Different observers introduce not negligible biases in comparative karyomorphological studies

Within a practical course of cytotaxonomy organized in Pisa (Italy) on February 2024 by the Group for Floristics, Systematics and Evolution of the Italian Botanical Society, we tested whether using image analysis softwares possible biases are still introduced by different observers. We conclude that observer bias selectively applies in possibly overestimating the length of short arms in a karyotype. As a consequence, the parameters most sensitive to these possible errors are CV_CI and CV_CL, and to a less degree M_CA and THL. To achieve more stable results among observers, a still lacking standardized measurement protocol could be helpful.