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Genome of wild mandarin and domestication history of mandarin

First author:Lun Wang;Affiliations:Huazhong Agricultural University(華中農業大學):Wuhan,China

Corresponding author:Qiang Xu

Mandarin (Citrus reticulata) is one of the most important citrus crops worldwide. Its domestication is believed to occur in South China, which has been one of the cultivation centers for four millennia (四千年). We collected natural wild populations of mandarin around the Nanling region (南嶺地區) and cultivated landraces (栽培種) in the vicinity (附近). The citric acid (檸檬酸) level was dramatically reduced in cultivated mandarins. To understand the genetic basis of mandarin domestication, wede novoassembled a draft genome of wild mandarin and analyzed a set of 104 citrus genomes. The results showed that the Mangshan mandarin (莽山柑橘) is a primitive type and that two independent domestication events have occurred, resulting in two groups of cultivated mandarins (MD1 and MD2) in the North and South of the Nanling Mountains, respectively. Two bottlenecks (瓶頸) and two expansions of effective population size were identified for the MD1 group of cultivated mandarins. However, in the MD2 group, there was a long and continuous decrease in the population size. MD1 and MD2 mandarins showed different patterns of interspecific introgression from cultivated pummelo (柚) species. We identified a genomic region of high divergence in an aconitate hydratase (ACO; 烏頭酸水合酶) gene involved in the regulation of citrate content (檸檬酸含量), which was possibly under selection during the domestication of mandarin. This study provides concrete (實在的) genetic evidence for the geographical origin of extant wild mandarin populations and sheds light on the domestication and evolutionary history of mandarin.

柑橘是最重要的柑橘屬果樹作物。柑橘的馴化被認為發生在中國南方，這也是中國四千年的柑橘栽培中心。作者收集了柑橘在南嶺地區的自然群體和一些周邊的栽培種。在栽培種柑橘中檸檬酸的水平劇烈下降。為了理解柑橘馴化中的遺傳基礎，作者從頭組裝了一個野生柑橘的基因組，並分析了104個柑橘屬的基因組。結果表明莽山柑橘是原始類型，發生過兩次獨立的馴化事件，導致了兩個栽培種，MD1和MD2，分別分布在南嶺山區的南和北地區。在MD1群體中，鑒定到了兩次有效群體大小的群體瓶頸和群體擴張事件。然而，在MD2群體中，群體大小經歷了一次持久的衰減。MD1和MD2柑橘顯示了不同的來自柚子的種間基因滲入模式。作者鑒定了一個基因組高度分化區域，該區域在烏頭酸水合酶(ACO)基因上，而ACO基因參與了檸檬酸含量的調控，進而可能在柑橘馴化過程中經歷了選擇。本文的研究為現存野生柑橘群體的地理起源提供了實實在在的遺傳證據，同時也對柑橘的馴化和演化歷史提供了新的視野。

通訊：徐強(http://linx.hzau.edu.cn/szxx/zzjs/gsx/jiaoshou/201403/t20140305_37532.htm)

個人簡介：1998-2002年，華中農業大學，園藝學士；2002-2007年，華中農業大學，園藝博士；2009-2010年，美國康奈爾大學合作研究。

研究方向：柑橘果實品質調控機理研究；耐黃龍病基因發掘與耐病機理解析；基於基因組學的分子工具開發及輔助育種。

doi: https://doi.org/10.1016/j.molp.2018.06.001

Journal:Molecular Plant

First Published: 22 June, 2018

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