Characterization of Lettuce Chromosomes Based on Condensation Patterns and Physical Mapping of 45S and 5S rDNAs Using Fluorescence in situ Hybridization

摘要

Lactuca sativa L. is one of the most important reference species for genome research in Compositae. In the present study, chromosome image analysis system IV (CHIAS IV) and fluorescence in situ hybridization (FISH) were applied to obtain detailed information of the characteristics of lettuce chromosomes. One lettuce cultivar of L. sativa and three wild species of L. serriola, L. saligna and L. virosa were used to analyze chromosome lengths, arm ratios and degrees of chromosomal condensation at prometaphase. Locations of 45S and 5S rRNA genes were determined by FISH technique. Our results showed that nine pairs of homologous chromosomes could be discriminated for all four species by their morphological characteristics, condensation patterns (CPs) and localization of rRNA loci. Statistical analysis showed that the total length of L. saligna chromosomes was significantly the shortest among the species tested. The present study is the first for the physical mapping of condensed regions and rDNAs using CPs and FISH of prometaphase chromosomes in lettuce. The information provided here would be valuable for practical breeding and genetics of lettuce.