Pilosocereus Pernambucoensis F.ritter (cactaceae - cactoideae): etnobotânica, citogenética, evolução cariotípica

Abstract

Cactaceae are plants perfectly adapted to arid and semi-arid environments with exclusive distribution in the American continent. Initially, a literature review was conducted, addressing ethnobotanical uses, systematic and numerical chromosomal variation in the Cactaceae family, particularly in the genus Pilosocereus, with special emphasis on P. pernambucoensis. Historical aspects of ethnobotany and cytogenetics, as well as uses and potentials for secondary metabolite production, were also included. Cactaceae have extensive ethnobotanical use in the American continent, especially by populations in arid and semi-arid environments, serving as food resources, timber, medicinal plants, fodder, and ornamental plants, among others. The family comprises 94 genera and 1,150 species, divided into four subfamilies: Pereskioideae, Opuntioideae, Cactoideae, and Maihuenioideae. Pilosocereus has a wide distribution in the American continent, consisting of 42 species, 29 of which occur in Brazil. For the genus, chromosomal records of 2n = 22 are known in most species, 2n = 44 for four species, and 2n = 88 for a single population of P. gounellei. For Pilosocereus pernambucoensis, there are records of 2n = 44 for several populations in Paraíba, Pernambuco, and Alagoas, and 2n = 22 for a single population in Pernambuco. This species faces taxonomic delimitation issues, with at least three names involved within its boundaries. The genus is frequently found in the northeastern semi-arid region, with several species used by rural communities, primarily as fodder supplements during prolonged droughts. Pilosocereus pachycladus, a species morphologically related to P. pernambucoensis, has a broad distribution in the Northeast Region, with some areas of sympatry and the occurrence of intermediate forms. We analyzed various populations of P. pernambucoensis using conventional staining with Giemsa and the fluorochromes CMA (Chromomycin A3) and DAPI (4′,6-diamidino-2- phenylindole) to document the occurrence of numerical chromosomal variations. All populations of P. pernambucoensis were tetraploid with 2n = 44 and exhibited identical banding patterns among themselves and with the supposedly related species, P. pachycladus. Despite the occurrence of polyploidy in all analyzed populations of P. pernambucoensis and P. pachycladus, other semi-domesticated species are diploid, and there seems to be no correlation between polyploidy incidence in these species and the domestication process. Counting a morphologically similar species to P. pernambucoensis with 2n = 22 in Pernambuco, geographically close to where a supposed diploid population of P. pernambucoensis was collected, raises questions about this previous record, which might have been the result of a possible identification error.