Department of Crop Science, North Carolina State University, 27695-7629, Raleigh, NC, USA.
Theor Appl Genet. 1993 Mar;86(1):54-64. doi: 10.1007/BF00223808.
Optimal exploitation of crop genetic resources requires a knowledge of the range and structure of the variation present in the gene pool of interest. Avena sterilis L., the cultivated oat progenitor, contains a store of genetic diversity that is readily accessible to the oat breeder. The objectives of the present paper were: (1) to evaluate isozyme polymorphisms in a sample of A. sterilis accessions from the U.S. National Small Grains Collection, (2) to analyze the distribution of isozyme diversity across the geographic range of the accessions, (3) to classify the accessions into groups based on isozyme variation, and (4) to suggest strategies for efficient sampling of this germplasm collection. One thousand and five accessions from 23 countries and 679 collection sites were screened for variation using 23 enzyme systems. Due to limited information about the genetic relationship among individual members of families of isozymes in hexaploid oat species, data were recorded solely for band presence. The frequencies of bands in accessions from the various countries were used to calculate the probability of genotypic identity (Ix.y), the probability of a unique genotype (Ux.y), and an adjusted polymorphic index (Hx). Accessions from Turkey and Lebanon had the largest polymorphic index values, Turkish and Moroccan accessions displayed the greatest numbers of bands. Accessions from Iran, Turkey, Iraq, and Lebanon had the largest mean probabilities of containing unique genotypes. Based on isozyme data, Turkey appeared to represent the center of diversity in this germplasm collection. Band frequencies calculated among countries were used in a principal component analysis. Accessions from Israel and Morocco clustered together; accessions from Iran, Iraq, Turkey, and Ethiopia formed another group; and Algerian accessions formed an outlying group. Several isozyme bands had a regional distribution. These results suggested that choosing accessions from countries based on their groupings in the principal component analysis should secure a greater range of diversity than sampling from the collection at random. Cluster analyses based on Jaccard's distances calculated for all pairwise combinations of the 1005 accessions revealed six broad genetic groups of accessions. Groups 1 and 6 contained accessions from many countries and encompassed half of all accessions. Groups 2 and 4 were heavily populated by accessions from Israel and Morocco. Groups 3 and 5 were composed almost exclusively of accessions from Iran, Iraq, and Turkey. By selecting representative accessions from these six groups, oat breeders could most effectively sample the range of genetic variation in this A. sterilis collection.
要充分利用作物遗传资源，就必须了解目标基因库中存在的变异范围和结构。栽培燕麦的祖先——野生二粒燕麦（Avena sterilis L.），蕴藏着丰富的遗传多样性，很容易被燕麦育种家所利用。本研究的目的是：（1）评估来自美国国家小谷物收藏的野生二粒燕麦样本中的同工酶多态性；（2）分析等位基因在收集地的地理分布；（3）根据同工酶变异对收集品系进行分类；（4）提出有效抽样的策略。从 23 个国家的 679 个采集点采集了 1050 个品系进行变异筛选，共使用了 23 种酶系统。由于关于六倍体燕麦属中同工酶家族的各个成员之间遗传关系的信息有限，数据仅记录为带的存在。利用各国品系的带型频率计算基因型相同的概率（Ix.y）、独特基因型的概率（Ux.y）和调整后的多态性指数（Hx）。来自土耳其和黎巴嫩的品系具有最大的多态性指数值，土耳其和摩洛哥的品系显示出最多的带型。来自伊朗、土耳其、伊拉克和黎巴嫩的品系具有最大的独特基因型概率均值。基于同工酶数据，土耳其似乎是该种质资源库中多样性的中心。各国之间的带型频率用于主成分分析。来自以色列和摩洛哥的品系聚在一起；来自伊朗、伊拉克、土耳其和埃塞俄比亚的品系形成另一组；阿尔及利亚的品系则形成一个外围组。一些同工酶带具有区域性分布。这些结果表明，根据主成分分析中的分组选择来自各国的品系，应该比随机抽样获得更大的多样性范围。基于所有 1005 个品系两两组合的 Jaccard 距离计算的聚类分析揭示了 6 个广泛的遗传分组。第 1 组和第 6 组包含来自许多国家的品系，涵盖了所有品系的一半。第 2 组和第 4 组主要由来自以色列和摩洛哥的品系组成。第 3 组和第 5 组几乎完全由来自伊朗、伊拉克和土耳其的品系组成。选择来自这 6 个组的代表性品系，燕麦育种家可以最有效地在该野生二粒燕麦收集品系中采样遗传变异范围。
