Physical location of SSR regions and cytogenetic instabilities in Pinus sylvestris chromosomes revealed by ND-FISH.

Abstract

Portugal constitutes the southwestern end limit of the distribution area of Scots pine in the world. The population of ‘Ribeira das Negras’ (‘Serra do Geres’; NW Portugal) has been considered potentially native and peripheral. This species has 24 chromosomes, hardly distinguishable because of their similar size and shape. Cytogenetic studies are scarce and instabilities were previously reported in peripheral Scots pine populations. Here, we intended to cytogenetically characterize individuals from ‘Ribeira das Negras’ using 14 simple sequence repeats (SSRs) and 45S rDNA sequence (pTa71) as probes, by nondenaturing fluorescence in situ hybridization (ND-FISH) and FISH, respectively. Eight SSRs [(AC)10; (AG)10; (AG)12; (AAG)5; (AAC)5; (GATA)4; (GACA)5 and (GGAT)4] and pTa71 showed hybridization. The (AG)10 probe hybridized on all chromosomes and an ideogram was constructed. Each metaphase cell presented cytogenetic instabilities corroborating ‘Ribeira das Negras’ as a peripheral population. As far as we know, this is the first cytogenetic study in Scots pine using SSRs in FISH experiments. Scots pine (Pinus sylvestris L.) is one of the most widely distributed conifers across Eurasia and an economically important species as source of timber (Manson and Alia 2000). Peripheral populations of Scots pine are susceptible to marginal environments and could present high phenotypic variation as well as cytogenetic irregularities (Muratova 1994). Cytogenetic studies in gymnosperms constitute a hard task due to incomplete cell division synchronization