Tanksley S D, Ganal M W, Prince J P, de Vicente M C, Bonierbale M W, Broun P, Fulton T M, Giovannoni J J, Grandillo S, Martin G B
Department of Plant Breeding and Biometry, Cornell University, Ithaca, New York 14853.
Genetics. 1992 Dec;132(4):1141-60. doi: 10.1093/genetics/132.4.1141.
High density molecular linkage maps, comprised of more than 1000 markers with an average spacing between markers of approximately 1.2 cM (ca. 900 kb), have been constructed for the tomato and potato genomes. As the two maps are based on a common set of probes, it was possible to determine, with a high degree of precision, the breakpoints corresponding to 5 chromosomal inversions that differentiate the tomato and potato genomes. All of the inversions appear to have resulted from single breakpoints at or near the centromeres of the affected chromosomes, the result being the inversion of entire chromosome arms. While the crossing over rate among chromosomes appears to be uniformly distributed with respect to chromosome size, there is tremendous heterogeneity of crossing over within chromosomes. Regions of the map corresponding to centromeres and centromeric heterochromatin, and in some instances telomeres, experience up to 10-fold less recombination than other areas of the genome. Overall, 28% of the mapped loci reside in areas of putatively suppressed recombination. This includes loci corresponding to both random, single copy genomic clones and transcribed genes (detected with cDNA probes). The extreme heterogeneity of crossing over within chromosomes has both practical and evolutionary implications. Currently tomato and potato are among the most thoroughly mapped eukaryotic species and the availability of high density molecular linkage maps should facilitate chromosome walking, quantitative trait mapping, marker-assisted breeding and evolutionary studies in these two important and well studied crop species.
已经构建了番茄和马铃薯基因组的高密度分子连锁图谱，这些图谱由1000多个标记组成，标记之间的平均间距约为1.2厘摩（约900千碱基对）。由于这两张图谱基于一组共同的探针，因此能够高精度地确定与区分番茄和马铃薯基因组的5个染色体倒位相对应的断点。所有这些倒位似乎都是由受影响染色体着丝粒处或其附近的单个断点导致的，结果是整个染色体臂发生倒位。虽然染色体之间的交叉率似乎相对于染色体大小呈均匀分布，但染色体内部的交叉存在极大的异质性。图谱中与着丝粒和着丝粒异染色质相对应的区域，以及在某些情况下与端粒相对应的区域，其重组率比基因组的其他区域低达10倍。总体而言，28%的定位基因座位于假定重组受抑制的区域。这包括与随机单拷贝基因组克隆和转录基因（用cDNA探针检测）相对应的基因座。染色体内部交叉的极端异质性具有实际和进化意义。目前，番茄和马铃薯是绘制图谱最详尽的真核生物物种之一，高密度分子连锁图谱的可用性应有助于在这两个重要且研究充分的作物物种中进行染色体步移、数量性状定位、标记辅助育种和进化研究。
