Microsatellites or simple sequence repeats (SSRs) are highly polymorphic, codominant markers that have great value for the construction of genetic maps, comparative mapping, population genetic surveys, and paternity analyses. Here, we report the development and testing of a set of SSR markers derived from shotgun sequencing from Populus trichocarpa Torr. & A. Gray, a nonenriched genomic DNA library, and bacterial artificial chromosomes. Approximately 23% of the 1536 genomic clones and 48% of the 768 bacterial artificial chromosome subclones contained an SSR. Of the sequences containing an SSR, 72.4% contained a dinucleotide, 19.5% a trinucleotide, and 8.1% a tetranucleotide repeat unit; 26.6% of the sequences contained multiple SSR motifs in a complex or compound repeat structures. A survey of the genome sequence database revealed very similar proportional distribution, indicating that our limited rapid, shallow sequencing effort is representative of genome-wide patterns. In total, 492 primer pairs were designed and these yielded 77 markers that were mapped in an F2 pedigree, including 26 that were sufficiently informative to be included in a Populus framework map. SSRs with GC-rich motifs mapped at a significantly higher frequency than expected, although AT-rich SSRs accounted for the majority of mapped markers due to their higher representation in the genome. SSR markers developed from P. trichocarpa showed high utility throughout the genus, with amplification rates in excess of 70% for all Populus species tested. Finally, at least 30% of the markers amplified in several willow species, suggesting that some of these SSRs will be transferable across genera.

利用300个随机的寡核苷酸引物和马尾松（Pinus massoniana Lamb.）种子的胚乳（大配子体）产生的随机扩增多态性DNA（RAPD）分子标记，进行马尾松标记连锁图谱的构建。经筛选共获得64个稳定的RAPD标记，利用多点连锁分析，其中的48个标记分属于13个不同的连锁群（连锁对），该图谱覆盖的基因组总长度约为692.5cM（centimorgan），标记问平均距离约为14.7cM，它为马尾松连锁图谱的构建提供了一个连锁框架。

构建遗传图谱是当前生物学研究领域中的一个热点，进行图谱构建，林木与作物既有共性。又有各自的特点。因为进行图谱构建一是要有合适的分离群体，二是要有能揭示亲本多态性的遗传标记。两者可利用的遗传标记是一样的，但在进行作图群体构建时却存在一定差异，林木的遗传组成高度杂合，大多数林木为长期异交的树种，一般都有自交不亲合和近交衰退现象，象作物那样利用近交系或其它的高世代群体进行遗传图谱构建是不太可能的。由于研究方法的不同，以前的林木育种工作者很少留意建立和保存谱系清楚的F2和BCl群体，由于林木生命周期很长，建立这样一些高世代的群体也需要很长的时间，而且除了杨树、柳树等一些可在温室内水培杂交的物种，大多数林木的控制授粉杂交操作也是很困难的。因此研究过程中，等待材料的问题成为目前林木遗传图谱构建的主要限制因子之一。如何利用现成的材料和低世代群体，对林木遗传图谱构建工作的广泛开展具有重要意义。下面就这一问题作一些理论上的探讨和分析。

本文简要介绍了90年代以来利用RFLP和RAPD分子标记构建林木的遗传连锁图谱，并应用高密度的遗传连锁图谱上的分子标记进行林木重要数量性状的QTL作图，进而阐明控制多基因的数目，确定QTL在染色体上的位置，测定单个基因的作用效应。遗传连锁图谱构建和数量性状基因定位预示林木遗传育种研究将产生深刻的变革。

The appraisal of cultivar authenticity is a problem that needs to be settled in agricultural and forestry activities. AFLP is a novel, reliable and effective technique in DNA fingerprint. 42 clones of Populus deltoides Mash. were fingerprinted with the technique. AFLP technique can be widely used in the practical cultivar identification.