Fossati T, Grassi F, Sala F, Castiglione S
Department of Biology, University of Milan, Via Celoria 26-20133 Milan, Italy.
Mol Ecol. 2003 Aug;12(8):2033-43. doi: 10.1046/j.1365-294x.2003.01885.x.
In this study six simple sequence repeats (SSR or microsatellites) were selected for their ability to fingerprint a total of 60 commercial clones of Populus deltoides Marsh. and Populus x canadensis Moench (typically derived from crosses between Populus nigra L and P. deltoides) and to characterize a natural population of P. nigra growing along the Ticino river in the North of Italy. Out of six SSRs used, four microsatellite loci were found to have alleles which were species-specific to P. deltoides and could therefore be used as markers for introgression of P. deltoides into P. nigra. In the studied region hybrid poplars and P. deltoides commercial clones are cultivated as monoclonal stands close to the area where black poplar has its natural habitat. SSR analysis was performed to investigate whether there was evidence of introgression between the natural population and the monoclonal plantations of hybrids and P. deltoides clones cultivated in the surrounding area. Three stages of the natural population were analysed: a group of old trees about a hundred years old, a younger population (aged 2-30 years) and the seedlings of three females of this population. Alleles specific to P. deltoides were detected only in the old cohort of the natural population, while no introgression was observed in the younger individuals and their progenies. These results were also confirmed by isozyme analysis of loci PGI-B, PGM and LAP-A, which were previously identified as diagnostic for P. nigra, P. deltoides and P.xcanadensis.
在本研究中，选择了六个简单序列重复（SSR或微卫星），因其能够对总共60个美洲黑杨（Populus deltoides Marsh.）和加杨（Populus x canadensis Moench，通常源自黑杨（Populus nigra L）与美洲黑杨的杂交）的商业无性系进行指纹识别，并对生长在意大利北部提契诺河沿岸的黑杨天然种群进行特征描述。在所使用的六个SSR中，发现四个微卫星位点具有美洲黑杨特有的等位基因，因此可作为美洲黑杨渗入黑杨中的标记。在研究区域，杂交杨树和美洲黑杨商业无性系作为单克隆林分种植在黑杨自然栖息地附近。进行SSR分析以调查在天然种群与周围地区种植的杂交种和美洲黑杨无性系单克隆人工林之间是否存在渗入证据。对天然种群的三个阶段进行了分析：一组约一百年树龄的老树、一个较年轻种群（年龄在2至30岁之间）以及该种群中三株雌树的幼苗。仅在天然种群的老龄群体中检测到美洲黑杨特有的等位基因，而在较年轻个体及其后代中未观察到渗入现象。这些结果也通过对PGI-B、PGM和LAP-A位点的同工酶分析得到证实，这些位点先前被确定为黑杨、美洲黑杨和加杨的诊断位点。
