三个多倍体猕猴桃基因组Survey分析及系统进化研究

周 嘉1,王飞飞1,2,仲伟敏1,齐 勇1,刘 青1,史斌斌1,张 晟1,牛歆雨2,郑乾明1,唐冬梅1*

1贵州省农业科学院果树科学研究所,贵阳 550006;2西藏农牧学院植物科学学院,西藏林芝 860000)

摘 要:【目的】全面了解多倍体猕猴桃种质资源的染色体倍性和基因组特征,并分析其在猕猴桃属植物中的系统进化关系,以期为多倍体猕猴桃全基因组组装提供参考。【方法】基于流式细胞术分析中华猕猴桃AcD2301(Actinidia chinensis)、软枣猕猴桃AcD2302(Actinidia arguta)、对萼猕猴桃AcD2303(Actinidia valvata)染色体倍性,利用Illumina二代测序平台开展基因组Survey分析,并基于SNP构建15种猕猴桃属植物系统进化树。【结果】中华猕猴桃AcD2301、软枣猕猴桃AcD2302、对萼猕猴桃AcD2303的染色体倍性分别为四倍体、四倍体、六倍体,与survey分析结果一致。Kmer 分析预测中华猕猴桃AcD2301、软枣猕猴桃AcD2302、对萼猕猴桃AcD2303 单套基因组大小分别约为626 Mb、668 Mb、585 Mb,杂合度为3.00%、3.30%、8.06%,重复序列比例为43.70%、45.30%、40.70%。系统进化树显示软枣猕猴桃与对萼猕猴桃亲缘关系较近,且均从中华猕猴桃独立进化而来。【结论】分析了中华猕猴桃AcD2301、软枣猕猴桃AcD2302、对萼猕猴桃AcD2303的染色体倍性、基因组大小和系统进化关系,为将来开展多倍体猕猴桃全基因组测序提供了参考,也为深入研究猕猴桃多倍化和系统进化提供了理论支持。

关键词:猕猴桃;基因组survey分析;基因组大小;系统进化

猕猴桃(Actinidia spp.)是猕猴桃科(Actinidiaceae)猕猴桃属(Actinidia Lindl.)植物,是20 世纪初开始人工驯化栽培的特色经济果树,由于果实风味独特、营养丰富、维生素C含量高等优点,被誉为水果之王且深受广大消费者青睐[1-2]。2024年联合国粮农组织FAO(https://www.fao.org/home/zh/)统计数据显示,截至2022 年世界猕猴桃采收面积28.61 万hm2,产量429.15万t,是全球性重要的水果产业。其中中国猕猴桃产量约占世界猕猴桃总产量的2/3,已成为中国重要的特色水果产业之一。猕猴桃为功能性雌雄异株植物,起源和分布中心均在中国,是广大山区常见的一种水果,生长在路旁、林中、水沟边、灌丛中,自然状态下存在着广泛的种间和种内杂交现象,造成了猕猴桃属植物复杂的形态结构变异。在猕猴桃属植物中,多倍化现象普遍存在,例如已知的主栽品种中华猕猴桃红阳、软枣猕猴桃魁绿、美味猕猴桃贵长分别为二倍体、四倍体、六倍体。此外,猕猴桃种内染色体倍性变异也较为常见,不同倍性材料在生态适应[3]、抗逆[4]及果实品质[5]方面存在显著差异。猕猴桃多倍化是适应环境变化保护自身种群发展的进化,不仅使猕猴桃的染色体数目加倍,还影响其基因组的结构和功能,从而丰富猕猴桃遗传多样性[6]

随着基因组学时代的到来和发展,测序成本不断降低,高通量测序已被广泛应用于植物基因组测序中。在猕猴桃属植物中,中华猕猴桃(Actinidia chinensis[7]、毛花猕猴桃(Actinidia eriantha[8]、阔叶猕猴桃(Actinidia latifolia[9]、山梨猕猴桃(Actinidia rufa[10]、软枣猕猴桃(Actinidia arguta[11]、长叶猕猴桃(Actinidia hemsleyana[12]、葛枣猕猴桃(Actinidia polygama[10]等基因组已有报道,为其他猕猴桃属植物的全基因组测序、重要性状解析和遗传改良等工作奠定了基础[13]。然而中华猕猴桃、美味猕猴桃、软枣猕猴桃等主要栽培利用的物种普遍存在多倍化的现象,尽管不同倍性种质的基因组信息有共性之处,但多倍体猕猴桃的全基因组信息仍有待解析[14-15]。此外,对萼猕猴桃作为新型猕猴桃砧木,具备较强的抗涝、抗寒、抗病能力,在产区中也已经得到较大规模的推广[16],但缺乏其基因组信息,阻碍了对其重要抗逆性状的解析。因此,考察中华猕猴桃、软枣猕猴桃、对萼猕猴桃的倍性及基因组信息对后续指导多倍体基因组的组装和辅助其他相关研究具有十分重要的意义。

笔者在本研究中选取野生种质中华猕猴桃AcD2301(Actinidia chinensis)、软枣猕猴桃AcD2302(Actinidia arguta)、对萼猕猴桃AcD2303(Actinidia valvata)进行多倍体猕猴桃基因组Survey 分析及系统进化研究,通过流式细胞术、K-mer分析和系统进化树构建,进行染色体倍性、物种杂合率、基因组重复序列比例和基因组大小的评估及系统进化关系研究,以期为多倍体猕猴桃全基因组组装提供参考,也可为深入研究猕猴桃多倍化和系统进化提供理论支持。

1 材料和方法

1.1 试验材料

试验材料中华猕猴桃AcD2301、软枣猕猴桃AcD2302、对萼猕猴桃AcD2303 均为野生资源(表1),保存于贵州省农业科学院果树科学研究所百宜落叶果树试验基地。试验样品采集,剪取顶端幼嫩叶片,液氮速冻后置于-80 ℃超低温冰箱保存备用。

表1 样品采集信息
Table 1 Sample collection information

样品名称Sample name中华猕猴桃AcD2301 Actinidia chinensis AcD2301软枣猕猴桃AcD2302 Actinidia arguta AcD2302对萼猕猴桃AcD2303 Actinidia valvata AcD2303性别Sexuality雌Female雌Female两性花Bisexual flower采样时间Sampling time 2023年5月May,2023 2023年5月May,2023 2023年5月May,2023采样地点Sampling site贵州省贵阳市Guiyang,Guizhou贵州省贵阳市Guiyang,Guizhou贵州省贵阳市Guiyang,Guizhou

1.2 试验方法

1.2.1 染色体倍性检测 以二倍体红阳猕猴桃(Actinidia chinensis‘Hongyang’,2n=58)为内参样本,采用流式细胞术进行染色体倍性检测[17]。分别称取AcD2301、AcD2302和AcD2303新鲜顶端叶片0.2 g,置于培养皿中,用CyStain UV Precise P 试剂盒进行细胞核裂解,提取完成后用50 μm Celltrics滤网过滤至样品管中,加入DAPI荧光染液避光染色2 min后在CyFlow Space 流式细胞仪上进行流式细胞术测试,用FloMax软件分析核悬浮液。

1.2.2 DNA 提取及测序 采用CTAB 法提取猕猴桃基因组总DNA,并通过0.8%琼脂糖凝胶电泳检测DNA 提取质量,同时采用紫外分光光度计对DNA进行定量。利用第二代测序技术Illumina NovaSeq测序平台对样本文库进行双末端测序。采用fastp[18]等软件查看碱基质量分布、Reads平均错误率分布、Reads 测序碱基含量分布,原始数据过滤接头和低质量reads 获得高质量序列,并与核酸库进行比对,排除外源物种污染。

1.2.3 基因组Survey 分析 高质量测序数据基于jellyfish(version 2.3.0)软件设置K-mer为19生成Kmer 频数表和频率直方图,统计总K-mer数、唯一Kmer 数等,并运用GenomeScope 2 工具进行基因组大小、杂合度和重复序列比例的估计[19-20]

1.2.4 基于SNP的系统进化树构建 基于自测数据(AcD2301、AcD2302、AcD2303)和公共数据库(NGDC、NCBI)下载部分已公布的猕猴桃二代测序数据(表2),在贵州省农业科学院果树科学研究所生物信息学分析平台进行系统进化分析,与参考基因组红阳v4.0[21]进行比对,利用GATK软件[22]进行SNP calling(仅保留二等位基因),用fastTree软件中的Maximum likelihood算法构建系统进化树,并将树文件进行可视化处理。

表2 猕猴桃属植物种名
Table 2 Kiwifruit plant species name and Latin name

注:NGDC.国家生物信息中心(中国);NCBI.美国国家生物技术信息中心(美国)。
Note: NGDC.National Center for Biotechnology Information (China);NCBI.National Center for Biotechnology Information(USA).

编号Numbering AcD2301种名Species name中华猕猴桃(Actinidia chinensis)AcD2302软枣猕猴桃(Actinidia arguta)AcD2303对萼猕猴桃(Actinidia valvata)CRR635714数据来源data sources自测数据Self-test data自测数据Self-test data自测数据Self-test data NGDC CRR635715 SRR3543582 NGDC NCBI NCBI NCBI NCBI NCBI NCBI NCBI NCBI NCBI NCBI SRR18177732 SRR3723918 SRR3705798 SRR3705797 SRR3723917 SRR3407085 SRR3474219 SRR3474216 SRR3474220中华猕猴桃东红(Actinidia chinensis‘Donghong’)阔叶猕猴桃(Actinidia latifolia)美味猕猴桃(Actinidia chinensis var.deliciosa)湖北猕猴桃(Actinidia hubeiensis)浙江猕猴桃(Actinidia zhejiangensis)黄毛猕猴桃(Actinidia fulvicoma)毛花猕猴桃(Actinidia eriantha)山梨猕猴桃(Actinidia rufa)软枣猕猴桃(Actinidia arguta)葛枣猕猴桃(Actinidia polygama)大籽猕猴桃(Actinidia macrosperma)对萼猕猴桃(Actinidia valvata)

2 结果与分析

2.1 猕猴桃染色体倍性分析

以二倍体红阳猕猴桃(Actinidia chinensis var.‘Hongyang’,2n=58)为内参样本,分析3份猕猴桃样品的倍性,图1 展示为猕猴桃多倍体样品倍性的流式直方图。其流式直方图中横坐标代表荧光强度,纵坐标代表细胞数量,荧光强度与DNA 含量成正比,即峰值的位置反映测试样品的倍性。根据内参物种二倍体红阳猕猴桃(图1-A)的峰值比较,AcD2301(图1-B)和AcD2302(图1-C)的染色体倍性均为四倍体,而AcD2303(图1-D)染色体倍性为六倍体,流式细胞术测得染色体倍性结果与后续全基因组测序结果一致,图中杂峰可能是部分细胞核降解造成的。

图1 猕猴桃多倍体流式直方图
Fig.1 Kiwi polyploid flow cytometry histogram

2.2 猕猴桃基因组测序及质控

通过二代Illumina NovaSeq 测序平台对AcD2301、AcD2302 和AcD2303 基因DNA 进行测序,分别获得162.91 Gb、139.74 Gb和142.44 Gb原始测序数据,经过过滤后分别获得160.64 Gb、138.16 Gb和140.73 Gb高质量测序数据;测序的质量评估结果显示,AcD2301 的Q20、Q30 值分别为96.95%、91.91%,AcD2302 的Q20、Q30 值分别为97.09%、92.07%,AcD2303 的Q20、Q30 值分别为96.80%、91.43%,表明基因组数据可靠,可用于后续分析。AcD2301、AcD2302和AcD2303基因GC含量分别约为37.20%、36.77%和36.15%(表3)。AcD2301(图2-A、图3-A)、AcD2302(图2-B、图3-B)和AcD2303(图2-C、图3-C)基因组中大部分测序数据质量值均大于35(图2),其碱基错误率均小于0.045(图3),表明其基因组测序的Reads质量较高,测序结果可信度较高。

图2 单碱基质量分布
Fig.2 Single base quality distribution

图3 Reads 平均错误率分布
Fig.3 Distribution of average error rate of reads

表3 基因组测序数据统计
Table 3 Statistics of genome sequencing data

样品Sample总Reads数The total number of reads总碱基数Total number of bases/bp过滤后Reads数Number of reads after filtering过滤后碱基Bases after filtering/bp Q20 rate/%Q30 rate/%GC/%AcD2301 1 078 845 806925 411 346943 316 252 162 905 716 706139 737 113 246142 440 754 052 1 067 883 632916 913 380934 022 544 160 639 029 587138 162 662 210140 726 147 170 96.9597.0996.80 91.9192.0791.43 37.2036.7736.15 AcD2302 AcD2303

2.3 猕猴桃基因组测序数据与NT数据库比对

进一步从AcD2301、AcD2302 和AcD2303 基因组测序数据中随机抽取10 000 条Reads 数据使用Blast 软件与核酸库(NT 库)进行比对,挑选最优比对结果按物种统计(表4),结果显示随机选取Reads均能比对上猕猴桃属植物基因组,表明此次测序的基因组数据不存在污染,部分样本与核酸库比对率较低的原因与取样少有关。

表4 NT 比对结果统计
Table 4 NT comparison results statistics

物种名Species name中华猕猴桃Actinidia chinensis茶树Camellia sinensis软枣猕猴桃Actinidia arguta小叶猕猴桃Actinidia lanceolata黑蕊猕猴桃Actinidia melanandra对萼猕猴桃Actinidia valvata山梨猕猴桃Actinidia rufa君迁子Diospyros lotus葛枣猕猴桃Actinidia polygama Reads数/比率The number of reads/Ratio AcD2301 865/8.65 214/2.14-138/1.38 85/0.85-68/0.68 45/0.45-AcD2302 636/6.36 188/1.88 296/2.96 144/1.44--101/1.01 46/0.46-AcD2303 445/4.45 183/1.83-108/1.08-101/1.01 67/0.67-61/0.61

2.4 猕猴桃基因组survey分析

高质量数据通过K-mer 分析,预估物种基因组大小,并对物种的杂合度、重复情况进行分析。通过对质控后的猕猴桃基因组数据进行K-mer 分析(图4、表5),可知AcD2301(图4-A)预估单套基因组大小为626 Mb,杂合度为3.00%,重复序列比例为43.70%;AcD2302(图4-B)预估单套基因组大小为668 Mb,杂合度为3.30%,重复序列比例为45.30%;AcD2303(图4-C)预估单套基因组大小为585 Mb,杂合度为8.06%,重复序列比例为40.70%。基于猕猴桃基因组Survey数据分析得出AcD2301(图4-A)同源四倍体支持率为97%,AcD2302(图4-B)同源四倍体支持率为96.7%。

图4 K-mer 分布曲线
Fig.4 K-mer distribution curve

表5 基于19-kmer 基因组信息估计统计
Table 5 Estimated statistics based on 19-kmer genome information

类型Type K个碱基的序列Sequence of K bases K-mer分布图的峰值The peak of K-mer distribution map杂合度Heterozygosity/%基因组大小Genome size/Mb重复序列比例Repeat sequence ratio/%使用数据量Amount of data used/G数据量乘数Quantity of data multiplier AcD2301 19 AcD2302 19 AcD2303 19 104 85.8 67.6 3.00 626 43.70 3.30 668 45.30 8.06 585 40.7 160.6 138 141 256 206 240

2.5 猕猴桃属植物进化树分析

为分析猕猴桃属植物的进化关系,筛选了已报道的中华猕猴桃东红、美味猕猴桃和湖北猕猴桃等15种猕猴桃属植物的二代测序数据中的SNP序列,采用Maximum likelihood算法构建系统进化树。该系统进化树显示(图5),15 种猕猴桃属植物分为三大进化分枝,且均得到了较好的支持,其中中华猕猴桃AcD2301为一个独立进化枝,东红猕猴桃为另一个独立进化枝,其余13 种猕猴桃组成一个进化枝。在第三个进化分枝中的美味猕猴桃为一个小进化枝,其余12种猕猴桃组成一个小进化分枝。对于后者湖北猕猴桃单独一组;其余11 种猕猴桃为一组,其中净果组的6种猕猴桃(软枣猕猴桃AcD2302、软枣猕猴桃、葛枣猕猴桃、大籽猕猴桃、对萼猕猴桃AcD2303、对萼猕猴桃)聚为一个小进化分枝,而其余分枝的9种猕猴桃均为斑果组。

图5 猕猴桃属植物系统进化树
Fig.5 The phylogenetic tree of kiwifruit plants

系统进化树构建中下载并使用已公布的猕猴桃二代测序数据有东红猕猴桃、阔叶猕猴桃(https://ngdc.cncb.ac.cn);美味猕猴桃、湖北猕猴桃、浙江猕猴桃、黄毛猕猴桃、毛花猕猴桃、山梨猕猴桃、软枣猕猴桃、葛枣猕猴桃、大籽猕猴桃、对萼猕猴桃(https://www.ncbi.nlm.nih.gov)。
In the construction of phylogenetic tree,the published next-generation sequencing data of kiwifruit were downloaded and used,including Actinidia chinensis‘Donghong’,Actinidia latifolia (https://ngdc.cncb.ac.cn);Actinidia chinensis var.deliciosa,Actinidia hubeiensis,Actinidia zhejiangensis,Actinidia fulvicoma,Actinidia eriantha,Actinidia rufa,Actinidia arguta,Actinidia polygama,Actinidia macrosperma, and Actinidia valvata (https://www.ncbi.nlm.nih.gov/).

3 讨 论

多倍化是推动植物遗传多样性和适应环境变化的重要机制之一,在植物中广泛存在,其中猕猴桃属植物中多倍化现象非常普遍。猕猴桃多倍化表现为体细胞均增大、果形更加圆润饱满,叶片颜色更深、表皮毛被明显增多、产量高、抗性强等特征[3-5]。尽管以往的研究已经从很大程度上揭示了猕猴桃属物种的基因组信息以及主要倍性,但仍有部分物种尚未明确。本研究中就基于流式细胞术分析AcD2301、AcD2302、AcD2303的染色体倍性分别为四倍体、四倍体和六倍体。而基于猕猴桃基因组Survey 数据分析所得AcD2301 同源四倍体支持率为97%,AcD2302 同源四倍体支持率为96.7%,与上述结果基本一致。以上工作为进一步丰富猕猴桃物种基因组奠定了基础。

基于测序技术解析全基因组信息,为植物起源、进化、生殖、发育、抗性和性别调控等研究提供了基础。不同种类的植物基因组大小相差很大,根据目前已经公布的基因组数据中梅溪蕨(Tmesipteris oblanceolata)的基因组大小约160.45 Gb,而旋刺草(Genlisea aurea)的基因组大小仅为约0.063 6 Gb,相差约2500倍[23]。目前主要采用流式细胞术和高通量测序技术等方法评估植物的基因组大小,例如在四数九里香[24]、白及[25]、荆芥[26]等多种植物基因组大小特征评估中都有应用。流式细胞术是通过测量细胞中DNA与荧光染料结合后发出的荧光信号强度,来间接预估基因组大小的相对值,而基因组Survey分析是利用高通量测序技术对植物基因组进行测序和直接获取基因组大小等信息的测序技术,这两种技术结合起来评估基因组大小和特征相对可靠[27]。已报道猕猴桃属植物的基因组大小通常在600 Mb左右,中华猕猴桃为610.1 Mb[7],毛花猕猴桃为619.3 Mb和611.7 Mb[8]等,本研究结果所揭示的单套基因组大小较为相近,AcD2301 为626 Mb、AcD2302 为668 Mb、AcD2303 为585 Mb,均都在600 Mb 左右,但基因组具体大小又取决于不同的种质资源。

基因组学研究还可以揭示物种的遗传多样性、基因组演化历程以及基因功能等,通过构建系统进化树可以直观地展现亲缘关系和进化历程[28]。已有研究通过UPGMA聚类分析得到星毛组的中华猕猴桃与净果组的软枣猕猴桃亲缘关系较远[29],并且与净果组的对萼猕猴桃亲缘关系也较远[30],由此推测同为净果组的软枣猕猴桃和对萼猕猴桃亲缘关系较近,并均与星毛组的中华猕猴桃亲缘关系较远。本研究中构建的猕猴桃属植物系统进化树,证明了软枣猕猴桃AcD2302 与对萼猕猴桃AcD2303 亲缘关系较近,且均与中华猕猴桃AcD2301独立进化而来的结果一致,为阐明物种进化关系及基因组的内在结构奠定了基础。

4 结 论

中华猕猴桃AcD2301、软枣猕猴桃AcD2302、对萼猕猴桃AcD2303 的染色体倍性分别为四倍体、四倍体和六倍体,与全基因组测序预估结果一致;基于全基因组Survey 分析预测基因组大小分别为626 Mb、668 Mb、585 Mb,杂合度为3.00%、3.30%、8.06%,重复序列比例为43.70%、45.30%、40.7%。SNP 系统进化树显示软枣猕猴桃AcD2302 与对萼猕猴桃AcD2303亲缘关系较近,且均与中华猕猴桃AcD2301独立进化而来。

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Survey analysis and phylogenetic study of three polyploid kiwifruit genomes

ZHOU Jia1, WANG Feifei1,2, ZHONG Weimin1, QI Yong1, LIU Qing1, SHI Binbin1, ZHANG Sheng1,NIU Xinyu2,ZHENG Qianming1,TANG Dongmei1*
(1Guizhou Fruit Science Research Institute, Guizhou Academy of Agricultural Sciences, Guiyang 550006, Guizhou, China;2College of Plant Sciences,Tibet Agricultural and Animal Husbandry College,Nyingchi 860000,Xizang,China)

Abstract: 【Objective】Plant polyploidization is the evolution of adaption to environmental changes and protection of their own population development.The polyploidization of kiwifruit could double its chromosome number and affect the structure and function of its genome,thereby enriching the genetic diversity of the species.The study aimed to comprehensively understand the chromosomal ploidy and genomic characteristics of polyploid kiwifruit germplasm resources, and analyze their systematic evolutionary relationships in kiwifruit.【Methods】This study analyzed the chromosome ploidy of AcD2301(Actinidia chinensis), AcD2302 (A.arguta) and AcD2303 (A.valvata) with reference to the diploid A.chinensis‘Hongyang’.The samples were analyzed by flow cytometry on the CyFlow Space flow cytometer after being lysed by CyStar UV Precise P kit and dyed by DAPI fluorescent dye in the dark.The total genomic DNA of kiwifruit was extracted by CTAB method,and then electrophoresis was conducted with 0.8%agarose gel.The DNA quality was detected with UV spectrophotometer.The secondgeneration sequencing technology Illumina NovaSeq sequencing platform was used to perform double end sequencing on the sample library.The softwares such as FastP were used to view the distribution of base quality, average error rate distribution of reads, and base content distribution of reads sequencing.The raw data with adapters and low-quality reads were filtered to obtain high-quality sequences,and the sequences were compared with nucleic acid databases.The high quality sequencing data was generated using Jellyfish (version 2.3.0) software k-mer19 to generate K-mer frequency tables, and genome size,heterozygosity, and repeatability were estimated using the GenomeScope 2.The next-generation sequencing data of kiwifruit,published in the NGDC and NCBI databases,were compared with the reference genome A.chinensis Hongyang v4.0.The SNP calling was performed using GATK software, and the Maximum likelihood algorithm in fast Tree software was used to construct phylogenetic trees of the 15 kiwifruit species, including A.chinensis,A.arguta and A.valvata.【Results】The samples were subjected to flow cytometry analysis, and the peak values of the diploid Hongyang kiwifruit were compared with the reference species.The chromosome ploidy of the AcD2301 and AcD2302 were both tetraploid, while the chromosome ploidy of the AcD2303 was hexaploid.The subsequent genome survey analysis results were consistent with this.The AcD2301,AcD2302 and AcD2303 gene DNA were sequenced by the Illumina NovaSeq sequencing platform.The sequencing yielded raw data of 162.91 Gb,139.74 Gb, and 142.44 Gb, followed by filtering to obtain high-quality data of 160.64 Gb, 138.16 Gb,and 140.73 Gb.The sequencing quality assessment showed that the Q20 and Q30 values of the AcD2301 were 96.95% and 91.91%, respectively.The Q20 and Q30 values of the AcD2302 were 97.09%and 92.07%,respectively.The Q20 and Q30 values of the AcD2303 were 96.80%and 91.43%,respectively;The GC contents were approximately 37.20%,36.77%,and 36.15%,respectively.The sequencing data quality values were all greater than 35, and the base error rates were all less than 0.045,indicating that the genome reads had high quality and could be used for subsequent analysis.The reads from the sequencing data of the AcD2301,AcD2302, and AcD2303 were randomly selected and compared with the nucleic acid library(NT library).The results showed that all the randomly selected reads could be compared with the genome of kiwifruit plants, indicating that there was no contamination in the sequencing data.Through K-mer analysis of the kiwifruit genome data after quality control,the genome size of the AcD2301 was estimated to be 626 Mb, heterozygosity to be 3.00%, and repeat sequence ratio to be 43.70%; The estimated size of the AcD2302 genome was 668 Mb, with a heterozygosity of 3.30%and a repeat sequence ratio of 45.30%;The estimated genome size of the AcD2303 was 585 Mb,with a heterozygosity of 8.06%and a repeat sequence ratio of 40.70%.In addition,the support rates for homologous tetraploids of the AcD2301 and AcD2302 were 97% and 96.7%, respectively.To analyze the evolutionary relationship of kiwifruit plants,the SNP sequences were screened from the second-generation sequencing data of the 15 kiwifruit, including the AcD2301,AcD2302, and AcD2303.The Maximum likelihood algorithm was used to construct a phylogenetic tree.The results showed that the 15 kiwifruit plants were divided into three major evolutionary branches, with Actinidia chinensis AcD2301 as an independent branch, Actinidia chinensis‘Donghong’as another independent branch,and the remaining 13 kiwifruit species as an evolutionary branch.Actinidia chinensis var. deliciosa in the third evolutionary branch was a small evolutionary branch, while the other 12 kiwifruit species formed a small evolutionary branch.For the latter,Actinidia hubeiensis was a separate group; The remaining 11 kiwifruit species were grouped together, and the 6 kiwifruit species in the net fruit group were clustered into a small evolutionary branch,while the 9 kiwifruit species in the remaining branches were all part of the spotted fruit group.From this,it could be seen that the AcD2302,which belonged to the net fruit group, was closely related to the AcD2303, and both had evolved independently from the AcD2301 in the spotted fruit group.【Conclusion】The chromosome ploidy, genome size, and phylogenetic relationships of the AcD2301,AcD2302 and AcD2303 were analyzed, which could provide reference for the whole genome sequencing of the polyploid kiwifruit in the future.

Key words: Kiwifruit;Genome survey analysis;Genome size;System evolution

中图分类号:S663.4

文献标志码:A

文章编号:1009-9980(2024)11-2214-10

DOI: 10.13925/j.cnki.gsxb.20240477

收稿日期:2024-09-23

接受日期:2024-10-31

基金项目:黔科合支撑[2023]一般045;黔果树所青年基金[2023]4号;国家现代农业产业技术体系项目(CARS-26);筑科合同[2023]2-3号;黔科合重大专项(字[2024]026)

作者简介:周嘉,助理研究员,硕士,主要从事猕猴桃遗传育种研究。E-mail:zhoujia4301@qq.com

*通信作者 Author for correspondence.E-mail:89368775@qq.com