eastern and northern Europe since reaching Poland in 1992. Young trees die fast while mature ash often take several years to succumb.

這種疾病會導致白蠟樹落葉，最終枯萎而死。自1992年傳播至波蘭以來，它已在東歐和北歐殺死了數以百萬計的白蠟樹。幼樹很快死亡，而成年白蠟樹往往在幾年後死亡。

“Plants use a vast range of chemicals to defend against fungal attack, and the primary objective [of the project] was to identify differences which could be used to screen young ash trees and choose the best ones for replanting,” said co-author Murray Grant of the University of Warwick. “Our findings underline the need for further research to ensure that we select ash trees resilient to present and future threats.”

“植物利用多種多樣的化學物質來抵禦真菌侵襲，（該項目的）主要目標是識別差異，以便篩選幼樹，挑選出最佳的樹進行補種，”研究報告聯名作者、華威大學(University of Warwick)的默裏.格蘭特(Murray Grant)表示。“我們的研究結果突顯了進一步研究的需要，以確保我們篩選出對當前乃至未來的威脅具有抵抗力的白蠟樹。”

While the genetic analysis is encouraging news for the fungal resistance of British ash, it may have a downside, too. Iridoid glycosides help to protect plants against insect pests, so low levels could make the British trees more vulnerable to the other big threat to European ash, a beetle called the emerald ash borer.

雖然遺傳分析在英國白蠟樹的真菌抗性上帶來了令人鼓舞的消息，但它也可能意味着一個弱點。環烯醚萜苷類有助於保護植物免受蟲害，因此這類化合物的含量較低可能使英國白蠟樹在另一大威脅——一種被稱爲白蠟窄吉丁(emerald ash borer)的甲蟲——面前更爲脆弱。

The beetle has devastated vast tracts of ash in North America and is spreading westward from Russia into Europe. Although emerald ash borer has not reached the UK, arboriculturists fear its arrival is just a matter of time.

這種甲蟲在北美摧毀了大量白蠟樹，並正從俄羅斯向西擴散，直撲歐洲。雖然白蠟窄吉丁尚未抵達英國，但樹木栽培者擔心，它們的到來只是一個時間問題。