劉秀云,李 慧,2,劉志國,趙 錦,劉孟軍,4
(1河北農(nóng)業(yè)大學(xué)/中國棗研究中心,河北保定 071001;2寧夏農(nóng)林科學(xué)院種質(zhì)資源研究所,寧夏銀川 750002;3河北農(nóng)業(yè)大學(xué)生命科學(xué)學(xué)院,河北保定 071000;4北京林果業(yè)生態(tài)環(huán)境功能提升協(xié)同創(chuàng)新中心,北京 102206)
基于SSR標(biāo)記的255個(gè)棗品種親緣關(guān)系和群體遺傳結(jié)構(gòu)分析
劉秀云1,李 慧1,2,劉志國1,趙 錦3,劉孟軍1,4
(1河北農(nóng)業(yè)大學(xué)/中國棗研究中心,河北保定 071001;2寧夏農(nóng)林科學(xué)院種質(zhì)資源研究所,寧夏銀川 750002;3河北農(nóng)業(yè)大學(xué)生命科學(xué)學(xué)院,河北保定 071000;4北京林果業(yè)生態(tài)環(huán)境功能提升協(xié)同創(chuàng)新中心,北京 102206)
【目的】棗原產(chǎn)中國,種質(zhì)資源豐富。對來自中國22個(gè)省區(qū)不同用途的255個(gè)棗品種進(jìn)行SSR分析,揭示這些不同產(chǎn)地來源的棗種質(zhì)資源之間的親緣關(guān)系和群體遺傳結(jié)構(gòu),為棗種質(zhì)資源的科學(xué)管理和分子標(biāo)記輔助育種提供參考?!痉椒ā坷酶牧糃TAB提取供試棗種質(zhì)的基因組DNA,以前期棗基因組測序挖掘出的SSR引物為基礎(chǔ),進(jìn)行高效率引物篩選,并利用SSR分子標(biāo)記技術(shù)對255份棗種質(zhì)資源的基因組DNA進(jìn)行PCR擴(kuò)增,然后利用8%聚丙烯酰胺凝膠電泳分離,銀染后顯色。根據(jù)條帶有無統(tǒng)計(jì)數(shù)據(jù),計(jì)算出多態(tài)性位點(diǎn)百分率(PIC),用NTSYS軟件進(jìn)行UPGMA聚類分析;利用Structure軟件分析群體遺傳結(jié)構(gòu),計(jì)算出最適群體數(shù)目,構(gòu)建遺傳結(jié)構(gòu)圖。【結(jié)果】從64對SSR引物中篩選出23對高效率SSR引物,在供試材料中共檢測出117個(gè)多態(tài)性位點(diǎn),各引物擴(kuò)增的多態(tài)性位點(diǎn)數(shù)為2—10條,每對引物平均擴(kuò)增多態(tài)位點(diǎn)數(shù)為5.09個(gè),PIC值變幅為0.359—0.727,平均為0.548,這些多態(tài)性引物可應(yīng)用到其他棗種質(zhì)資源的研究中;建立了只需1—2個(gè)標(biāo)記就可鑒別出來的部分棗品種的SSR指紋,可用于這些品種的快速分子鑒定;255個(gè)棗品種的聚類分析將所有棗品種分為15個(gè)亞類,包括4個(gè)大類和11個(gè)小類,不同品種間的相似系數(shù)范圍0.71—1.00,其中北京花生棗單獨(dú)聚為一類,與其他棗品種關(guān)系較遠(yuǎn);‘奉節(jié)雞蛋棗’和‘溆浦雞蛋棗’、‘陜西奶棗’和‘天津大馬牙棗’的相似系數(shù)均為 1.00;結(jié)合聚類圖、供試品種的用途和原產(chǎn)地分析,不同棗品種間的親緣關(guān)系與品種原產(chǎn)地有一定相關(guān)性,但和品種用途沒有顯著相關(guān)性。群體結(jié)構(gòu)分析中,通過繪制K與ΔK的關(guān)系圖,K=15時(shí),ΔK最大,據(jù)此將255個(gè)棗品種也同樣劃分為15個(gè)群體,與聚類分析結(jié)果基本一致;進(jìn)一步分析表明,各群體中大部分品種血緣關(guān)系比較單一,較少品種含有其他類群的遺傳成分??傮w看,山西或陜西的棗品種出現(xiàn)在絕大部分居群中,說明這兩個(gè)省的資源在不同群體間的基因交流中發(fā)揮了重要作用;南方栽培區(qū)域中來自湖南的棗品種形成了相對獨(dú)立的居群,可能是其起源相對單一,且在長期栽培過程中和其他產(chǎn)地棗品種間基因交流較少所致。上述結(jié)果表明,供試棗品種中與來源區(qū)域相關(guān)性明顯的品種由相同地域內(nèi)棗品種演化而來,而另一部分與來源產(chǎn)地相關(guān)性不明顯的品種則是由不同區(qū)域間品種經(jīng)過頻繁的基因交流和重組選育而來,融合了不同區(qū)域品種的特點(diǎn),從而沒有了明顯的區(qū)域特征?!窘Y(jié)論】不同地理環(huán)境在棗品種的群體進(jìn)化中發(fā)揮了較重要的作用,影響了不同產(chǎn)地間棗種質(zhì)資源的遺傳結(jié)構(gòu)組成。
棗;SSR分子標(biāo)記;產(chǎn)地;親緣關(guān)系;遺傳結(jié)構(gòu)
【研究意義】棗(Ziziphus jujuba Mill.)原產(chǎn)中國,栽培歷史悠久,遺傳變異豐富,“同物異名”和“同名異物”現(xiàn)象較為突出。采用傳統(tǒng)的形態(tài)學(xué)鑒定,費(fèi)時(shí)費(fèi)力,并且難以準(zhǔn)確的鑒定性狀相似的品種,而利用分子標(biāo)記構(gòu)建棗品種指紋圖譜并進(jìn)行遺傳結(jié)構(gòu)分析,有助于棗品種鑒定、遺傳進(jìn)化分析和分子輔助育種等研究?!厩叭搜芯窟M(jìn)展】RAPD(random amplified polymorphic DNA)、AFLP(amplified fragment length polymorphism)等分子標(biāo)記曾被成功用于棗的指紋圖譜構(gòu)建和親緣關(guān)系分析。趙錦等[1]對棗樹品種、品系及其近緣種進(jìn)行了RAPD分析,喬勇等[2]利用AFLP技術(shù)對21個(gè)棗品種進(jìn)行了分析,上述研究中供試材料的聚類結(jié)果與傳統(tǒng)觀點(diǎn)基本一致。近年來,SSR(simple sequence repeat)和SNP(single nucleotide polymorphisms)在國際植物新品種權(quán)保護(hù)聯(lián)盟(UPOV)的BMT分子測試指南中被確定為構(gòu)建DNA指紋數(shù)據(jù)庫的標(biāo)準(zhǔn)標(biāo)記方法。由于SSR標(biāo)記操作簡單,已成為當(dāng)前各種作物建庫的首選標(biāo)記[3]。SSR是由1—6個(gè)堿基對組成的簡單序列重復(fù),又稱微衛(wèi)星DNA,已經(jīng)被應(yīng)用在葡萄、獼猴桃、杏、蘋果等果樹上進(jìn)行遺傳多樣性分析[4-7]。2012年,麻麗穎等[8]利用12對SSR引物也構(gòu)建了 36份棗品種的指紋圖譜。遺傳結(jié)構(gòu)分析研究已在蘋果[9-10]、梨[11]、杏[12-16]、毛櫻桃[17]、楊梅[18]、荔枝[19]、芒果[20]、獼猴桃[21]、核桃[22-23]、石榴[24]、桃[25]中開展。在棗樹研究中,李海濤[26]利用ISSR標(biāo)記進(jìn)行研究的結(jié)果表明,河南棗主栽品種與灰棗的總?cè)后w間分化程度較高,群體間基因交流較少,基因流可防止由遺傳漂變引起的群體間的遺傳分化;殷曉[27]利用ISSR標(biāo)記對237份棗種質(zhì)的遺傳多樣性進(jìn)行了分析,結(jié)果表明黃河沿岸棗群體的雜合程度為重度雜合,遺傳多樣性豐富,變異程度較高,趨向遠(yuǎn)緣雜交?!颈狙芯壳腥朦c(diǎn)】目前尚未有利用SSR技術(shù)對大規(guī)模棗種質(zhì)材料進(jìn)行遺傳結(jié)構(gòu)分析的報(bào)道,因此,在前人研究基礎(chǔ)上,利用前期基于棗基因組測序開發(fā)的SSR引物[28],對來自全國22個(gè)省區(qū)主產(chǎn)地的255份棗種質(zhì)進(jìn)行更廣范圍的遺傳多樣性及群體結(jié)構(gòu)研究?!緮M解決的關(guān)鍵問題】分析中國棗種質(zhì)資源的起源,探討其遺傳多樣性水平和遺傳結(jié)構(gòu),為指紋圖譜構(gòu)建和分子輔助育種提供理論依據(jù)。
試驗(yàn)于2015年在河北農(nóng)業(yè)大學(xué)進(jìn)行。
1.1材料
選取來自全國22個(gè)省區(qū)及主產(chǎn)地的255個(gè)棗樹品種,供試品種信息詳見表1。所有品種材料均采自山西太谷國家棗種質(zhì)資源圃,于2013年6月采集供試材料的新鮮幼嫩葉片,置于冰盒中帶回實(shí)驗(yàn)室,轉(zhuǎn)入-20℃冰箱貯藏,以備提取基因組DNA。
1.2方法
基因組DNA提取方法按照肖京[29]的方法進(jìn)行。
SSR引物為筆者實(shí)驗(yàn)室前期開發(fā)出的引物[28],SSR擴(kuò)增在BIO-RAD公司生產(chǎn)BS97 MyCycler型的PCR儀上進(jìn)行,反應(yīng)體系(12.5 μL)中含有0.5 μL基因組DNA(含量10—25 ng),6.3 μL Taq MasterMix(天根),正向引物和反向引物各0.5 μL,4.7 μL ddH2O。SSR擴(kuò)增程序:94℃預(yù)變性3 min,然后94℃變性30 s,57℃退火30 s,72℃延伸30 s,27個(gè)循環(huán),最后72℃延伸7 min。擴(kuò)增產(chǎn)物用10%聚丙烯酰胺凝膠進(jìn)行分離,銀染技術(shù)檢測。
1.3統(tǒng)計(jì)分析
依據(jù)SSR擴(kuò)增產(chǎn)物在電泳凝膠上的相對位置,對擴(kuò)增條帶進(jìn)行記錄,分別以“1”和“0”表示同一位置譜帶的有無,建立原始數(shù)據(jù)陣,用NTSYS-pc 2.10e軟件[30]進(jìn)行后續(xù)分析。
計(jì)算多態(tài)性位點(diǎn)百分率P(%)=(k/n)×100,其中k為多態(tài)位點(diǎn)數(shù),n為所測位點(diǎn)總數(shù)。SSR位點(diǎn)的多態(tài)性信息量(poly-morphism information content,PIC)按如下計(jì)算公式進(jìn)行計(jì)算:PIC=1-ΣPi2,式中Pi表示第i個(gè)等位位點(diǎn)出現(xiàn)的頻率[31]。
利用NTSYS中的Qualitative date模塊計(jì)算任意兩個(gè)品種間的相似系數(shù)(GS)。其計(jì)算公式為GS=2Nij/ (Ni+Nj),其中Nij為材料i和j共有的擴(kuò)增片段總數(shù),Ni為材料i中出現(xiàn)的擴(kuò)增片段數(shù),Nj為材料j中出現(xiàn)的擴(kuò)增片段數(shù)。以Clustering程序中SHAN進(jìn)行UPGMA(非加權(quán)組平均法)聚類分析,并通過Treeplot模塊生成聚類圖。
將數(shù)據(jù)轉(zhuǎn)換成Structure默認(rèn)的數(shù)據(jù)格式,并通過Structure軟件進(jìn)行群體遺傳結(jié)構(gòu)分析。將K值設(shè)為2 —20,采用馬爾可夫鏈的蒙特卡洛模擬算法(markov chain monte carlo,MCMC),不作數(shù)迭代(length of burn-in period)設(shè)為10 000次,再將不作數(shù)迭代后的MCMC設(shè)為100 000次。但依此得到的數(shù)據(jù)所繪制的折線圖常常不能提供真正的 K值。因此,在此基礎(chǔ)上推算對數(shù)變化率ΔK來更為準(zhǔn)確的反應(yīng)真正的K值[32]。ΔK的計(jì)算公式為:ΔK=m(|L(K+1)-2L(K)+L(K-1)|)/s[L(K)]。L(K)為每個(gè)K對應(yīng)的對數(shù)值,s為標(biāo)準(zhǔn)差,m為平均值。根據(jù)ΔK的變化規(guī)律來確定最適的群體數(shù)目,構(gòu)建遺傳結(jié)構(gòu)圖。計(jì)算群體中品種基因組變異源于該群體中的概率Q,用于分析其遺傳成分[33]。
2.1高效率 SSR引物的篩選與多態(tài)性位點(diǎn)百分率 P的計(jì)算
利用供試材料中30份棗品種的基因組DNA為模板,從課題組前期設(shè)計(jì)并篩選出的SSR引物[28]中進(jìn)行二次引物篩選。根據(jù)擴(kuò)增效果,從中選取23對多態(tài)性和重復(fù)性好的SSR引物(表2,圖1),用于255份棗種質(zhì)的SSR分析。
23對引物在255份供試棗種質(zhì)中共擴(kuò)增出117條多態(tài)性條帶,多態(tài)位點(diǎn)百分率達(dá) 100%。各引物擴(kuò)增的多態(tài)性條帶數(shù)為2—10條,平均每對引物擴(kuò)增5.09個(gè)多態(tài)性條帶,擴(kuò)增片段范圍90—290 bp(圖2)。BOTSTEIN等[31]提出了衡量基因變異程度高低的多態(tài)性信息量指標(biāo)PIC;PIC>0.5時(shí),該引物為高度多態(tài)性信息引物;0.25<PIC<0.5,為中度多態(tài)性信息引物;PIC<0.25,為低度多態(tài)性信息引物。本研究中篩選出的引物 PIC值變幅為 0.359—0.727(平均值0.548),均為高度或重度多態(tài)性信息引物(表2)。
表1 供試品種材料Table 1 Cultivars used in the study
編號Code名稱Cultivar原產(chǎn)地Origin編號Code編號Code名稱Cultivar原產(chǎn)地Origin名稱Cultivar原產(chǎn)地Origin 76 新鄭長雞心棗(D)Xinzhengchangjixinzao河南He’nan 102 喀什葛爾小棗(B)Kashigeerxiaozao山西Shanxi 128 朝陽齊脆棗(F)Chaoyangqicuizao遼寧Liaoning 77 南京棗(P)Nanjingzao浙江Zhejiang 103 吾庫扎克小棗(B)Wukuzhakexiaozao山西Shanxi 129 朝陽棉套棗(D)Chaoyangmiantaozao遼寧Liaoning 78 保定斑棗(F)Baidingbanzao河北Hebei 104 新疆小圓棗(D)Xinjiangxiaoyuanzao山東Shandong 130 鮑莊大鈴棗(D)Baozhuangdalingzao山東Shandong 79 合陽鈴鈴棗(F)Heyanglinglingzao陜西Shannxi 105 泰安靈棗(D)Tai’anlingzao河南He’nan 131 鮑莊小棗(B)Baozhuangxiaozao山東Shandong 80 延川狗頭棗(B)Yanchuangoutouzao陜西Shannxi 106 泰安疙瘩棗(F)Tai’angedazao山東Shandong 132 鮑莊小圓棗(B)Baozhuangxiaoyuanzao山東Shandong 81 雞心棗(D)Jixinzao河南He’nan 107 泰安大脆棗(F)Tai’andacuizao湖南Hu’nan 133 北京31(U)Beijing 31北京Beijing 82 北京纓絡(luò)棗(B)Beijingyingluozao北京Beijing 108 河津晉棗(F)Hejinjinzao湖南Hu’nan 134 鮑莊尖棗(U)Baozhuangjianzao山東Shandong 83 武鄉(xiāng)碳棗(D)Wuxiangyazao山西Shanxi 109 萬榮脆棗(B)Wanrongcuizao湖南Hu’nan 135 朝陽無核棗(F)Chaoyangwuhezao遼寧Liaoning 84 武鄉(xiāng)甜棗(D)Wuxiangtianzao山西Shanxi 110 萬榮耬疙瘩(D)Wanronglougeda湖南Hu’nan 136 北京大脆棗(F)Beijingdacuizao北京Beijing 85 太原十月紅(D)Taiyuanshiyuehong山西Shanxi 111 臨猗圓鈴棗(D)Linyiyuanlingzao湖南Hu’nan 137 太谷郎棗(B)Taigulangzao山西Shanxi 86 阜陽螞蟻棗(B)Fuyangmayizao安徽Anhui 112 定襄小棗(B)Dingxiangxiaozao山西Shanxi 138 太谷壺瓶酸(F)Taiguhupingsuan山西Shanxi 87 西雙版納小棗(D)Xishuangbannaxiaozao云南Yunnan 113 寧陽宣鈴棗(F,P)Ningyangxuanlingzao新疆Xinjiang 139 榆次面棗(U)Yucimianzao山西Shanxi 88 昆明棗(U)Kunmingzao云南Yunnan 114 鎮(zhèn)平九月寨(D)Zhenpingjiuyuezhai新疆Xinjiang 140 榆次奶頭棗(F)Yucinaitouzao山西Shanxi 89 云南2號(U)Yunnan 2云南Yunnan 115 成武冬棗(F)Chengwudongzao新疆Xinjiang 141 臨猗珍珠棗(U)Linyizhenzhuzao山西Shanxi 90 山西哈八棗(D)Shanxihabazao山西Shanxi 116 溆浦小果算盤棗(F)Xupuxiaoguosuanpan山東Shandong 142 榆次長木棗(D)Yucichangmuzao山西Shanxi 91 永濟(jì)雞蛋棗(F)Yongjijidanzao山西Shanxi 117 溆浦巖棗(D)Xupuyanzao山東Shandong 143 太谷沒心紅(B)Taigumeixinhong山西Shanxi 92 山西小令棗(U)Shanxixiaolingzao山西Shanxi 118 溆浦香棗(D)Xupuxiangzao山東Shandong 144 大饃棗(U)Damozao山西Shanxi 93 湖北鈴鐺棗(U)Hubeilingdangzao湖北Hubei 119 溆浦木棗(D)Xupumuzao山西Shanxi 145 交城牙棗(D)Jiaochengyazao山西Shanxi 94 河北圓棗(B)Hebeiyuanzao河北Hebei 120 溆浦米棗(F)Xupumizao山西Shanxi 146 太谷沒心核(U)Taigumeixinhe山西Shanxi 95 湖北雞心棗(U)Hubeijixinzao湖北Hubei 121 臨猗甜酸棗(F)Linyitiansuanzao山西Shanxi 147 晉棗1號(B)Jinzao 1山西Shanxi 96 西安羊奶棗(F)Xi’anyangnaizao陜西Shannxi 122 臨猗脖脖棗(D)Linyibobozao山西Shanxi 148 新蔡大圓豐棗(U)Xincaidayuanfengzao河南He’nan 97 大荔林檎棗(B)Dalilinqinzao陜西Shannxi 123 河津木棗(D)Hejinmuzao山西Shanxi 149 駐馬店羊角棗(F)Zhumadianyangjiaozao河南He’nan 98 佳縣細(xì)腰腰棗(D)Jiaxianxiyaoyaozao陜西Shannxi 124 北京馬牙棗(F)Beijingmayazao北京Beijing 150 保定月光(F)Baodingyueguang河北Hebei 99 溆浦薄皮棗(F)Xupubopizao湖南Hu’nan 125 泰安金絲(B)Tai’anjinsi山東Shandong 151 運(yùn)城蛤蟆棗(F)Yunchenghamazao山西Shanxi 100 猴頭棗(B)Houtouzao山東Shandong 126 山東梨棗(F)Shandonglizao山東Shandong 152 運(yùn)城脆棗(F)Yunchengcuizao山西Shanxi 101 滕州落地紅(D)Tengzhouluodihong山東Shandong 127 慶云小梨棗(F)Qingyunxiaolizao山東Shandong 153 榆次晚紅棗(U)Yuciwanhongzao山西Shanxi
?
F:鮮食 Fresh;D:制干 Dry;B:兼用 Fresh and dry;P:加工 Processing;O:觀賞 Ornamental;U:不詳 Unknown
圖1 篩選出的引物(JSSR97、JSSR128)對30份棗材料的擴(kuò)增結(jié)果Fig.1 Amplified results of 30 jujube cultivars with selected primer pairs JSSR97 and JSSR128
圖2 引物JSSR183對255份棗材料的擴(kuò)增結(jié)果Fig.2 Amplified results of 255 jujube cultivars with primer JSSR183
表2 篩選出的23對多態(tài)性SSR引物Table 2 The 23 SSR primer pairs selected for this study
2.2部分棗品種特有SSR標(biāo)記的挖掘
供試棗品種的SSR分析結(jié)果以Excel表格形式保存,不同品種的SSR指紋以SSR引物名稱為前綴、以該標(biāo)記(擴(kuò)增帶)的分子量為后綴,得到每個(gè)品種在某個(gè)標(biāo)記的帶型編號。在255個(gè)供試品種中,有40個(gè)棗品種只需1—2個(gè)特有的SSR標(biāo)記即可鑒別出來(表3)。從表1和表3可以看出,很多同一區(qū)域來源的棗品種(如同樣來源于陜西省關(guān)中平原東北部蒲城縣的‘蒲城直社疙瘩棗’‘蒲城直社疙瘩棗’和‘蒲城晉棗’可以被1—2個(gè)特有SSR標(biāo)記區(qū)分開,這為地方品種的準(zhǔn)確鑒定和資源管理提供了有效手段。
表3 40個(gè)棗品種的特有SSR指紋Table 3 Special SSR fingerprints of 40 jujube cultivars
2.3供試棗品種的聚類分析
利用23對引物擴(kuò)增出的117條多態(tài)性條帶,可將供試255個(gè)品種的251個(gè)品種分開,占98.43%,依據(jù)23對SSR引物擴(kuò)增位點(diǎn)構(gòu)建的0-1矩陣,計(jì)算出供試材料間的配對遺傳相似系數(shù)(GS),其變化范圍為0.71 —1.00。由聚類圖(圖3)可看出,在聚類閥值為0.71處,北京花生棗單獨(dú)聚到一類,說明其與其他棗品種親緣關(guān)系較遠(yuǎn),分析原因可能是北京花生棗是獨(dú)立起源的品種,也可能是其在長期栽培中與其他棗品種基因交流較少所致;其余254個(gè)品種分為14個(gè)亞類,包括4個(gè)大亞類(每類24—56個(gè)品種)和10個(gè)小亞類(1—10個(gè)品種)。在10個(gè)小亞類中,湖南的‘溆浦巖棗’和陜西的‘合陽鈴鈴棗’亦均單獨(dú)為一個(gè)小類;同時(shí)有少部分品種沒有分開,如‘奉節(jié)雞蛋棗’和‘溆浦雞蛋棗’、‘陜西奶棗’和‘天津大馬牙棗’之間的相似系數(shù)為1.00,表明‘奉節(jié)雞蛋棗’和‘溆浦雞蛋棗’、‘陜西奶棗’和‘天津大馬牙棗’的親緣關(guān)系很近。‘奉節(jié)雞蛋棗’和‘溆浦雞蛋棗’分別來自重慶、湖南,這兩個(gè)品種棗果的果形都是近圓形;‘陜西奶棗’和‘天津大馬牙棗’分別來自陜西和天津,果形均較尖,本試驗(yàn)中檢測出的兩兩品種間較近的親緣關(guān)系也可能是不同地區(qū)間栽培引種造成的,也可能是兩兩品種是同物異名,或者是本研究中所用引物數(shù)量較少,尚不能將這些近緣品種完全分開。
從聚類圖中還可以看出:(1)一些類群中,棗品種間的遺傳關(guān)系與其原產(chǎn)地有明顯的相關(guān)性。如I和II組的棗品種基本都是來自山西,II組的棗品種基本都來自北京,而O組的基本來自湖南;來自陜西的‘大荔鈴鈴棗’‘大荔蜂蜜罐’和‘大荔疙瘩棗’聚在一起,來自山東的‘泰安大脆棗’‘酥脆棗’和‘泰安疙瘩棗’也都聚在一起。(2)另一些類群中(如C、E、K組),棗品種來自于不同的產(chǎn)地,遺傳關(guān)系與地理分布似乎沒有必然的聯(lián)系。這些類群相對比較分散,每一小類群中品種數(shù)量不多。如Ⅳ類群中7個(gè)棗品種來自于6個(gè)不同地區(qū);Ⅴ類群中20個(gè)品種主要來自河北、山西和山東;Ⅵ類群中品種主要來自江蘇和湖南。(3)結(jié)合聚類圖和供試品種的用途和原產(chǎn)地分析,不同棗品種間的親緣關(guān)系與品種原產(chǎn)地有一定相關(guān)性,但和品種用途沒有顯著相關(guān)性,例如第一大類中就包括了制干、鮮食、加工等不同用途的品種。
2.4供試棗種質(zhì)的遺傳結(jié)構(gòu)分析
基于上述獲得的SSR分析數(shù)據(jù),利用STRUCTURE軟件分析供試棗群體的遺傳結(jié)構(gòu),繪制K與ΔK的關(guān)系圖(圖4),K=15時(shí),ΔK最大。據(jù)此,將255個(gè)棗品種分成15個(gè)群組,進(jìn)一步以K=15繪制了基于數(shù)學(xué)模型模擬的255個(gè)棗品種遺傳結(jié)構(gòu)的貝葉斯分配圖(圖5)。并計(jì)算出了15個(gè)居群中最大Q值分布(表4)。
表4 各群體Q值分布Table 4 Distribution of Q-value of fifteen groups
圖3 基于SSR分析的255個(gè)棗品種聚類圖Fig.3 Dendrogram of 255 jujube cultivars based on SSR markers
圖4 棗255個(gè)品種的K值與ΔK的關(guān)系Fig.4 Graphical relationship between K and ΔK for 255 jujube cultivars
圖5 255個(gè)棗品種的遺傳結(jié)構(gòu)分析Fig.5 Population structure of 255 jujube cultivars
圖5中不同的色塊代表不同的群體,縱坐標(biāo)表示各居群中的品種占某居群祖先成分的比例,橫坐標(biāo)為樣品編號。從圖5中可看出,根據(jù)各個(gè)品種的混合比率,將255份供試材料分成15個(gè)居群,進(jìn)一步分析表明,一些居群(如3、8、9、12、14居群)遺傳背景比較一致,絕大部分來源于相同的栽培區(qū)域,混雜程度相對較低;而有的居群(如2、4、5、13居群)分配率較高,群體間混合程度相對較高,來源于不同的栽培區(qū)域,群體間的遺傳物質(zhì)交流相對較多。從遺傳結(jié)構(gòu)分析也發(fā)現(xiàn),不同群體的品種和其用途沒有顯著相關(guān)性,但與聚類分析(圖3)的結(jié)果相似。
Structure群體遺傳結(jié)構(gòu)分析中,當(dāng)某一材料在某類群中的Q≥0.6時(shí),則認(rèn)為該材料血緣關(guān)系相對比較單一,否則認(rèn)為該材料血緣關(guān)系來源復(fù)雜[33]。從根據(jù)供試材料在各個(gè)群體中的Q值分布(表4),255個(gè)供試材料中有36個(gè)品種Q值小于0.6,占所有供試材料總數(shù)的14.1%,Q值大于0.8和0.9的品種分別占68.2%和56.5%,說明各群體中大部分品種血緣關(guān)系比較單一,較少品種含有其他類群的遺傳成分。整體看,來自棗主栽區(qū)域山西(居群 6、10、11)、陜西(居群14)和河北(居群1)的品種形成了以當(dāng)?shù)仄贩N為主的居群,說明這些地區(qū)在長期的栽培演化過程中選育出了豐富的棗品種資源,其中來自山西或陜西的棗品種出現(xiàn)在絕大部分居群中,說明這兩個(gè)省的資源在不同群體間的基因交流中發(fā)揮了重要作用;南方區(qū)域只有來自湖南的棗品種形成了相對獨(dú)自的居群,可能是其起源相對單一,且在較長一段時(shí)間的栽培過程中,栽培環(huán)境比較封閉,近親繁殖,和其他產(chǎn)地棗品種間基因交流較少所致(居群8)。
本研究選用23對SSR引物對255個(gè)棗品種進(jìn)行了分析,共擴(kuò)增出117條多態(tài)性譜帶,多態(tài)位點(diǎn)比率達(dá)到100%。在棗樹上,麻麗穎等[8]報(bào)道的SSR標(biāo)記多態(tài)性比率也為 100%,而李莉等[34]報(bào)道的RAPD標(biāo)記多態(tài)性為 99.78%,白瑞霞[35]用 AFLP標(biāo)記的多態(tài)性則僅為 64.30%,謝永波[36]用 AFLP標(biāo)記的多態(tài)性為78.7%,說明本研究的SSR標(biāo)記的多態(tài)性效率較高。分析原因一方面是因?yàn)楸狙芯恐兴靡锝?jīng)過了二次篩選,另一方面也是因?yàn)楣┰嚥牧隙唷⑦z傳多樣性豐富而使得多態(tài)位點(diǎn)比率較高。同時(shí),本試驗(yàn)也注意到,不同 SSR引物對棗品種的鑒別能力有較大差異,并不是所有引物的多態(tài)性都較高,進(jìn)一步說明篩選高效率引物的必要性。
中國棗品種繁多,不同品種間復(fù)雜的遺傳關(guān)系一直是研究熱點(diǎn)。本研究利用 SSR技術(shù)進(jìn)行了 22個(gè)省區(qū)主產(chǎn)地 255個(gè)棗品種的遺傳多樣性和群體結(jié)構(gòu)分析,提供了大量的多態(tài)性數(shù)據(jù)信息,為將來表型數(shù)據(jù)和基因數(shù)據(jù)的關(guān)聯(lián)性分析奠定了良好的基礎(chǔ)。聚類和群體結(jié)構(gòu)兩種分析結(jié)果均表明,在棗品種的群體結(jié)構(gòu)中大部分品種與來源區(qū)域有一定的相關(guān)性。相關(guān)性不明顯的棗品種可能是區(qū)域間品種經(jīng)過頻繁的基因交流或重組培育而成,從而融合了不同區(qū)域品種的特點(diǎn),沒有了明顯的區(qū)域特征。前人利用SSR[17]、ISSR[18]、AFLP[2]進(jìn)行的研究也表明,遺傳多樣性在一定程度上能夠反映品種的地理分布特點(diǎn)。李海濤[26]對河南主栽棗品種的 ISSR分析表明,棗的遺傳變異主要來自于居群內(nèi)的變異,來自于居群間的變異貢獻(xiàn)率較低。殷曉[27]對黃河沿岸六省48個(gè)棗品種進(jìn)行的遺傳多樣性研究表明,地理區(qū)域內(nèi)變異(93%)遠(yuǎn)大于地理區(qū)域間分化(7%)。本研究中,255個(gè)供試材料中Q值小于0.6的品種36個(gè),僅占14.1%(表4),也進(jìn)一步說明大部分品種血緣關(guān)系比較單一,以居群內(nèi)或地理區(qū)域內(nèi)變異為主。這些結(jié)果均表明,現(xiàn)有的棗種質(zhì)資源可能是不同區(qū)域起源的,在物種演化過程中區(qū)域內(nèi)品種間進(jìn)行了頻繁的基因交流和重組,進(jìn)而產(chǎn)生了更為豐富的資源結(jié)構(gòu)組成。
利用23對SSR引物在255個(gè)供試品種中共檢測出117個(gè)多態(tài)性位點(diǎn),平均每對引物擴(kuò)增多態(tài)位點(diǎn)數(shù)為5.09,PIC值變幅為0.359—0.727,平均為0.548;為其中40個(gè)棗品種找到了1—2個(gè)各自特有的SSR標(biāo)記;255個(gè)棗品種的群體遺傳結(jié)構(gòu)與聚類分析結(jié)果基本一致,不同地理環(huán)境在棗品種的群體進(jìn)化中發(fā)揮了較重要的作用,但不同棗品種的遺傳關(guān)系與品種用途沒有顯著相關(guān)性。
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(責(zé)任編輯 趙伶俐)
Genetic Diversity and Structure of 255 Cultivars of Ziziphus jujuba Mill.
LIU Xiu-yun1,LI Hui1,2,LIU Zhi-guo1,ZHAO Jin3,LIU Meng-jun1,4
(1Reserch Center of Chinese Jujube,Agricultural University of Hebei,Baoding 071001,Hebei;2Germplasm Resources Institute of Ningxia Academy of Agriculture and Forestry Sciences,Yinchuan 750002;3College of Life Science,Agricultural University of Hebei,Baoding 071001,Hebei;4Beijing Collaborative Innovation Center for Eco-Enviromental Improvement with Forestry and Fruit Trees,Beijing 102206)
【Objective】 There are abundant jujube germplasm resources in China. A total of 255 cultivars of Ziziphus jujuba Mill. from 22 provenances were used as materials to reveal their genetic diversity and phylogenetic relationship by SSR analysis,and the results of analysis would help us to manage jujube germplasm resources and offer references for molecular maker-assisted breeding. 【Method】 Good genomic DNA was extracted from young leaves of jujube germplasm resources following the improved CTAB method,and then were amplified by simple sequence repeat molecular markers to analyze genetic diversity and genetic structure with the selected high-efficiency primer pairs which were excavated based on the genome sequencing. Separation of the amplified fragments was performed on 8% denaturing polyacrylamide gels and the gels were stained with AgNO3for visualizing the SSR fragments. The data were counted by presence or absence of the band and the percentage of polymorphic loci (PIC) was calculated. UPGMA cluster analysis was carried by software NTSYS,the optimal number of groups and population genetic structure was analyzed by software Structure.【Result】Totally,117 polymorphic alleles were revealed with 23 primer pairs which was selected from 64 primer pairs,each primer amplified polymorphic loci ranged from 2 to 10,with an average of 5.09 for each primer pairs. Polymorphism information content (PIC) values for the primer pairs ranged from 0.359 to 0.727,with an average of 0.548,these polymorphisms primers could be further applied to other study. The fingerprint for some jujube cultivars was established with 1-2 markers,providing a reference for the management of jujube germplasm. Meanwhile,based on the UPGMA cluster analysis,255 cultivars were divided into fifteen subgroups,which included four big groups and eleven small groups. Similarity coefficients among the cultivars were between 0.71 to 1.00,‘Beijinghuashengzao’ was clustered into one separate group,which has a distant relationship with other cultivars. The similarity coefficients of ‘Fengjiejidanzao’ and ‘Xupujidanzao’,‘Shannxinaizao’ and ‘Tianjindamayazao’ were both 1.00. In some subgroups the genetic relationship between cultivars and their provenances has a significant positive correlation,but the cultivars and their uses has no significant correlation. Based on K and ΔK values,255 jujube cultivars were also divided into fifteen populations by the population genetic structure analysis. The kinship among cultivars in the same population was relatively simple,and a few cultivars contained genetic component of other groups. The cultivars from Shanxi or Shannxi were distributed in most populations,indicating jujube cultivars of the two provinces played important roles in the gene exchange among populations. The jujube cultivars from Hunan of the South region formed a relatively alone population,indicating that the cultivars might be from the same source,or in the long-term cultivation few times of gene exchange were happened in Hunan cultivars with other populations. Different geographical environment played a key role in the evolution of jujube germplasm populations,some cultivars were selected from the same geographical environment and the others were selected by genetic recombination among those cultivars from the various geographical environment. Meanwhile,the consistency of the two different methods was further verifed the accuracy of the results,which provide useful clues and reference for the genetic diversity and structure of jujube germplasm.【Conclusion】Geographical environment play significant roles in the population evolution of jujube cultivars,affecting the genetic structure composition between different habitats.
Chinses jujube; SSR markers; provenances; genetic diversity; population structure
2016-01-18;接受日期:2016-04-13
“十二五”國家科技支撐計(jì)劃(2013BAD14B03)、北京市2011協(xié)同創(chuàng)新中心項(xiàng)目(PXM2016_014207_000038)、河北農(nóng)業(yè)大學(xué)青年學(xué)術(shù)帶頭人項(xiàng)目
聯(lián)系方式:劉秀云,E-mail:jingxianyu705@126.com。李慧,E-mail:1063979927@qq.com。劉秀云和李慧為同等貢獻(xiàn)作者。通信作者劉孟軍,E-mail:lmj1234567@aliyun.com。通信作者趙錦,E-mail:zhaojinbd@126.com