基于表型性状与SSR分子标记的木薯种质资源遗传多样性分析

Genetic diversity analysis of cassava germplasm resources based on phenotypic traits and SSR molecular markers

  • 摘要: 目的 分析114份木薯种质资源的遗传多样性,为木薯种质资源保存、评价与利用提供理论参考。方法 对114份国内外木薯种质的株高、主茎高、节间长、株型、单株块根数、主茎粗、主茎外皮颜色、主茎内皮颜色、块根表皮等12个表型性状进行遗传多样性分析,并结合SSR荧光分子标记和毛细管电泳方法,评估木薯遗传多样性水平。结果 12个表型性状的变异系数为15.73%~81.74%,平均为39.86%,其中单株鲜薯重的变异系数最大,主茎粗的变异系数最小;12个表型性状的Shannon-Wiener多样性指数为0.5671~2.0059,平均为1.4202,表明供试种质的遗传多样性较高。从12个表型性状中初步筛选出变异系数和Shannon-Wiener多样性指数较高的4个表型性状,分别为主茎高、单株鲜薯重、主茎粗、主茎外皮颜色。基于12个表型性状的聚类结果显示,114份木薯种质在欧式距离为20时被分为六大类,Ⅰ~Ⅲ类分别包含62、38和5份种质,第Ⅳ、Ⅴ和Ⅵ类均包含3份种质。通过28对SSR核心引物对114份木薯种质进行PCR扩增,结果显示,等位基因数(Na)为168个,每对引物检测到的Na为3~14个,平均为6个;有效等位基因数(Ne)为1.5777~7.1136个,每对引物平均检测到的Ne为3.1217个;香农指数(I)为0.6418~2.1958,平均为1.2712;观测杂合度(Ho)为0.2280~0.8070,平均为0.5877;期望杂合度(He)为0.3661~0.8594,平均为0.6444;多态性信息含量(PIC)为0.3205~0.8472,平均为0.5978,表明114份木薯种质资源具有较高的遗传多样性。基于SSR分子标记的聚类结果显示,114份木薯种质分为九大类群,Ⅰ~Ⅸ类群分别包含1、1、13、4、11、7、9、15、53份种质。表型性状聚类结果与SSR分子标记聚类结果不一致,均未表现出明显的地理来源规律。结论 主茎高、单株鲜薯重、主茎粗和主茎外皮颜色是木薯种质资源鉴定和核心种质筛选的重要表型性状,可用于木薯种质资源评价、品种创新和优良种质筛选。114份木薯种质具有较高的遗传多样性,筛选出的28对SSR核心引物能有效分析木薯的遗传多样性,可用于鉴定种质间的亲缘关系。

     

    Abstract: Objective This study aimed to analyze the genetic diversity of 114 cassava germplasm resources, so as to provide a theoretical basis for germplasm resource conservation, evaluation, and utilization.Method Twelve phenotypic traits (including plant height, main stem height, internode length, plant shape, root number per plant, main stem dia-meter, cortex color of main stem, epidermis color of main stem, and root skin) were measured for genetic diversity analysis across 114 Chinese and foreign cassava germplasms, and SSR fluorescent molecular markers and capillary electrophoresis were used to evaluate the genetic diversity of cassava.Result The coefficients of variation (CV) of the 12 phenotypic traits ranged from 15.73% to 81.74%, with an average of 39.86%. The highest CV was observed in fresh root weight per plant, while the lowest was observed in stem diameter. The Shannon-Wiener diversity index values ranged from 0.5671 to 2.0059, with an average of 1.4202, indicating a relatively high overall genetic diversity of the tested germplasms. Four phenotypic traits (main stem height, fresh root weight per plant, main stem diameter, and cortex color of main stem) were preliminarily screened from the twelve phenotypic traits with high CVs and Shannon-Wiener diversity indexes. Cluster analysis based on the 12 phenotypic traits showed that the 114 germplasms were classified into six categories at a Euclidean distance of 20: categories I–III contained 62, 38, and 5 germplasms, respectively, while each of categories IV, Ⅴ and VI contained 3 germplasms. Using 28 pairs of SSR core primers to conduct PCR amplification for the 114 cassava germplasms, a total of 168 alleles (Na) were detected, with 3–14 alleles detected per primer pair (average=6); the effective number of alleles (Ne) ranged from 1.5777 to 7.1136, with an average of 3.1217; Shannon’s index (I) ranged from 0.6418 to 2.1958 (average=1.2712); observed heterozygosity (Ho) ranged from 0.2280 to 0.8070 (average=0.5877); expected heterozygosity (He) ranged from 0.3661 to 0.8594 (average=0.6444); the polymorphic information content (PIC) ranged from 0.3205 to 0.8472, with an average of 0.5978, demonstrating a high genetic diversity among the 114 cassava germplasms. Cluster analysis based on SSR molecular markers divided the cassava germplasms into nine groups: groups I–IX contained 1, 1, 13, 4, 11, 7, 9, 15, and 53 germplasms, respectively. The cluster results for phenotypic traits and SSR molecular markers were inconsistent, and neither pointed to a clear geographic distribution pattern.Conclusion Main stem height, fresh root weight per plant, stem diameter, and cortex color of main stem are important phenotypic traits for germplasm identification and core germplasm screening, which can be applied to germplasm resource evaluation, variety innovation, and elite germplasm screening. The 114 cassava germplasms exhibit a high genetic diversity, and the 28 pairs of SSR core primers could effectively characterize genetic diversity and can be used to analyze relationships among germplasms.

     

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