B chromosome polymorphism in maize landraces:: Adaptive vs. demographic hypothesis of clinal variation
B chromosome polymorphism in maize landraces:: Adaptive vs. demographic hypothesis of clinal variation
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DOI：
10.1534/genetics.107.075440
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发表时间：
2007-10-01
期刊：
影响因子：
3.3
通讯作者：
Poggio, Lidia
中科院分区：
文献类型：
--
作者：
Lia, Veronica V.;Confalonieri, Viviana A.;Poggio, Lidia
对阿根廷西北部玉米地方品种的细胞遗传学分析表明，每株植物的平均B染色体（B's）数量存在海拔梯度，生长在较高海拔的品种表现出较高的B's数量。垂直和纵向倾斜经常被解释为选择的证据，然而，它们也可以产生的漂移和空间限制的基因流之间的相互作用，或由混合物之间的先前隔离的人口，有圆锥形到二次接触。在这里，我们测试所观察到的海拔梯度的适应性意义比较分化的水平，平均数的B的，从18个选择性中性位点[简单序列重复（SSR）]之间的7个种群的渐变。替代遗传分化措施的充分性进行了确定，并通过矩阵对应测试评估细胞遗传学，遗传学和海拔距离之间的关联。没有证据表明成对F-ST和海拔距离或B染色体分化之间的关联被found. The对比模式的海拔分歧之间的平均数B的每株和SSR位点的遗传分化表明，人口统计过程不能解释所观察到的水平的分歧的平均数B的。
Cytogenetic analysis of maize landraces from northwestern Argentina has revealed an altitudinal cline in the mean number of B chromosomes (B's) per plant, with cultivars growing at higher altitudes exhibiting a higher number of B's. Altitudinal and longitudinal clines are frequently interpreted as evidence of selection, however, they can also be produced by the interplay between drift and spatially restricted gene flow or by admixture between previously isolated populations that have conic into secondary contact. Here, we test the adaptive significance of the observed altitudinal gradient by comparing the levels of differentiation in the mean number of B's to those obtained from 18 selectively neutral loci [simple sequence repeats (SSRs)] among seven populations of the cline. The adequacy of alternative genetic-differentiation measures was determined, and associations between cytogenetic, genetic, and altitudinal distances were assessed by means of matrix-correspondence tests. No evidence for association between pairwise F-ST and altitudinal distance or B-chromosome differentiation was found. The contrasting pattern of altitudinal divergence between the mean number of B's per plant and the genetic differentiation at SSR loci indicates that demographic processes cannot account for the observed levels of divergence in the mean number of B's.