Heterochromatin type, amount and distribution in wild species of chili peppers (Capsicum, Solanaceae)

Triple staining with the fluorochromes chromomycin A3, distamycin A and 4′-6-diamidino-2-phenylindole (CMA/DA/DAPI) was applied to somatic metaphases and interphase nuclei of 11 taxa of wild chili peppers ( Capsicum ), with 2 n = 2 x = 24 ( C. annuum var. glabriusculum , C. cardenasii , C. chacoense , C. flexuosum , C. galapagoense , C. eximium , C. praetermissum and C. tovarii ) and 2 n = 2 x = 26 ( C. recurvatum , C. rhomboideum and C. villosum ) to analyse heterochromatin type, amount and distribution in wild members of this genus. Heterochromatic banding patterns allowed the identification of all the taxa examined and contributed to their taxonomic grouping. GC-rich heterochromatin (CMA+/DAPI−) was typical in all taxa; only C. praetermissum possessed also AT-rich (CMA−/DAPI+) and mixed GC- and AT-rich (CMA+/DAPI+) bands. Heterochromatin amount (expressed as % of karyotype length) ranged between 1.72 ( C. chacoense ) and 16.82 ( C. flexuosum ) and was positively correlated with karyotype length in most of the taxa examined. Heterochromatin located mainly at terminal position of chromosomes but intercalary position prevailed in C. flexuosum . Nucleolus organizer regions (NOR)-associated GC-rich heterochromatin was exclusively terminal and included the distal macrosatellite and a small portion on the corresponding arm. In all the taxa analysed, an equilocal heterochromatin distribution in non-homologous chromosomes of karyotype was observed, suggesting concerted evolution of heterochromatin dispersion in Capsicum .