大蕉特异性分子靶标的开发及其评价

王 芳,崔广娟#,吕 顺*,曾莉莎,陈东仪,黄晓彦,曾国玲,刘文清,何建齐

(东莞市农业科学研究中心,广东东莞 523000)

摘 要:【目的】由于香蕉高度不育和无性繁殖,经过长期的进化,导致许多资源来源不清晰。开发大蕉资源特异性分子靶标,为香蕉资源鉴定和遗传改良提供技术支撑。【方法】利用香蕉线粒体cox2/2-3基因序列,根据大蕉在该序列的特异性位点进行分子靶标设计,采用37份大蕉,以及香牙蕉、粉蕉、贡蕉、尖苞片蕉(Musa acuminata)、长梗蕉(M.balbisiana)、芭蕉(M.basjoo)以及阿宽蕉(M.itinerans)等共计59份其他类型香蕉资源进行鉴定筛选,获得特异性鉴定大蕉的分子靶标DcR/DcF,并进行评价。【结果】通过对共计96份香蕉资源的检测,发现37份大蕉均出现634 bp特异性条带,香牙蕉、粉蕉、贡蕉未出现该条带。在应用该标记对野生蕉检测中发现仅有阿宽蕉出现该特异性条带,长梗蕉、尖叶蕉、芭蕉均未出现该特异条带,同时大蕉和阿宽蕉的杂交后代出现了该特异条带。【结论】成功开发了一个大蕉特异性分子靶标DcR/DcF,可以在栽培蕉中特异性地鉴定大蕉,并具有快速、简便、准确的特点,该技术对香蕉种质资源鉴定、新品种选育等具有重要的应用价值。

关键词:大蕉;分子靶标;特异性鉴定,线粒体基因,评价

香蕉(Musa spp.)是芭蕉科(Musaceae)芭蕉属(Musa L.)植物,不仅是世界上重要的水果之一,更是世界第四大粮食作物,全球4 亿人的主食[1-2]。香蕉栽培种主要是由尖苞片蕉Musa acuminata Colla.(记为A基因组)和长梗蕉M.balbisiana Colla.(记为B 基因组)这两个原始野蕉种内或种间杂交后代演化发展而来的[3]。香蕉属于无性繁殖,高度不育,经过长期的栽培,再加上不同地域之间的交流,导致了许多来源不明的品种和资源,并且出现了很多同名异种和同种异名的现象[4-6],这种情况给香蕉种质资源的鉴定和遗传育种的研究带来了很多困难。1955年,Simmonds等[7]根据不同香蕉品种的形态,包括叶片、蕉蕾和假茎等相关性状,结合染色体倍性,将栽培蕉分为了AA、BB、AB、AAA、AAB、ABB、AAAA、AAAB、AABB、ABBB。在之后广大学者的研究中,不断地补充和完善该种分类方法。然而,仅通过这些形态性状判定并不精确,并且该方法难以准确反映不同基因型香蕉的基因组来源和组成[8]。之后的研究结果证实了这一点,利用形态特征和分子标记技术手段,发现了香蕉中还具有不同于A 和B 基因组的其他基因组,如有的香蕉品种带有S(M.Schizocarpa)或者T(M.Textilis)基因组的特征[9-10]

据报道,我国香蕉的种质资源间的遗传多样性比较丰富,种类繁多[11],栽培蕉主要有香牙蕉(AAA)、粉蕉(ABB)、粉大蕉(ABB)、大蕉(基因型不确定)、龙牙蕉(AAB)、贡蕉(AA)等[12]。而形态分类法在调查研究时工作量大,并且耗费时间久,容易受环境影响,存在一定的主观性,因此需要进一步发展其他更可靠的研究方法。随着科学技术的进步、分子生物学的快速发展,各类分子标记已经被应用于分析香蕉品种(系)的种群鉴定与分类、遗传多样性研究[13-16],利用分子手段研究香蕉的基因组可以更直观地呈现,并且分子生物技术手段的出现加速了植物品种改良进程[17]。笔者研究团队前期收集了大量我国各香蕉产区的大蕉资源,在对香蕉线粒体基因片段cox2/2-3 序列的研究中(论文尚未发表),发现大蕉的该序列具有特异性,根据这段序列设计了可以特异性鉴定大蕉的靶标引物,并对其检测效果进行了分析评价,以期为香蕉种质资源的鉴定和新品种的选育提供更加快速精准的技术手段。

1 材料和方法

1.1 试验材料

于2019 年3—6 月采样于东莞市农业科学研究中心万江基地香蕉资源圃以及广东省农科院果树所国家果树种质广州香蕉荔枝圃。其中杂1、杂2、杂4为大蕉和阿宽蕉类野蕉的杂交后代。

1.2 方法

1.2.1 香蕉基因组的DNA 提取 选取香蕉无病虫害的嫩叶,分别进行DNA 提取。DNA 提取方法采用十六烷基三甲基溴化铵(cetyltrimethylammonium bromide,CTAB)法[18]

1.2.2 特异性序列测序 目的片段扩增:采用线粒体基因组中细胞色素氧化酶亚基Ⅱ基因中的1个内含子(cox2/2-3),PCR反应体系及电泳检测参考Duminil等[19]的方法。

目的片段测序:cox2/2-3 片段经DNA 胶回收试剂盒回收纯化后,克隆到pMD18-T 载体中,阳性克隆送至Ⅰnvitrogen 公司广州分公司测序。为确保测序结果的准确性,分别用引物对每个扩增片段进行正反链测序,将两条链比对拼接。

1.2.3 特异性靶标引物设计及PCR 扩增 采用MEGA 5 进行序列比对;引物设计采用Primer premier 5.0,并对PCR 退火温度及体系中DNA 模板和酶量进行优化;检测采用琼脂糖凝胶电泳。

1.2.4 香蕉资源的鉴定评价 采用1.2.3引物及扩增检测方法,进行96个香蕉资源(表1,表2)的鉴定评价。

表1 60 份不同类型的栽培蕉资源
Table 1 Sixty cultivated banana resources of different types

编号Code 品种名Accession name 来源Origin 类型Type 1 2 3 4 5 6 7 8 9 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 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53矮大蕉Ai Dajiao巴马大蕉Bama Dajiao畦头大蕉Qitou Dajiao番禺大蕉Panyu Dajiao华农中把大蕉Huanong Zhongba Dajiao东莞中把大蕉Dongguan Zhongba Dajiao东莞抗病大蕉Dongguan Kangbing Dajiao潮州大蕉Chaozhou Dajiao防城大蕉Fangcheng Dajiao封开大蕉Fengkai Dajiao高脚大蕉Gaojiao Dajiao高州中把大蕉Gaozhou Zhongba Dajiao广西中把大蕉Guangxi Zhongba Dajiao海南中把大蕉Hainan Zhongba Dajiao四川大蕉Sichuang Dajiao沙田大蕉Shatian Dajiao顺德中把大蕉Shunde Zhongba Dajiao三江大蕉Sanjiang Dajiao桂平大蕉Guiping Dajiao永州大蕉Yongzhou Dajiao雷高大蕉Leigao Dajiao龙华大蕉Longhua Dajiao美大蕉Mei Dajiao海南酸大蕉Hainan Suan Dajiao罗坝大蕉Luoba Dajiao东莞高把大蕉Dongguan Gaoba Dajiao中山中把大蕉Zhongshan Zhongba Dajiao景洪野大蕉Jinghong Ye Dajiao海南芭蕉Hainan Bajiao饭芭蕉Fan Bajiao牛奶蕉Niu Nai Jiao木棉蕉Mu Mian Jiao柴蕉Chai Jiao海南牛角蕉Hainan Niujiao Jiao兴隆酸蕉Xinglong Suanjiao长果牛角蕉Changguo Niujiao Jiao云南牛角蕉Yunnan Niujiao Jiao杂1 Za 1杂2 Za 2杂4 Za 4 8818-1北大矮蕉Beida Aijiao大丰1号Dafeng No.1大蜜舍Gros michel大南香蕉Danan Xiangjiao登科1号Dengke No.1中粉1号Zhongfen No.1志满粉蕉Zhiman Fenjiao三亚粉蕉Sanya Fenjiao FJ-20 FJ-30 FJ-HR粉杂1号Fenza No.1广东Guangdong HRⅠ/GXAASⅠFTR/GDAASⅠFTR/GDAAS广东Guangdong广东Guangdong广东Guangdong广东Guangdong HRⅠ/GXAASⅠFTR/GDAASⅠFTR/GDAAS广东GuangdongⅠFTR/GDAASⅠFTR/GDAASⅠFTR/GDAASⅠFTR/GDAASⅠFTR/GDAASⅠFTR/GDAAS HRⅠ/GXAAS湖南HunanⅠFTR/GDAASⅠFTR/GDAASⅠFTR/GDAASⅠFTR/GDAAS广东Guangdong广东GuangdongⅠFTR/GDAAS云南YunnanⅠFTR/GDAASⅠFTR/GDAASⅠFTR/GDAASⅠFTR/GDAAS福建FujianⅠFTR/GDAAS SSCR/CATAS云南YunnanⅠFTR/GDAAS DGARC DGARC DGARC SSCR/CATAS海南HainanⅠFTR/GDAASⅠFTR/GDAASⅠFTR/GDAAS福建FujianⅠFTR/GDAAS SSCR/CATAS海南Hainan广东Guangdong广东Guangdong广东GuangdongⅠFTR/GDAAS大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉Dajiao大蕉×阿宽蕉Dajiao×Akuanjiao大蕉×阿宽蕉Dajiao×Akuanjiao大蕉×阿宽蕉Dajiao×Akuanjiao香牙蕉AAA Cavendish香牙蕉AAA Cavendish香牙蕉AAA Cavendish大蜜舍AAA Gros michel香牙蕉AAA Cavendish香牙蕉AAA Cavendish粉蕉ABB Pisang Awak粉蕉ABB Pisang Awak粉蕉ABB Pisang Awak粉蕉ABB Pisang Awak粉蕉ABB Pisang Awak粉蕉ABB Pisang Awak粉蕉ABBB Pisang Awak

表1 (续) Table 1 (Continued)

注:ⅠFTR/GDAAS.广东省农业科学院果树研究所;HRⅠ/GXAAS.广西农业科学院园艺研究所;DGARC.东莞市农业科学研究中心;SSCR/CATAS.中国热带农业科学院南亚热带作物研究所。下同。
Note: ⅠFTR/GDAAS.Ⅰnstitute of Fruit Tree Research, Guangdong Academy of Agricultural Sciences; HRⅠ/GXAAS.Horticultural Research Ⅰnstitute, Guangxi Academy of Agricultural Sciences; DGARC.Dongguan Agricultural Research Centre; SSCR/CATAS.South Subtropical Crops Research Ⅰnstitute of Chinese Academy of Tropical Agricultural Sciences.The same below.

编号Code 品种名Accession name 来源Origin 类型Type 54 55 56 57 58 59 60琼州南平粉蕉Qiongzhou Nanping Fenjiao白粉1 Baifen No.1紫茎蕉S Zijingjiao S贡蕉Gongjiao贡选Gongxuan佳丽Jiali佛手S Foshou S海南Hainan广东GuangdongⅠFTR/GDAASⅠFTR/GDAAS DGARCⅠFTR/GDAAS福建Fujian粉蕉ABB Pisang Awak粉蕉ABBB Pisang Awak龙牙蕉Longyajiao贡蕉Gongjiao贡蕉Gongjiao贡蕉Gongjiao贡蕉Gongjiao

表2 36 份不同种的野生蕉资源
Table 2 Thirty-six wild banana resources of different species

编号Code 1 2 3 4 5 6 7 8 9 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 35 36品种名Accession name美叶芭蕉Mei Ye Ba Jiao小果野蕉Xiao Guo Ye Jiao景洪小果野蕉Jinghong Xiao Guo Ye Jiao华南BB野蕉Huanan BB Ye Jiao五山野蕉Wushan Ye Jiao BB4 BB3湛江BB Zhanjiang BB天宝野蕉Tianbao Ye Jiao芭蕉Bajiao沐阳芭蕉Shuyang Bajiao商洛芭蕉Shangluo Bajiao泗阳芭蕉Siyang Bajiao板蕉Banjiao五指山野生蕉1号Wuzhishan Yeshengjiao 1广宁野生蕉Guangning Yeshengjiao陵水野生蕉Lingshui Yeshengjiao增城野生蕉Zengcheng Yeshengjiao尖峰岭野生蕉Jianfengling Yeshenjiao永州野生蕉Yongzhou Yeshengjiao龙州野生蕉Longzhou Yeshengjiao三明野生蕉Sanming Yeshengjiao五指山野生蕉3号Wuzhishan Yeshengjiao 3阿宽蕉Aquan Jiao宝山3号Baoshan No.3博白野生蕉Bobai Yeshengjiao博罗野生蕉Boluo Yeshengjiao楚洪野生蕉Chuhong Yeshengjiao贺州野生蕉Hezhou Yeshengjiao红河阿宽蕉Honghe Aquan Jiao黎母野生蕉Limu Yeshengjiao龙岩野生蕉Longyan Yeshengjiao融水野生蕉Rongshui Yeshengjiao帽子峰野生蕉Maozifeng Yeshengjiao盛宽Shengkuan武功山野生蕉Wugongshan Yeshengjiao品种来源Origin不详UnknowⅠFTR/GDAAS云南Yunnan广东GuangdongⅠFTR/GDAAS DGARC DGARC广东Guangdong福建FujianⅠFTR/GDAAS江苏Jiangsu陕西Shaanxi江苏Jiangsu四川Sichuan海南Hainan广东Guangdong海南Hainan广东Guangdong海南Hainan湖南Hunan HRⅠ/GXAAS福建Fujian海南HainanⅠFTR/GDAAS云南Yunnan广西Guangxi广东Guangdong云南Yunnan广西Guangxi云南Yunnan海南Hainan福建Fujian广西Guangxi广东Guangdong广东Guangdong江西Jiangxi种Species尖苞片蕉M.acuminata尖苞片蕉M.acuminata尖苞片蕉M.acuminata长梗蕉M.balbisiana长梗蕉M.balbisiana长梗蕉M.balbisiana长梗蕉M.balbisiana长梗蕉M.balbisiana长梗蕉M.balbisiana芭蕉M.basjoo芭蕉M.basjoo芭蕉M.basjoo芭蕉M.basjoo芭蕉M.basjoo阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans阿宽蕉M.itinerans

2 结果与分析

2.1 香蕉基因组DNA的提取

采用改良CTAB 法提取香蕉叶片DNA,用Bio-Drop μLite(超微量蛋白核酸分析仪)检测其质量浓度和纯度,DNA 质量浓度为500~1000 ng·μL-1,OD260/OD280=1.8~2.0,质量较好,符合试验要求;

根据测得的浓度,吸取适量体积的DNA 样品,稀释成质量浓度50 ng·μL-1的工作液备用。

2.2 香蕉cox2/2-3基因测序

采用cox2/2-3 基因对不同香蕉资源进行分析,不同香蕉资源该片段大小在750~1200 bp;大蕉与其他香蕉资源相比,基因片段最长,约1200 bp,大蕉的序列基本一致,序列为:TATGAGAGCCTTTCA GCTCGTACTGCTCACACTCCTAGATCTGAACTA AGAGACCTCTGCGACCATAGTTTGAGCTGGGA GTTGCTCCTAGAATCCTTCCAAATGAGCTTGAA AGTCAACGTCAACAACACGAAAAGTACACGTT GGTTGCCTACTAATCAGATAATAGGTGAAATCC CTTCGCCTCTCGGAAGCTTGAAAGGGAGCTGA AAGTTTAGGGTGAGAAAGGTGAGAAAAGAGA TTAGCTGGAGGTAGGGCGGGTCCTGAAACTAA GGTGTACATACATCAAAGCAGATTATGTCGGTA TCCTTCCAATCCATATTGACCGGTATGTCGGTAT CCTTCCAATCCATATTGACCGGGAAGAGTGGG GAGGCTAATGCAGAAGTATCTATGTATTAGAGA GATCCCTTATATTGATGATTGCTGGCTTCCCGG ACTTGTCACAGATGGCTAGGAAGAAGAATAGG AGAAGTAGTCTCTGCCGTAGCAGGTCCTTCTCCTGTAGCTAAGACTGCCCTTACTTTGATTATTG TTCGTTCAGTTCACCGCGGCACTAATGAATAA GCTTGAGAATAACTTAGAGTGGCGCCTAACCT TTGAGAGCGTCTCTTGTCTTTGAATTTCAGAAG AAGAGTTGTAGATCTTGGACTGGCCCCCTTCG CATGACCTAGAATGAAAGGTCTGTGCTACTATA AGGCCTCTAAACTCCTTCCTCAGGACACTGTT GCGTTGCCATGGGACGGGGTATCCCCGACTTC TATAGTTCCTTGGTTCGACCTCCTAATGAGAAT TGAGGTCCTTGCGCGGGCGTCTCATCCCTAAG ACGAGTTTGCCTTTGTTTGTATGGAGTGTCCCG TGGTTACTCTAGTGCCAGCCGCAGAGAGGAAT GCCATCAACTAGGGCGCTATTTGCCACTAACCA CTCGCTCTTAGGCCGCCAATTAATACCTCCTCC GCGTTTCAAGTTGGTTATCCTAACCATTTCCCC TGCTCTACCGGGAGCCTGGCCCAATATTCGATC TTATATACTGCCTTGCTCCTCGGCTCCCTACTGC TCAAGCGGCTCGCTGTAATAGCTTGCTTATCGG GTGGCTCGCACCCCGACCACGGGTGGTGCGGC TAAGCCAGAGTGGGCTCAGCTGTCGGCCTATG TATCCGG。

2.3 特异性靶标引物设计及检测方法

通过对东莞中把大蕉、华农中把大蕉、8818-1、北大矮、中粉1 号、粉杂1 号、贡蕉、贡选等8 个香蕉资源cox2/2-3 核苷酸序列的比对,发现在该基因229~985 bp 处,大蕉存在9 处的插入突变(图1),共计175 bp,可以进行特异性靶标引物设计。根据大蕉cox2/2-3 核苷酸序列的特异性,设计了1 对引物,上游引物为DcR:TATTGACCGGTATGTCGGTA;下游引物为DcF:AGGTATTAATTGGCGGCCTAA。上游引物位于336~355 bp处;下游引物位于948~969 bp处(见图1黑色方框)。

图1 大蕉cox2/2-3 基因的主要突变位点分布(从第229 bp-985 bp)
Fig.1 Distribution of main mutation sites of cox2/2-3 gene of Dajiao from 229 bp to 985 bp

1.东莞中把大蕉;2.华农中把大蕉;3.8818-1;4.北大矮蕉;5.中粉1 号;6.粉杂1 号;7.贡蕉;8.贡选。
1.Dongguan Zhongba Dajiao;2.Huanong Zhongba Dajiao;3.8818-1;4.Beida Aijiao;5.Zhongfen No.1;6.Fenza No.1;7.Gongjiao;8.Gongxuan.

经过优化获得最优的PCR 程序:94 ℃预变性3 min;94 ℃变性30 s,60 ℃退火30 s,72 ℃延伸1 min,循环30 次;72 ℃延伸10 min;其最优的PCR体系:10×PCR 反应缓冲液2.5 μL、2.5 nmol·L-1 dNTPs 2 μL、10 μmol·L-1引物各1 μL、50 ng·μL-1模板DNA 1 μL、5 U·μL-1 TaqDNA 聚合酶[TⅠANGEN,天根生化科技(北京)有限公司]0.5 μL,灭菌双蒸水补足体积至25 μL;最优检测方法为:1.2%琼脂糖凝胶、电极缓冲液为0.5×TBE、110 V 电压电泳30 min。

2.4 特异性靶标的PCR扩增

对46份不同基因型的香蕉资源进行分析,分别选用部分大蕉和香牙蕉、粉蕉、贡蕉等栽培蕉和BB、AAw、basjoo类野蕉类进行对比检测,结果显示只有大蕉在634 bp 处出现特异的条带,而其余蕉类均没有条带出现(图2、图3)。

图2 部分大蕉和香牙蕉、粉蕉等不同基因型香蕉对比检测
Fig.2 Comparison of Dajiao and different genotypes of cultivated banana resources

M.2000 bp marker;1~23 号样品为表1 中1~6、41~56 号及表2 中1 号样品。
M.2000 bp marker;Samples 1-23 are the samples No.1-6,41-56 in Table 1 and No.1 in Table 2.

图3 部分大蕉、贡蕉和BB、AAw、basjoo 类野生蕉对比检测
Fig.3 Comparison of Dajiao,Gongjiao and different genotypes of wild banana resources

M.2000 bp marker;1~23 号样品为表1 中7~12、57~60 号及表2 中2~13 号样品。
M.2000 bp marker;Samples 1-23 are the samples No.7-12,57-60 in Table 1 and No.2-13 in Table 2.

2.5 扩大群体进行特异性靶标引物准确性的检测

对37份大蕉资源以及3个杂交种进行特异性扩增,所有供试大蕉品种均出现634 bp特异性条带(图4、图5)。杂1、杂2、杂4 为大蕉和阿宽蕉的杂交后代,这3 份资源也出现了634 bp 特异性条带(图4),检测准确率100%。

图4 部分大蕉检测结果
Fig.4 Test results of 24 Dajiao resources

M.2000 bp marker;1~24 号样品为表1 中1~24 号样品。
M.2000 bp marker;Samples 1-24 are the samples No.1-24 in Table 1.

图5 部分大蕉和杂交品种的检测结果
Fig.5 Test results of 13 Dajiao resources and 3 hybrids

M.2000 bp marker;1~16 号样品为表1 中25~40 号样品。
M.2000 bp marker;Samples 1-16 are the samples No.25-40 in Table 1.

2.6 利用特异性靶标引物对阿宽蕉类野蕉的检测

对从我国各地收集的22 份阿宽蕉类野蕉资源进行特异性扩增,所有供试品种均出现634 bp 特异性条带(图6)。

图6 阿宽蕉类野蕉检测结果
Fig.6 Test results of 22 wild banana resources of M.itinerans

M.2000 bp marker;1~22 号样品为表2 中15~36 号样品。
M.2000 bp marker;Samples 1-22 are the samples No.15-36 in Table 2.

3 讨 论

近年来,应用单个或多个分子标记技术来鉴定香蕉种质资源的研究逐渐增多[20-23],但是多数是针对不同香蕉基因组的鉴定,而对某一类香蕉的快速鉴定分子标记研究比较少。本研究利用cox2/2-3基因序列,根据大蕉在序列上的特异性位点进行大蕉特异性分子靶标设计,获得了可以在香蕉栽培种中特异性鉴定大蕉的一对引物,具有快速、简便、准确的特点,该类分子标记对香蕉种质资源鉴定、新品种选育等具有重要的应用价值。

研究表明,根据香蕉的植株形态和经济性状,栽培蕉主要分为香牙蕉、龙牙蕉、粉蕉、大蕉、粉大蕉、和贡蕉等[12]。国内易把我国大蕉和国外煮食蕉中作粮食用的饭蕉(Plantain,AAB)混淆[24-25],我国的大蕉一般鲜食用,不同于国外的饭蕉。受到消费市场的限制,大蕉的种植相对较少,传播范围也较小,对其研究不多,但是我国的大蕉具有抗病、高产、耐贫瘠、抗寒等多个优点[26-29]。大蕉大多为三倍体,具有单性结果和高度不育性。目前研究表明少量三倍体的栽培品种具有较微弱的雌性可育性[30-32],其中大蕉与野生蕉杂交可少量结籽[33]。笔者研究组也开展了相关杂交试验,大蕉和尖苞片蕉、长梗蕉及阿宽蕉等野生蕉杂交均能结籽,结籽率较低。可见我国大蕉是一类具有特殊性及重要研究利用价值的香蕉种质资源。通常,国内外学者普遍认为大蕉是ABB 基因型,与粉蕉的基因型一致;但是王正询等[34]通过对广东大蕉的形态、染色体配对及核型分析,认为是BBB型;也有研究人员通过形态学指标观察、测量,按照“Simmonds”标准分类法评分,结合染色体计数,判定三江大蕉基因型为AAB[35];笔者研究组按照“Simmonds”标准分类法对香蕉品种资源表型基因型进行调查和评价,大部分大蕉的得分介于AAB与ABB 之间,偏向AAB,利用流式细胞技术对香蕉倍性分析结果显示大蕉DNA 相对含量(或倍性值)与其他ABB基因型资源有一定差异,基因组更大一些[36]。笔者在本研究中通过分析发现该来源于线粒体的大蕉分子靶标在栽培种香蕉资源中只有大蕉出现特异性条带,在野生种香蕉资源中仅有阿宽蕉类野蕉出现了该特异性条带,同时以大蕉为母本、阿宽蕉为父本获得的杂交种也出现了该特异性条带,而香蕉具有线粒体父本遗传的独特遗传方式[37],因此推测阿宽蕉类野蕉与大蕉的父本来源存在一定的关系。

4 结 论

栽培蕉遗传背景狭窄,病虫害高发,亟须引入新的遗传基因,杂交育种是根本、有效的途径。目前国内育种者开始尝试香蕉杂交育种,从大量的杂交后代中筛选优良种质,工作量大、周期长,精确高效的早期筛选技术对杂交种的鉴定和筛选十分重要,目前这方面的研究还比较少,笔者在本研究中成功开发了一个大蕉特异性分子靶标(DcR/DcF),可以在栽培蕉中特异性地鉴定大蕉,并具有快速、简便、准确的特点,该特异性分子靶标为具有多种优异性状的大蕉类资源的应用提供了技术支撑,该类技术的开发在香蕉改良工程中具有重要的意义。

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Development and evaluation of specific molecular target of Dajao

WANG Fang, CUⅠGuangjuan#, LÜ Shun*, ZENG Lisha, CHEN Dongyi, HUANG Xiaoyan, ZENG Guoling,LⅠU Wenqing,HE Jianqi

(Dongguan Agricultural Research Centre,Dongguan 523000,Guandong,China)

Abstract:【Objective】Banana is an important fruit and food crop in the world,but it is facing the technical bottleneck of resource identification and genetic improvement.Banana plants are asexual and highly sterile.Because of long-term cultivation and exchanging between different regions,the origin of banana varieties is not clear.China has abundant cultivated and wild banana resources.Dajiao(Musa)is one of widely distributed banana resources in China which is different from plantain abroad, and there are many different types of Dajiao in different growing areas.Dajiao has many advantages,such as high yield,cold resistance,and strong disease resistance,so Dajiao is an important genetic resource.The aim of this study was to develop a specific molecular target of Dajiao for the rapid identification and genetic improvement of Chinese banana resources.【Methods】The 96 samples of different banana resources used in this experiment included 6 cultivars of Cavendish, 9 cultivars of Pisang Awak, 1 cultivar of Longya banana,4 cultivars of Pisang Mas,37 cultivars of Dajiao,3 wild resources of Musa acuminata,6 wild resources of Musa balbisiana,5 wild resources of Musa basjoo,21 wild resources of Musa itinerans and 3 hybrids, which were collected from different producing areas of China.The genomic DNA from each sample was isolated from fresh young cigar leaves using CTAB method.The concentration and purity of each DNA were checked with BioDrop μLite.First, we selected eight varieties of four groups, including Huanong Zhongba Dajiao, Dongguan Zhongba Dajiao, 8818-1, Beida Aijiao, Zhongfen No.1, Fenza No.1, Gongjiao and Gongxuan as representatives, through cloning and sequencing of the mitochondrial gene cox2/2-3, and aligning the sequences by Mega 5.0.We found the specific base sequence in Dajiao from the results.Then Primer Premier 5.0 was used to design the specific primer,the optimal PCR amplification system and agarose gel electrophoresis detection method were optimized.At last,we obtained the specific detection target through a certain range of screening and expanded range of validation.【Results】The concentration of DNA extraction reached 500-1000 ng·μL-1,OD260/OD280 = 1.8-2.0, and the quality was good, which met the requirements of the experiment.The DNA was finally diluted into 50 ng·μL-1 and used for the experiments.PCR amplification of the cox2/2-3 region produced a single fragment of about 750-1200 bp in all the samples, and the gene fragment of Dajiao was longest, about 1200 bp.Through comparing the gene sequence of eight banana resources,we found 9 different insertional mutations (175 bp in total) in Dajiao, located at 229-985 bp of this gene.The abundant variation facilitated the design of specific primers.According to the specificity of cox2/2-3 gene sequence in Dajiao,a pair of primers was designed,the forward primer was DCR:TATTGACCGGTATGTCGGTA, and the rewerse primer was DCF: AGGTATTAATTGGCGGCCTAA.The optimal PCR procedure was: 94 ℃predenaturation for 3 min, 94 ℃denaturation for 30 s, 60 ℃annealing for 30 s,72 ℃extension for 1 min,30 cycles,72 ℃extension for 10 min,94 ℃denaturation for 30 s,60 ℃annealing for 30 s,72 ℃extension for 10 min.The optimal PCR system was:10×PCR reaction buffer 2.5 μL,2.5 nmol·L-1 dNTPs 2 μL,10 μmol·L-1 primer 1 μL,50 ng·μL-1 template DNA 1 μL,5 U·μL-1 TaqDNA polymerase 0.5 μL, the volume was replenished to 25 μL with sterilized double-distilled water.The optimal detection method was: 1.2% agarose gel, 0.5×TBE electrode buffer, 110 V electrophoresis for 30 min.Through the examination,a 634 bp specific band was found in all 37 banana resources of Dajiao,but not in banana resources of Cavendish,Pisang Awak,Pisang Mas and Longyajiao.The target band was clear, no miscellaneous band and the detection accuracy was 100% in cultivated species.Only M.itinerans showed this specific band in the detection of wild banana using this marker,no specific band was found in M.acuminata,M.balbisiana and M.basjoo.At the same time,the specific band appeared in 3 hybrid progenies,so this fragment would be also suitable for the identification of hybrid progenies from Dajiao × M. itinerans.Banana had a unique inheritance mode of mitochondrial paternal inheritance as reported early, and this specific molecular target was derived from mitochondrial genes.On the whole,the 634 bp special band appeared in 37 cultivars of Dajiao and 22 wild resources of M. itinerans, so there should be a certain relationship between the paternal origin of Dajiao and M. itinerans.【Conclusion】Compared with traditional evaluation method using morphological markers,this specific molecular target of Dajiao would be more stable,sensitive and accurate and could be efficiently used in selection of parents and early identification of hybrid offspring in cross breeding,the results of this study about Dajiao and M. itinerans would provide information for studying the origin and evolution of bananas.

Key words:Dajiao;Molecular target;Specificity identification;Mitochondrial gene;Evaluation

中图分类号:S668.1

文献标志码:A

文章编号:1009-9980(2023)12-2661-11

DOⅠ:10.13925/j.cnki.gsxb.20230343

收稿日期2023-09-05

接受日期:2023-10-23

基金项目东莞市2021年度省乡村振兴战略专项资金“大专项+任务清单”(20211800400052);广东省级农业科技创新及推广项目-香蕉菠萝产业技术体系创新团队(2023KJ109);广东省基础与应用基础研究基金项目(2022A1515140114)

作者简介王芳,女,正高级农艺师,硕士,研究方向为香蕉分子生物技术。E-mail:29333689@qq.com。#为共同第一作者。崔广娟,女,硕士,研究方向为分子育种。

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