Isozymic Evidence and the Evolution of Crop Plants
Isozymic Evidence and the Evolution of Crop Plants
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DOI：
10.1007/978-94-009-1840-5_9
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发表时间：
1989
影响因子：
5.1
通讯作者：
J. Doebley
中科院分区：
文献类型：
--
作者：
J. Doebley
自然界中没有任何东西像玉米穗、花椰菜头或装饰性葫芦的奇特雕刻果实那样，与人类的创造有一丝相似之处。虽然这些都是极端的例子，但它们代表了一个多世纪以来令农作物进化论者感到不安的问题，即农作物物种往往在形态上与其最近的野生近缘物种表现出如此广泛的差异，以至于无法确定地建立它们之间的联系。另一个使许多驯化植物的起源变得混乱的问题是野生植物和栽培植物之间杂草中间体的存在。这些是否代表了从栽培中逃逸出来的、栽培种和野生型的杂交衍生物，还是真正的进化中间体？对于不同的作物，这个问题往往有不同的答案。在过去的一个世纪里，作物进化论者使用了各种各样的技术来解开围绕驯化植物的起源和进化的这些和其他谜团。古典分类学、生物地理学、细胞学、考古学和古典遗传学都做出了重要贡献。尽管我们已经了解了很多，但许多作物的起源，甚至是一些最重要的作物的起源仍然不清楚。在本章中，我回顾了同工酶分析对驯化植物起源和进化研究所做出的贡献。这种方法的许多优点经常受到好评：(1) 实验室方法相对简单；(2) 可以以合理的时间和材料成本对许多植物进行分析；(3) 分散在基因组中的众多基因座可作为整个基因组变异的标记；(4) 同工酶的变异水平适合属、种或种群内的研究； (5)如果进行遗传分析，则可以确定电泳可识别的等位基因的频率或存在/不存在。也许同工酶分析在梳理栽培植物进化方面最重要的价值在于，同工酶从未受到人类的直接选择，因此它们提供了作物及其亲属之间相关性的衡量标准，而这种相关性不易因驯化过程而发生严重改变。
There is nothing in nature that faintly resembles such human creations as an ear of corn, a head of cauliflower, or the curiously sculptured fruit of an ornamental gourd. While these are extreme examples, they typify a problem that as unnerved crop evolutionists for over a century, namely that crop species often show such wide morphological departures from their nearest wild relatives that the link between them cannot be established with certainty. Another problem that has muddied the waters surrounding the origin of many domesticated plants is the existence of weedy intermediates between the wild and cultivated forms. Do these represent escapes from cultivation, hybrid derivatives of the cultigen and wild type, or true evolutionary intermediates? The question is apt to have different answers for different crops. Over the past century, crop evolutionists liave employed a diverse arsenal of techniques to unravel these and other mysteries surrounding the origin and evolution of domesticated plants. Classical taxonomy, biogeography, cytology, archaeology, and classical genetics have all made important contributions. Although much has been learned, the origins of many crops, even some of the most important ones, remain obscure.In this chapter, I review the contributions made by isozyme analysis to the study of the origin and evolution of domesticated plants. The many advantages of this approach have been frequently acclaimed:(1) laboratory methods are relatively simple;(2) many plants can be assayed at reasonable cost in time and materials;(3) numerous loci scattered over the genome act as markers for variation in the entire genome;(4) levels of variation in isozymes are appropriate for studies within genera, species, or populations; and (5) if genetic analyses are performed, the frequencies or presence/absence of electrophoretically identifiable alleles can be determined. Perhaps the most significant value of isozyme analysis in sorting out the evolution of cultivated plants is that isozymes were'never under direct human selection, and therefore they provide a measure of relatedness among crops and thein relatives that is not apt to have been severely altered by the domestication process.