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【目的】利用相关序列扩增多态性(SRAP)分子标记对来自17个省(区)的31个苦楝种源进行遗传多样性分析,为苦楝种质资源的保存和育种计划的制订提供依据。【方法】通过SRAP分子标记获得1/0数据矩阵,计算SRAP分子标记各项遗传参数,同时进行分子方差分析(AMOVA)。随后计算遗传距离矩阵并进行主坐标分析(PCo A)、邻接法聚类分析(Neighbour-Joining)以及遗传距离和地理距离Mantel相关性分析。【结果】从783对SRAP引物中筛选出的20对引物可扩增出257条清晰的条带,其中145条具有多态性。引物多态性信息指数(PIC)为0.262~0.478,均值为0.385。PIC值较高的10对引物,可扩增出56条特异多态带,可以作为快速鉴别苦楝种源的工具。AMOVA结果显示,38.96%的遗传变异来源于种源间,61.04%的遗传变异来源于种源内。山区的贵州册亨和黎平,云南勐腊和麻栗坡,湖南东安、炎陵和浏阳,四川达州,河北保定,安徽滁州种源的遗传多样性高于其他种源。邻接聚类法根据Nei’s遗传距离将31个种源分为东西2类,西部云南、四川、贵州和甘肃的8个种源构成类群Ⅰ,其他地区的23个种源构成东部类群Ⅱ。类群Ⅱ中北方的济南、保定、泰安、渭南和许昌5个种源聚为一小类,华南地区的屯昌、五指山、钦州和仁化种源聚为一小类,其他相邻和相近的种源大多聚在一起。PCo A分析的种源间双标图结果与邻接法聚类结果基本一致。种源内双标图显示相同种源内的单株大都聚在一起,且种源间和种源内双标图总体分布大体一致。Mantel检验结果表明,种源间遗传距离和地理距离相关性显著(r=0.256,P=0.003)。【结论】SRAP分子标记可以准确、有效地用于苦楝遗传多样性分析。苦楝遗传变异主要来源于种源内,而种源间基因交流有限。种源遗传多样性整体偏低,而部分山区种源遗传多样性较高。在选择高遗传多样性种源的基础上,苦楝选育应侧重种源内家系和单株选择。苦楝种源特征明显,地理环境差异对其遗传多样性具有一定的影响。31个种源大致可分为东西2类,东部种源从北到南有多个聚类中心,其种质资源应采用多点就地保存方式。我国苦楝遗传多样性起源中心或许存在于2类不同种源的生态过渡区。
【Objective】 The genetic diversity of 31 Melia azedarach provenances from 17 provinces (regions) was analyzed by SRAP molecular marker, which provided the basis for conservation and breeding program of Melia azedarach . 【Method】 The 1/0 data matrix was obtained by SRAP molecular markers, and the genetic parameters of SRAP markers were calculated. At the same time, molecular variance analysis (AMOVA) was performed. The genetic distance matrix was then calculated and analyzed by PCo A, Neighbor-Joining, and Mantel correlations between genetic distance and geographic distance. 【Result】 Totally 257 bands were screened from 78 primers selected from 783 SRAP primers, of which 145 were polymorphic. Primer polymorphism information index (PIC) was 0.262 ~ 0.478, with an average of 0.385. The 10 pairs of primers with higher PIC value could amplify 56 specific polymorphic bands, which could be used as a tool to quickly identify the germplasm of Melia azedarach. The results of AMOVA showed that 38.96% of the genetic variation originated from the provenances and 61.04% of the genetic variations originated from the provenances. The genetic diversity of Guizhou Shuiheng and Liping in Guizhou, Mengla and Malipo in Yunnan, Dongan in Hunan, Yanling and Liuyang in Sichuan, Dazhou in Sichuan, Baoding in Hebei and Chuzhou in Anhui were higher than those in other provenances. According to the Nei ’s genetic distance, the 31 adjacent provenances were divided into two categories. The eight provenances from Yunnan, Sichuan, Guizhou and Gansu in the western part of the study were clustered into Ⅰ, and the 23 provenances from other regions constituted the eastern Ⅱ. The five provenances in Jinan, Baoding, Tai’an, Weinan and Xuchang in the north of group Ⅱ are clustered into a small group. Tunchang, Wuzhishan, Qinzhou and Renhua provenances in southern China are clustered into a small group, and other adjacent and similar species Most of the sources come together. The result of PCa analysis between provenances was basically the same as that of the neighbor method. The double-plot within the provenances showed that most of the plants in the same provenance were clustered together, and the overall distribution of double-labeled plots between provenances and provenances was roughly the same. Mantel test showed that there was a significant correlation between provenances and geographic distance (r = 0.256, P = 0.003). 【Conclusion】 SRAP molecular markers can be used accurately and effectively to analyze the genetic diversity of Melia azedarach. The genetic variation of Melia azedarach mainly comes from the provenance, and the gene exchange between the provenances is limited. The genetic diversity of provenances is generally low, while the genetic diversity of some mountain provenances is high. Based on the selection of high genetic diversity provenances, Neem selection should focus on the selection of pedigrees and individuals within the provenance. Neem seed germplasm characteristics are obvious, geographical differences have a certain impact on their genetic diversity. The 31 provenances can be roughly divided into two categories. Eastern provenances have multiple clustering centers from north to south, and their germplasm resources should be preserved in a multi-spot manner. Our country Melia genetic diversity center of origin may exist in two kinds of different provenances of the ecological transition zone.