A molecular cytogenetic analysis of chromosome behavior in Lilium ...

Chapter 5Fig. 5.1. Discovery of B chromosomes in the male parent (LLTT) and its multicolour GISH analysisin the progeny. (a) Two Bs in the male (L) parent of the tetraploid LLTT (white arrows). (b) Bchromosome (white arrow) was blocked by L genome DNA in multicolour GISH in genotype 076928-21 (LLO × LLTT) in which GISH clearly identified the chromosomes of the three genomes. T= red(biotin labelled and detected with Cy3– streptavidin); O= green (digoxigenin labelled and detectedwith anti-digoxigenin FITC system) and L= blue (DAPI counterstaining)ResultsExtra chromosomes in progenies of LLO × LLTTAs a first step, the karyotypes of the two parents were investigated for their chromosomeconstitution. Whereas the triploid LLO possessed the expected 36 chromosomes without anyextra chromosomes, there were two small extra chromosomes in the LLTT parent in additionto the normal chromosome complement (Fig. 5.1a). As expected, all the progenies from LLO× LLTT combination were aneuploid with chromosome number varying from 39 to 45.Beside the standard chromosomes (As), the small extra chromosomes were also detected inthe progeny. Besides their small size, the extra chromosomes were clearly metacentric andpresent in all somatic metaphase cells of the root meristem. Because chromosomes of threedifferent genomes (i.e., L, T and O) were expected to be present in the progenies of the LLO× LLTT cross, multicolour GISH analysis was used to analyze these progenies. Resultsshowed that chromosomes of the three genomes could be clearly distinguished and there wasindication that the small extra chromosome was blocked by Longiflorum DNA (Fig. 5.1b).Out of the analyzed 26 offspring plants, 19 genotypes possessed either one or two extrachromosomes, which will be mentioned as B chromosomes (Bs), whereas seven of the 26progenies had no Bs (Table 5.1). This indicated that the transmission of Bs through the maleparent LLTT was very high (73.4 %).64