Simple sequence repeat marker diversity in cassava landraces: genetic diversity and differentiation in an asexually propagated crop
Simple sequence repeat marker diversity in cassava landraces: genetic diversity and differentiation in an asexually propagated crop
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DOI：
10.1007/s00122-003-1348-3
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发表时间：
2003-10-01
影响因子：
5.4
通讯作者：
Kresovich, S
中科院分区：
文献类型：
--
作者：
Fregene, MA;Suarez, M;Kresovich, S
木薯是一种异花授粉、营养繁殖的新热带作物，在热带非洲和东南亚也广泛种植。为了阐明木薯初级和次级多样性中心的遗传多样性和分化及其影响因素，对来自非洲(坦桑尼亚和尼日利亚)和新热带地区(巴西、哥伦比亚、秘鲁、委内瑞拉、危地马拉、墨西哥和阿根廷)的283份木薯地方品种的67个座位的SSR标记变异进行了评估。所有国家的平均基因多样性(即遗传多样性)都很高，平均杂合度为0.5358+/-0.1184。尽管在巴西和哥伦比亚的材料中发现了最高的遗传多样性，但新热带和非洲材料的遗传多样性是可比的。尽管在国家样本中发现了较低的分化水平[F-st(Theta)=0.091+/-0.005]，但单个基因型之间存在足够的遗传距离(共享等位基因的1个比例)，以区分非洲和新热带种质，并揭示非洲地方种质中更明显的亚结构。形成SSR基因座等位基因频率差异的力量，以及可能抵消连续创始人效应的力量，可能涉及自发重组，如亲子关系所评估的那样，以及农民选择适应。
Cassava (Manihot esculenta) is an allogamous, vegetatively propagated, Neotropical crop that is also widely grown in tropical Africa and Southeast Asia. To elucidate genetic diversity and differentiation in the crop's primary and secondary centers of diversity, and the forces shaping them, SSR marker variation was assessed at 67 loci in 283 accessions of cassava landraces from Africa (Tanzania and Nigeria) and the Neotropics (Brazil, Colombia, Peru, Venezuela, Guatemala, Mexico and Argentina). Average gene diversity (i.e., genetic diversity) was high in all countries, with an average heterozygosity of 0.5358 +/- 0.1184. Although the highest was found in Brazilian and Colombian accessions, genetic diversity in Neotropical and African materials is comparable. Despite the low level of differentiation [F-st(theta) = 0.091 +/- 0.005] found among country samples, sufficient genetic distance (1-proportion of shared alleles) existed between individual genotypes to separate African from Neotropical accessions and to reveal a more pronounced substructure in the African landraces. Forces shaping differences in allele frequency at SSR loci and possibly counterbalancing successive founder effects involve probably spontaneous recombination, as assessed by parent-offspring relationships, and farmer-selection for adaptation.