First Coffea arabica karyogram showing that this species is a true allotetraploid

Evolutive studies have verified that Coffea arabica (2n = 44) is a natural segmental allopolyploid originated from a cross between two diploid (2n = 22) Coffea species. Data obtained by classical cytogenetic analyses showed that C. arabica chromosomes are small and morphologically similar, which hampers the karyogram assembly with well-identified homologue pairs. In the present study, the C. arabica complement was reanalysed using an improved cytogenetic protocol that allowed the obtention of high-quality prometaphasic and metaphasic chromosomes. The results showed that chromosomes are cytogenetically distinct (1, 2, 19, 20, 21 and 22) and identical (3-4, 5-6, 7-8, 9-10, 11-12, 13-14, 15-16 and 17-18), with regard to their total length, short and long arm sizes or chromosome classes. Our work suggests that C. arabica is a true non-segmental allotetraploid but originated from different species exhibiting similar and distinct chromosomes.