Abstract
Identification of the potato chromosomes 1 (the longest one), 2 (the carrier of the nucleolar organizer, NOR) and 12 (the shortest one) is possible at mitosis using a combined Feulgen-haematoxylin staining or a Giemsa C-banding technique. In two aneuploids containing 27 chromosomes, three specimens of chromosome 1 were found through conventional staining. Variation of the length of the NORs and the size of the satellite of homologues or homoeologues of chromosome 2 was observed in various cytotypes. Pachytene analysis identified trisomics of chromosome 2 of interspecific origin, involving S. tuberosum L. ssp. tuberosum Hawkes and S. phureja Juz. et Buk., but only two specimens of chromosome 2 could be identified using the Giemsa C-banding technique. However, in six different interspecific chromosome 2-trisomics, three chromosomes per cell were found to show a hybridization signal by non-radioactive in situ hybridization with heterologous rDNA from pea. The high polymorphism of chromosomes observed after Giemsa C-banding made it impossible to bring the identity of the mitotic chromosomes in accordance with the results from pachytene identification in cells containing one triplicate chromosome.
