A critical assessment of karyotype analysis by imaging methods

A critical evaluation of the digital data of 250 barley metaphase spreads obtained by image analysis revealed the instability of the chromosomal morphology during the mitotic metaphase stage. Both the relative length (RL) and arm ratio (AR) of the chromosomes, which are the two major numerical parameters in karyotype analysis, varied in the different chromosomal spreads. The ranking of the chromosomes for the respective parameters within a complement changed accordingly. The data indicated that karyotype analysis based merely on the numerical parameters RL and AR may lead to the misidentification of chromosomes, causing a misinterpretation of the data from different chromosomes when averaging several data. Thus, most of data of the RL and AR which have so far been reported may need reexamination except for the cases where chromosomes were identified based oh other critical parameters, e.g., banding pattern, condensation pattern, in situ hybridization, etc. Differential condensation between the chromosome arms may be the cause of the instability of the karyotype.