Cytology and DNA content variation of Capsicum genomes

Abstract

Chromosome data and characterization by fluorescent banding, silver nucleolar organizer region staining (AgNOR), and fluorescence in situ hybridization (FISH) are compiled in this chapter, together with estimations of nuclear DNA content of Capsicum species. To date, the diploid chromosome number of 77.8% of the species in the genus has been recorded. The chromosome number distinguishes two groups of species, one with 2n=2x= 24 and the other with 2n=2x= 26. Only two clades, Andean and Atlantic Forest, possess the chromosome number of 2n= 26.A physical chromosome map with heterochromatin distribution besides5Sand active and inactive 45S ribosomal genes (rDNA) of 12 Capsicum taxa was constructed using fluorescent banding, AgNOR and FISH. The chromosome banding pattern with fluorochromes chromomycin A3 and 4′-6-diamidino-2-phenylindole (CMA/DAPI) reveals number of bands, distribution and content of heterochromatin, and FISH reports the localization of 5Sand active and inactive 45S rDNA. Both methods are specific and, together with morphological characters, are instrumental for identifying taxa in Capsicum. AgNOR method informs the number, size, and position of just active NORs. Additionally, nuclear DNA content was estimated for nine diploid species of Capsicum by flow cytometry. Genome size displays significant variation between but not within species and contributes to their taxonomic grouping.