Similaridade cariotípica e afinidade genômica entre três espécies de Piper L. nativas da Amazônia

Abstract

The Piperaceae family is known to be a producer of essential oils as part of its secondary metabolism. The genus Piper has 1400 species, of which 400 occur in Brazil. The native species of Acre: P. aduncum, P. hispidinervum and P. affinis hispidinervum, respectively, are producers of dilapiol, safrol and sarisan, oils of economic importance because they have bioinsecticidal activity, besides use in the chemical and perfumery industries. The species are morphologically similar, which generates great taxonomic controversy. Some studies classify P. aduncum and P. hispidinervum as distinct species, others consider P. hispidinervum as a chemotype of P. aduncum. The classification of P. affinis hispidinervumis also discussed, being classified as a chemotype of P. hispidinervum, or a hybrid between P. hispidinervum and P. aduncum. The taxonomic definition lacks information with higher resolution and the study of the chromosomes can help in distinguishing the species.In the present work, the native species of Acre were evaluated: P. aduncum, P. hispidinervum and P. affinis hispidinervum, for their karyotype, fluorescent banding pattern, 45S and 5S ribosomal DNA (rDNA) by fluorescence in situ hybridization and genomic affinity analysis by means of genomic in situ hybridization, in order to identify chromosomal polymorphisms, which may contribute to their differentiation. The three species have 2n = 26, x = 13. Piper aduncum presented chromosomes ranging from 1.41 to 3.32 μm, P. hispidinervum from 1.65 to 3.70 μm and P. affinis hispidinervum from 1.60 to 4.22 μm. The morphology ofP. aduncum chromosomes was metacentric and that of P. hispidinervum and P. affinis hispidinervum was composed of metacentric and submetacentric chromosomes. The three species have a genome with size close to 1.00 pg. All presented a proximal CMA+ band on a pair of homologous chromosomes. Binding with the fluorochrome DAPI did not produce bands. rDNA analysis identified a pair of proximal heteromorphic 45S signals on chromosome 4, which co-located the CMA+ bands, and a pair of proximal 5S signals on chromosome 7 in all three species. Genomic affinity through reciprocal hybridizations involving the three species revealed very similar patterns, predominantly pericentromeric and proximal signals on all chromosomes in all species, revealing the similarity of the repetitive fraction regarding type and localization. Therfore, from a karyotypic point of view, the taxa P. aduncum, P. hispidinervum and P. affinis hispidinervum are very similar, with no clear separation among them.