The evolution in chili peppers (Capsicum – Solanaceae), a view from the cytogenetics

MOSCONE, E. A.; SCALDAFERRO, M. A.; GRABIELE, M.; CECCHINI, N. M.; SÁNCHEZ GARCÍA, Y.; DAVIÑA, J. R.; DUCASSE, D. A.; BARBOZA, G. E.; EHRENDOFER, F.

Madison (USA)

Congreso; PAA/Solanaceae 2006: Genomics Meets Biodiversity (VI International Solanaceae Conference); 2006

Botanical Society of America (USA)

Capsicum (chili peppers) is a New World genus of great economical importance for food and spice, with five crop species. An up-to-date summary of the karyotypic knowledge is presented, including data on classical staining, silver impregnation, fluorescent chromosome banding (chromomycin A3, distamycin A, DAPI and actinomycin D staining), nuclear DNA content measurements, and fluorescent in situ hybridization with telomeric sequence. Reported chromosome numbers for 23 of the ca. 31 recognized species allow to distinguish two species groups: one with 2n=2x=24 (13 species) and another with 2n=2x=26 (10 species). The 2n=24 species have comparatively symmetrical karyotypes, mostly with 11m+1st (sm) pairs; C. annuum and C. parvifolium also have cytotypes with 11m+1sm+1st and 12 m pairs, respectively. In contrast, the 2n=26 taxa exhibit more asymmetrical complements, with more sm (st) chromosomes and frequently one t chromosome. Active nucleolar organizing regions vary in number from one (several species) to four pairs (C. baccatum). Heterochromatin amount ranges from 1.88% (C. annuum) to 38.91% (C. tovarii) of the karyotype length, whilst 1C DNA content varies from 3.35 pg (C. chacoense) to 5.77 pg (C. parvifolium). GC-rich heterochromatin is universal in the genus, although AT-rich heterochromatin also appears in C. pubescens and C. campylopodium. Lack of telomeric sequences in ectopic localizations in the 2n=24 species supports the hypothesis that x=13 has derived from x=12. Results on chromosome differentiation are compared with molecular data and a scheme of the possible evolutionary trends in Capsicum with particular reference to the origin of the cultivated taxa is presented. Karyological analyses provide valuable diagnostic features for taxonomic identification at species level in the cultivated taxa, particularly the C. annuum complex.