Genome of wild mandarin and domestication history of mandarin

First author: Lun Wang; Affiliations: Huazhong Agricultural University (中国华中农业大学): 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 (南岭地区) and cultivated landraces (栽培种) in the vicinity (附近). The citric acid (柠檬酸) level was dramatically reduced in cultivated mandarins. To understand the genetic basis of mandarin domestication, we de novo assembled 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 (瓶颈) 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; 乌头酸水合酶) gene involved in the regulation of citrate content (柠檬酸含量), which was possibly under selection during the domestication of mandarin. This study provides concrete (实在的) genetic evidence for the geographical origin of extant wild mandarin populations and sheds light on the domestication and evolutionary history of mandarin.

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柑橘是最重要的柑橘属果树作物。柑橘的驯化被认为发生在中国南方，这也是中国四千年的柑橘栽培中心。作者收集了柑橘在南岭地区的自然群体和一些周边的栽培种。在栽培种柑橘中柠檬酸的水平剧烈下降。为了理解柑橘驯化中的遗传基础，作者从头组装了一个野生柑橘的基因组，并分析了104个柑橘属的基因组。结果表明莽山柑橘是原始类型，发生过两次独立的驯化事件，导致了两个栽培种，MD1和MD2，分别分布在南岭山区的南和北地区。在MD1群体中，鉴定到了两次有效群体大小的群体瓶颈和群体扩张事件。然而，在MD2群体中，群体大小经历了一次持久的衰减。MD1和MD2柑橘显示了不同的来自柚子的种间基因渗入模式。作者鉴定了一个基因组高度分化区域，该区域在乌头酸水合酶(ACO)基因上，而ACO基因参与了柠檬酸含量的调控，进而可能在柑橘驯化过程中经历了选择。本文的研究为现存野生柑橘群体的地理起源提供了实实在在的遗传证据，同时也对柑橘的驯化和演化历史提供了新的视野。

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

个人简介：1998-2002年，华中农业大学，园艺学士；2002-2007年，华中农业大学，园艺博士；2009-2010年，美国康奈尔大学合作研究。

研究方向：柑橘果实品质调控机理研究；耐黄龙病基因发掘与耐病机理解析；基于基因组学的分子工具开发及辅助育种。

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

Journal: Molecular Plant

First Published: 22 June, 2018

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