山东石榴种质资源遗传多样性分析与DNA指纹图谱构建

吴志苹1,杨 阳1,罗 华2,马 丽1*

1枣庄学院生命科学学院,山东枣庄 277160; 2枣庄市石榴研究中心,山东枣庄 277300)

摘 要:【目的】探究山东石榴种质资源的遗传多样性并构建DNA指纹图谱,为科学分类、品种鉴定及遗传改良提供理论依据。【方法】以76份石榴种质资源为材料,用16个ISSR引物进行PCR扩增,采用UPGMA法构建聚类图,利用Pop-Gene软件分析遗传多样性,分析引物的区分效率并构建DNA指纹图谱。【结果】16个引物共扩增305个位点,其中多态性比率为88.2%;平均等位基因数()为1.980 7,有效等位基因数(Ne)为1.651 7,Nei’s基因多样性(He)为0.370 4,Shannon信息指数(I)为0.545 1,表明山东石榴遗传多样性较丰富;聚类结果将76份种质聚为4类;利用引物组合UBC834/UBC835成功构建了76份种质的DNA指纹图谱。【结论】本研究构建的DNA指纹图谱具有品种特异性,可为石榴种质的分类、鉴定及新品种选育提供科学依据。

关键词:石榴;ISSR分子标记;遗传多样性;DNA指纹图谱

石榴(Punicɑ grɑnɑtum L.)为千屈菜科(Lythraceae)石榴属(Punicɑ L.)落叶灌木或小乔木[1],是世界上重要的经济林树种之一。果实富含维生素C等多种营养成分,具有抗氧化、抗炎、抗癌和预防心血管疾病等重要功能[2]。石榴在中国栽培历史悠久,2023年全国的栽培面积11万hm2,年产量200万t[3]。山东省是全国石榴主产区之一,目前栽培面积达1万hm2,年产量10万t,石榴种植是农民增收致富的重要产业[4]。石榴为异花授粉果树,由于栽培过程中自发突变、不同地域间的引种、品种交换等造成亲缘关系模糊,谱系混乱现象突显,严重影响了种质资源的高效利用。传统上对石榴种质间的遗传关系、品种鉴定经常依据花色、瓣型、果色等表型性状,但这些性状极易受环境影响,导致结果不准确。市场上“假树苗”以次充好现象层出不穷,造成新品种权得不到保护,极大地影响了育种单位的积极性和果农的经济利益。随着商业化育种进程加速,石榴种质资源同质化现象加剧,传统形态学鉴定方法难以满足精准分类需求,分子标记技术的发展为解决这类问题提供了新途径。

采用DNA标记技术鉴定石榴种质能从分子水平解析种质间的遗传差异,比形态学、细胞学更准确[5-7]。目前,多种分子标记已应用于研究石榴种质资源的遗传关系分析,其中RAPD标记使用最广泛但不稳定。因此,AFLP、SSR等分子标记更多地应用于石榴属植物间的遗传关系研究[8]。基于SSR技术建立的ISSR分子标记无需预知物种基因组信息,多态性高、重复性好、成本较低,在植物遗传多样性、品种鉴定、遗传图谱构建等研究中应用广泛,目前已用于樱桃[9]、枇杷[10]、番石榴[11]、桃[12]、匙羹藤[13]等植物种质资源的研究。然而,目前大多数研究多聚焦于局部种质资源,缺乏系统性分析。本研究采用ISSR技术,系统分析山东产区石榴种质资源的遗传多样性、亲缘关系并构建指纹图谱数据库,为石榴的科学分类、品种鉴定和遗传改良提供理论基础和科学依据,对今后优异种质的挖掘及高效利用具有重要意义。

1 材料和方法

1.1 材料来源

供试76份山东石榴种质资源均来自中国石榴种质资源圃(位于山东省枣庄市),石榴种质资源信息见表1。

表1 76份石榴种质资源信息
Table 1 Information on 76 pomegranate germplasm accessions

编号Code名称Name花色Flower color瓣型Petal shape果色Pericarp color籽粒性状Seed character 1 2 3 4 5 6峄城实生石榴Yicheng Seedling Pomegranate峄城青皮月季Yicheng Cyan-skinned Rose峄城重瓣粉红月季Yicheng Double Petal Pink Rose峄城大果红皮月季Yicheng Large-fruit Red-skinned Rose峄城小叶2号Yicheng Small-leaf No.2峄城小叶3号Yicheng Small-leaf No.3红单红硬Red红Red粉红Pink红Red红Red红Red Single petal单Single petal重Double petal单Single petal单Single petal单Single petal Red青Cyan青Cyan红Red红Red红Red Hard硬Hard硬Hard硬Hard硬Hard硬Hard

表1(续) Table 1 (Continued)

编号Code名称Name花色Flower color瓣型Petal shape果色Pericarp color籽粒性状Seed character 7 8 9白单白硬10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34峄城小籽三白Yicheng Small-seed Sanbai峄城大个红皮Yicheng Big Pomegranate Red-skinned峄城小叶红皮Yicheng Small-leaf Red-skinned峄城大叶Yicheng Large-leaf峄城红籽白石榴Yicheng Red-seed White Pomegranate峄城红皮月季Yicheng Red-skinned Rose峄城发芽红Yicheng Sprouting Red峄城白皮酸Yicheng White-skinned Sour峄城单瓣粉红白皮酸Yicheng Single Petal Pink White-skinned Sour峄城单瓣玛瑙Yicheng Single Petal Agate峄城红牡丹石榴Yicheng Red Peony Pomegranate峄城重瓣白皮酸Yicheng Double Petal White-skinned Sour峄城小红牡丹Yicheng Small Red Peony峄城抗寒砧木1号Yicheng Cold-resistant Rootstock No.1峄城竹叶青Yicheng Bamboo-leaf Cyan峄城重瓣白花酸Yicheng Double Petal White Flower Sour峄城超红Yicheng Ultra Red峄城青皮大籽Yicheng Cyan-skinned Large-seed峄城白楼无刺Yicheng Bailou Thornless峄城和顺庄无刺Yicheng Heshunzhuang Thornless峄城紫粒青皮甜Yicheng Purple-seed Cyan-skinned Sweet峄城超青Yicheng Ultra Cyan峄城超大白皮甜Yicheng Extra-large White-skinned Sweet峄红1号Yihong No.1峄城重瓣红皮酸Yicheng Double Petal Red-skinned Sour峄城大粒青皮岗榴Yicheng Large-seed Cyan-skinned Gangliu峄城峄青Yicheng Yiqing峄城单瓣粉红酸Yicheng Single Petal Pink Sour White红Red红Red红Red白White红Red红Red白White粉红Pink复色Multiple红Red白White红Red红Red红Red白White红Red红Red红Red红Red红Red红Red白White红Red红Red红Red红Red粉红Pink Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal复Multiple petal复Multiple petal重Double petal重Double petal单Single petal复Multiple petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal重Double petal单Single petal单Single petal单Single petal White红Red红Red红Red白White红Red红Red白White白White乳白Milky white红Red白White红Red红Red青Cyan白White红Red青Cyan青Cyan青Cyan青Cyan青Cyan白White红Red红Red青Cyan青Cyan青Cyan Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard

表1(续) Table 1 (Continued)

编号Code名称Name花色Flower color瓣型Petal shape果色Pericarp color籽粒性状Seed character 35红重紫硬36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62峄城红花重瓣紫皮酸Yicheng Red Flower Double Petal Purple-skinned Sour峄城青皮大籽Yicheng Cyan-skinned Large-seed峄城红花重瓣青皮酸Yicheng Red-flower Double Petal Cyan-skinned Sour峄城粉红重瓣白皮甜Yicheng Pink Double Petal White-skinned Sweet峄城青皮谢花甜Yicheng Cyan-skinned Xiehuatian峄城半口青皮谢花甜Yicheng Bankou Cyan-skinned Xiehuatian峄城大红皮甜Yicheng Large Red-skinned Sweet峄城白皮大籽Yicheng White-skinned Large-seed峄城胭脂红Yicheng Rouge Red峄城超大青皮甜Yicheng Extra-large Cyan-skinned Sweet峄城白皮马牙甜Yicheng White-skinned Mayatian峄城败育石榴Yicheng Abortion Pomegranate峄城玛瑙石榴Yicheng Agate Pomegranate峄城半口青皮酸Yicheng Half Cyan-skinned Sour峄城红皮马牙甜Yicheng Red-skinned Mayatian峄城多刺Yicheng Thorny峄城青厚皮Yicheng Thick Cyan-skinned峄城大红皮酸Yicheng Large Red-skinned Sour峄城大青皮酸Yicheng Large Cyan-skinned Sour峄城厚皮甜Yicheng Thick-skinned Sweet宁津单瓣玛瑙Ningjin Single Petal Agate宁津红皮酸Ningjin Red-skinned Sour泰山红牡丹Taishan Red Peony白珍珠White Pearl潍坊青皮Weifang Cyan-Skinned蒙阳红直立Mengyang Red Upright墨石榴Ink Pomegranate月季石榴Rose Pomegranate Red红Red红Red粉红Pink红Red红Red红Red白White红Red红Red白White红Red复色Multiple红Red红Red红Red红Red红Red红Red红Red复色Multiple红Red红Red白White红Red红Red红Red红Red Double petal单Single petal重Double petal重Double petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal重Double petal单Single petal单Single petal单Single petal单Single petal单Single petal Purple青Cyan青Cyan白White青Cyan青Cyan红Red白White红Red青Cyan白White青Cyan青Cyan青Cyan红Red青Cyan青Cyan红Red青Cyan青Cyan青Cyan红Red红Red白White青Cyan红Red紫Purple青Cyan Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard

表1(续) Table 1 (Continued)

编号Code名称Name花色Flower color瓣型Petal shape果色Pericarp color籽粒性状Seed character 63红单红硬64 65 66 67 68 69 70 71 72 73 74 75 76苍山红皮Cangshan Red-skinned山东大叶红皮Shandong Large-leaf Red-skinned鲁白榴2号Lubailiu No.2鲁青榴3号Luqingliu No.3白花单瓣酸White Flower Single Petal Sour青皮马牙酸Cyan-skinned Maya Sour大马牙Damaya岗榴Gangliu秋艳Qiuyan黄金榴Golden Pomegranate日本看石榴Japanese Ornamental Pomegranate候孟青皮甜Houmeng Cyan-skinned Sweet绣球牡丹Hydrangea Peony紫皮甜Purple-Skinned Sweet Red红Red白White红Red白White红Red红Red红Red红Red白White红Red红Red红Red红Red Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal单Single petal重Double petal单Single petal复Multiple petal单Single petal Red红Red白White青Cyan青Cyan青Cyan青Cyan青Cyan青Cyan黄Yellow红Red青Cyan青Cyan紫Purple Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard硬Hard

1.2 DNA提取及ISSR-PCR扩增检测

石榴嫩叶基因组DNA提取、ISSR-PCR扩增条件及检测参考朱薇等[14]的方法。

1.3 数据分析

以DL2000 DNA Marker(天根生化科技有限公司,北京)的谱带分子质量为参考标准,用Quantity One软件结合肉眼观察获得扩增DNA谱带分子质量,根据谱带在凝胶同一迁移率位置上的有无,按照有扩增谱带记为“1”,无扩增谱带记为“0”的统计标准,形成每条引物标记的(0,1)数据原始矩阵。统计并计算引物多态性百分比率。引物多态性比率=a/(a+b)×100%,a为多态条带数目,b为所有品种共享数目。用PopGene软件统计遗传多样性参数。用NTSYS2.10软件计算遗传相似系数(GS),用UPGMA法绘制遗传关系图。通过聚类分析单引物或引物组合对供试品种的区分效率,品种区分率高的引物用于构建DNA指纹。

2 结果与分析

2.1 ISSR引物扩增结果分析

部分ISSR引物扩增PAGE电泳图如图1所示,供试品种扩增谱带清晰,产生的位点迁移率各异,多态性较好。由表2可知,16个引物所得位点数为14~25个,每条引物平均产生位点19个,多态性位点16.8个,引物多态性比率为70.6%~95.4%。引物UBC834扩增出来的位点最多,多态性比率较好,为92.0%。引物UBC827的多态性位点比率最高,为95.4%。引物平均多态性比率为88.2%,说明这16个引物适合山东石榴种质资源遗传多样性研究。

图1 引物UBC835对部分石榴种质的扩增结果
Fig. 1 Amplification results of primer UBC835 for some pomegranate germplasm accessions

表2 ISSR引物信息、扩增结果及品种区分效率
Table 2 ISSR primers information, amplification results and cluster discrimination rate

引物名称Primer name UBC834 UBC808 UBC809 UBC841 UBC890 UBC811 UBC842 UBC816 UBC835 UBC827 UBC861 UBC880 UBC840 UBC826 UBC888 UBC810总计Total平均Average引物序列 (5′ to 3′)Primer sequence(5′ to 3′)(AG)8YT(AG)8C(AG)8G(GA)8YC HVH(TG)7(GA)8C(GA)8YG(CA)8T(AG)8YC(AC)8G(ACC)6(GGAGA)3(GA)8YT(AC)8C BDB(CA)7(GA)8T退火温度Ta/℃55 52 52 52 52 50 52 50 52 50 50 50 50 52 52 52谱带数Number of bands 25 17 22 24 15 14 23 17 23 22 15 18 20 17 16 17 305 19多态性谱带数Number of polymorphic bands 23 16 20 20 13 12 19 16 20 21 14 15 18 12 15 15 269 16.8多态性比率Percentage of polymorphic bands, PPB/%92.0 94.1 90.9 83.3 86.7 85.7 82.6 94.1 86.9 95.4 93.3 83.3 90.0 70.6 93.7 88.2-88.2聚类区分率Cluster discrimination rate/%77.63 19.70 31.58 76.32 34.21 34.21 68.42 36.84 85.53 72.37 34.21 10.53 32.89 30.26 15.78 31.58

2.2 单引物的区分效率

统计每个引物对76份种质的区分效率,结果如表2所示:单引物的区分效率为10.53%~85.53%;引物UBC835的区分率最高,为85.53%,但仍有11份种质不能区分开。因此,单引物对76份种质的区分能力较差,需要筛选种质区分率较高的引物组合构建DNA指纹图谱。

2.3 核心引物组合的区分效率

将区分效率较高的引物UBC827、UBC834、UBC835、UBC841和UBC842进行两两组合,分析10组引物对76份种质的区分效率(表3)。

表3 10组引物组合对76份种质的品种区分效率
Table 3 The discrimination rate for 76 accessions of 10 primer combinations

引物组合Primer combination UBC834/ UBC841 UBC834/ UBC842 UBC834/UBC835 UBC834/UBC827 UBC841/UBC842 UBC841/UBC835 UBC841/UBC827 UBC842/UBC835 UBC842/UBC827 UBC835/UBC827谱带数Number of bands 49 48 48 47 47 47 46 46 45 45多态谱带数Number of polymorphic bands 43 42 43 39 25 40 41 39 40 41多态性比率PPB/%87.7 87.5 89.6 93.6 82.9 85.1 89.1 84.8 88.9 91.1最大遗传相似性系数Maximum GS 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00聚类区分效率Cluster discrimination rate/%90.79 90.79 97.37 89.47 88.16 96.05 88.16 90.79 90.79 96.05

从表3可知,10组引物组合的区分效率均高于单引物,区分效率为88.16%~97.37%,其中引物组合UBC834/UBC835的区分效率为97.37%,仅不能区分75号和76号种质(图2),其原因可能是这两份种质的遗传背景差异较小,本研究中所用引物难以鉴别。根据DNA指纹构建的原则,选取引物组合UBC834/UBC835构建76份种质的DNA指纹图谱(图2)。除第75号和第76号外,其他74份种质的DNA指纹图谱均不同,能够被高效准确地鉴定。

图2 76份石榴种质的DNA指纹图谱
Fig. 2 DNA fingerprints of 76 pomegranate germplasm accessions

2.4 山东石榴种质资源的遗传多样性与遗传关系分析

76份种质资源遗传多样性参数分析表明,为1.980 7,Ne为1.651 7,He为0.370 4,I为0.545 1,这表明山东石榴种质资源遗传多样性比较丰富。利用NTSYS2.10软件进行遗传关系聚类,结果表明遗传相似系数GS为0.49~0.98,当GS阈值约为0.688时,将76份石榴种质分为4个类群。

由图3可知,第Ⅰ类群包含40份种质,该类群种质的花色有红色、粉红色,花瓣有单瓣、重瓣等,果实有观赏、食用等多种类型,分类结果与形态分类有较大差异。第Ⅱ类群有27份种质,该类群的花色、果色等形态性状也各异。第Ⅲ类群有2份种质,为峄城小叶2号和峄城单瓣粉红酸石榴。第Ⅳ类群有峄城青皮大籽、白楼无刺等7份种质,这些种质的形态性状也不尽相同。4个类群中,第Ⅲ和第Ⅳ类群的种质与其他种质遗传距离较大,可以选为杂交育种亲本材料,利用杂交优势进行石榴种质资源的遗传改良。

图3 76份种质的UPGMA遗传关系聚类图Fig. 3 UPGMA genetic relationship cluster of 76 accessions

ISSR聚类结果表明同一类群中有些种质的表型性状差异较大,如峄城抗寒砧木1号和峄城竹叶青亲缘关系较近,但性状差异较大;绣球牡丹(75号)和紫皮甜(76号)虽然都属观赏类型,遗传相似系数为0.985,遗传关系最近,但果皮颜色和瓣型都不同,表型性状差异较大。这些结果表明ISSR标记与形态分类结果不一致。在相似系数约为0.678时,第Ⅰ类和第Ⅱ类种质又聚为同一类,包含67份种质,占供试种质总数的88.16%,说明这些种质的遗传关系相对较近。

3 讨 论

关于石榴遗传分析的研究方法主要包括形态学[15]和分子标记[16]。目前,用于石榴遗传多样性、遗传关系研究的DNA标记主要包括RAPD、AFLP、SRAP、ISSR等[17],各种标记的引物多态性不尽相同。Youssef等[18]研究表明,SRAP标记在11个不同石榴品种中的引物多态性平均为74.92%;Faraj等[19]研究表明ISSR在24个石榴品种中呈现79%的引物多态性;Almiahy等[20]研究表明ISSR在不同石榴基因型中的引物多态性为80.6%;Moslemi等[5]研究表明AFLP在67个石榴品种中的多态性为54.13%。本研究中,16个ISSR引物在76份石榴种质中呈现的多态位点比例为88.2%,明显高于前人文献报道的SRAP[18]、AFLP[5]和RAPD[21]的多态性,与Faraj等[19]和Almiahy等[20]的研究结果接近。ISSR标记在其他果树遗传分析中同样展现出优异的多态性特征。对西北喜马拉雅地区50份杏种质资源的遗传变异及群体结构研究显示,ISSR标记检测到83.33%~87.50%的高多态性,精准解析了杏种群的遗传结构[22]。对罗马尼亚本土苹果栽培品种进行研究,ISSR标记多态性达82.3%,可有效用于苹果品种的分子鉴定[23]。本研究中,ISSR标记在石榴中检测到88.2%的高多态性,与杏(83.33%~87.50%)[22]、苹果(82.3%)[23]等的研究结果基本一致。ISSR标记在石榴及其他果树遗传分析中均表现出稳定的高多态性,是种质资源评价的有效工具,未来可结合功能基因组学方法挖掘其在重要性状关联分析中的应用价值。

遗传多样性是评价生物多样性的参考指标之一,物种的遗传多样性越丰富,对环境变化的适应能力就越强。本研究表明山东石榴种质的Ne为1.370 4,He为0.370 4,I为0.545 1,GS为0.49~0.98,与王庆军等[24]、赵丽华等[25]研究的结果相似。76份种质中有67份种质在GS约为0.678时聚为一大类,表明这些山东石榴种质资源的遗传关系较近。为了石榴种质的保存与遗传改良,需要引进外地品种,或者选用遗传关系较远的优良品种(如第Ⅲ和第V类)进行杂交等,以拓宽山东石榴种质的遗传背景、提高多样性。

形态性状分类是通过肉眼对可见性状的异同进行分类,是对基因变异的间接反映,而ISSR是基于DNA层面对基因变异的直接反映。沈进等[26]研究表明石榴品种DNA水平的聚类模式与其发源地和农艺性状无明显相关性。本研究表明ISSR聚类结果与形态学分类不一致,与沈进等[26]结论相一致。这可能是由于长期栽培的人为选育、自然杂交以及品种交换等造成石榴遗传背景比较复杂,形态学特征只是某一性状的外在表现。因此要准确解析种质资源的遗传变异,必须提升到DNA水平,这一观点在多种果树上得到验证。Bădulescu等[23]利用ISSR标记技术评估苹果栽培品种间的遗传变异,ISSR标记成功区分了形态和遗传背景极其相似的Remar和Iris品种,说明该技术能精准鉴定亲缘关系密切的个体基因型。在橄榄种质资源研究中,Raji等[27]证实25株果实性状突出的候选优质橄榄树间存在显著的个体差异,且该差异可通过ISSR标记有效鉴别,其中,CPT14不仅具有独特的形态学特征,其ISSR标记谱型也呈现明显区分度,表明ISSR标记能够精准筛选出形态相似群体中的优异种质,避免了单纯依赖形态可能存在的漏选风险。在杧果遗传多样性研究中,Rocha等[28]证实ISSR标记的遗传分类结果不受地理环境因素的干扰,有效排除了表型因环境不同所造成的形态性状变异,直接从DNA层面揭示了品种间的真实遗传关系。本研究进一步说明ISSR标记同样适用于石榴,能从DNA水平解析其种质的遗传变异和亲缘关系。

DNA指纹图谱构建的方法有多种,如单引物法[29]、引物组合法[30]、特征谱带法[31]等。张安世等[32]采用ISSR技术构建了猕猴桃的DNA指纹,但由于缺乏指纹编码,因此在实际生产应用中受限。王世强等[33]绘制了黄精的SSR指纹,但是复杂的指纹编码限制了实际应用。本研究比较单引物和引物组合对石榴种质的区分效率,结果表明所有单引物均不能将供试种质区分开,最高区分效率为85.53%,而引物组合的区分效率明显高于单引物,最高区分效率为97.37%,仅无法区分2份种质。这一结果与邵雪花等[11]的相似,表明通过优化引物组合可明显提高分子标记的鉴别能力。因此选用引物组合UBC834/UBC835构建了76份种质的DNA指纹图谱,除了75号(绣球牡丹)和76号(紫皮甜)的指纹相同外,其他74份种质的DNA指纹均不相同,具有高度特异性,可用于品种的真实性鉴定。本研究构建的这套ISSR-DNA指纹图谱与形态性状相比能更高效、准确地鉴定石榴种质,为中国石榴指纹数据库的建立提供了理论依据。

4 结 论

本研究证实了ISSR标记能有效解析石榴种质的遗传变异,揭示了山东石榴种质遗传多样性相对丰富,但仍需引进外来优异种质拓宽遗传基础。构建的74份种质DNA指纹图谱具有高度特异性,可用于种质的真实性鉴定。

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Genetic diversity analysis and construction of DNA fingerprint for pome‐granate (Punica granatum L.) germplasm resources in Shandong Province

WU Zhiping1, YANG Yang1, LUO Hua2, MA Li1*

(1College of Life Sciences, Zɑozhuɑng University, Zɑozhuɑng 277160, Shɑndong, Chinɑ; 2Pomegrɑnɑte Reseɑrch Center, Zɑozhuɑng 277300, Shɑndong, Chinɑ)

Abstract:【Objective】Pomegranate (Punicɑ grɑnɑtum L.), distinguished by its exceptional environmental adaptability and extensive cultivation history in China, has emerged as a globally significant economic tree crop. As a primary pomegranate production region within China, Shandong Province faces substantial challenges in germplasm resource management. Being predominantly cross-pollinated, cultivated pomegranates in the region exhibit considerable genetic complexity arising from spontaneous somatic mutations, introductions of germplasm from diverse geographical sources, and extensive varietal exchange. Consequently, this has resulted in pronounced varietal disorganization, ambiguous genetic relationships, and significant lineage confusion, collectively impeding the efficient conservation and utilization of pomegranate germplasm resources. Furthermore, accelerated commercial breeding programs have exacerbated genetic homogenization, rendering conventional morphological identification methods inadequate for precise varietal discrimination and classification. This critical limitation severely constrains the development of elite cultivars and hinders the sustainable advancement of the pomegranate industry. To address these challenges, this study employed Inter-Simple Sequence Repeat (ISSR)molecular markers to investigate the genetic diversity and elucidate the genetic relationships among 76 distinct pomegranate germplasm accessions native to Shandong Province. The primary objective was to construct a robust DNA fingerprinting system, providing scientific foundation for enhancing germplasm preservation, formulating efficient breeding strategies, and achieving precise molecular identification of pomegranate genetic resources. 【Methods】 Experimental materials comprised 76 authenticated pomegranate (Punicɑ grɑnɑtum L.) germplasm accessions systematically curated from the China Pomegranate Germplasm Resources Nursery located in Zaozhuang City, Shandong Province. Genomic DNA was extracted from fresh young leaf tissue using a modified cetyltrimethylammonium bromide (CTAB) protocol. Sixteen ISSR primers with clear amplification bands and high polymorphism were selected for PCR amplification of 76 pomegranate germplasm accessions. PopGene software was used to calculate:Mean number of observed alleles per locus (Na), Effective number of alleles per locus (Ne), Nei’s unbiased gene diversity index (He), and Shannon’s information index (I) for population genetic diversity analysis. The genetic similarity coefficient (GS) was calculated using NTSYS clustering software. The genetic relationships between pomegranate germplasm accessions were analyzed by the Unweighted Pair Group Method with Arithmetic Averages (UPGMA). Based on the UPGMA clustering results, the discrimination efficiency of a single primer or primer combinations for germplasm accessions was evaluated. Primers/combinations capable of distinguishing all accessions were selected to construct DNA fingerprints for the germplasm accessions. 【Results】 A total of 305 loci were detected in 76 accessions using 16 primers, of which 269 were polymorphic loci, with a primer polymorphism ratio of 88.2%.This indicated that the 16 primers exhibited good polymorphism. The results of genetic diversity analysis showed that mean number of observed alleles per locus () was 1.980 7, effective number of alleles per locus (Ne) was 1.651 7, Nei’s unbiased gene diversity index (He) was 0.370 4, and Shannon’s information index (I) was 0.545 1. These metrics collectively demonstrated that moderate to high genetic diversity existed within the sampled Shandong germplasm. UPGMA cluster analysis based on genetic similarity coefficients (GS range:0.49 to 0.98) clustered all 76 accessions into a hierarchical dendrogram. At a GS threshold of 0.688, four distinct genetic clusters emerged:GroupⅠ (n=40):Encompassed accessions with extensive morphological variation, including red/pink flowers, single/double petals, and both ornamental/edible fruit types. Group Ⅱ (n=27):Contained varieties exhibiting diverse pericarp colors and floral characteristics. Group Ⅲ (n=2):Comprised morphologically distinct accessions. Group Ⅳ (n=7):Included varieties with heterogeneous phenotypic traits. Critically, the molecular classification exhibited incongruence with prior morphological taxonomy across all groups. Accessions in Groups Ⅲ and Ⅳ showed the greatest genetic divergence, making them prime candidates for hybrid breeding programs to exploit heterosis and introgress novel genetic variation. Notably, 67 accessions(88.16% of the collection) coalesced into a single cluster at GS=0.678, indicating constrained genetic diversity within the dominant Shandong germplasm. This finding necessitates strategic introduction of genetically distant elite germplasm to broaden the genetic base for sustained breeding progress. According to the UPGMA clustering results, the variety discrimination efficiency of a single primer was 15.78% to 85.52%. No single primer distinguished all 76 accessions, necessitating combinatorial screening. The primer pair UBC834/UBC835 achieved 97.37% discrimination efficiency, generating unique banding profiles for 74 accessions. Only cultivars No. 75 (Hydrangea Peony) and No. 76 (Purple Skin Sweet)shared identical fragment patterns, suggesting either recent divergence or clonal relationship. Consequently, a comprehensive DNA fingerprinting system was established using polymorphic markers from the UBC834/UBC835 combination, enabling unambiguous molecular identification of 74 accessions.【Conclusion】 The 16 ISSR primers used in this study were able to successfully analyze the genetic variation of pomegranate germplasm resources. The genetic diversity of the pomegranate population in Shandong Province was relatively rich, and the ISSR classification results were not consistent with traditional morphological classification. The DNA fingerprints system of 74 accessions established in this study exhibited cultivar-specific characteristics, offering a scientific basis for the scientific classification, precise identification, and breeding of new pomegranate cultivars of pomegranate germplasm resources.

Key words:Pomegranate; ISSR molecular marker; Genetic diversity; DNA fingerprint

中图分类号:S665.4

文献标志码:A

文章编号:1009-9980(2026)03-0547-12

DOI:10.13925/j.cnki.gsxb.20250317

收稿日期:2025-06-19

接受日期:2025-09-02

基金项目:枣庄学院博士科研基金(1020740)

作者简介:吴志苹,女,博士,研究方向为分子生物学。E-mail:wuzhiping288@163.com

*通信作者 Author for correspondence. E-mail:mary1976816@163.com