Psidium cattleyanum Sabine (Myrtaceae), a neotropical polyploid complex with wide geographic distribution: insights from cytogenetic and DNA content analysis

Polyploidy is a ubiquitous process in angiosperms, arising from autopolyploidy or allopolyploidy. However, few natural polyploid complexes in tropical regions have been well described. Psidium cattleyanum Sabine (Myrtaceae) is a neotropical fruit species with wide distribution and several ploidy levels reported in the literature, being characterized as a polyploid complex. In this study, we provide cytogenetic data of P. cattleyanum based on conventional (chromosome numbers, distribution, and location of CMA/DAPI bands) and molecular techniques (distribution and location of rDNA sites) and flow cytometry (genome size). Moreover, we analyzed the geographic distribution of P. cattleyanum cytotypes. For 75 individuals analyzed in this study, chromosome counts showed nine cytotypes (2n = 3x = 33 to 12x = 132), with two new records (2n = 3x = 33 and 9x = 99). Our results support the occurrence of a polyploid series in P. cattleyanum, derived by the basic number x = 11. We performed CMA/DAPI banding and FISH technique for eight and six cytotypes, respectively. The number of chromosomes, CMA/DAPI bands and 18S and 5S rDNA sites, and DNA content increased linearly related to ploidy level, suggesting the multiplication of the same genome (x = 11) in the different cytotypes. The exception to this gradual increase in DNA content was observed in the cytotypes 2n = 110 and 132, in which the values were relatively lower than expected. There was weak relation between the ploidy and latitudinal distribution. Therefore, Psidium cattleyanum is a good group to study the role of polyploidization events in the evolutionary processes of natural populations, due to the diversity of chromosome numbers and environmental conditions in which cytotypes occur.

Automated summary

This study provides cytogenetic data on Psidium cattleyanum and identifies nine cytotypes, including two new records. The chromosome counts, CMA/DAPI bands, and rDNA sites increased linearly with ploidy level, indicating the multiplication of the same genome. However, the cytotypes 2n = 110 and 132 showed lower DNA content than expected. There was a weak relationship between ploidy and latitudinal distribution.