Caracterização genética de variedades morfológicas de Cereus peruvianus Mill. utilizando marcadores microssatélites

• Autor(a) principal: Neves, Andréa Florindo das
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/358
• topic: Cereus peruvianus Mill - Genética; Marcadores microssatélites; Ciências Biológicas; Biologia Geral

Cacti are plants with great adaptability in drought-stricken regions and with high ecological and economical relevance. The stems different morphologies, as well as flowers and fruits, are employed to classify the family´s genera and species. The species Cereus peruvianus, popularly known as mandacaru, may be found throughout Brazil. It is used as an ornamental plant, for industrial purposes and is the main forage plant in the rainless region of the northeastern region of Brazil. Whereas monstrous varieties of the species may be found with their stem forming ribs with irregular ridges and a variable number of areoles per rib, there is the crooked variety with spiral-form ribs. It is not adequate to classify cacti merely by their morphology since there high plasticity rates are extant in their morphological characteristics. Current investigation employs heterologous microsatellite markers to determine the variability and genetic relationship among plant populations with crooked (morphotype 2) and monstrous (morphotype 3) phenotypes when compared to populations of C. peruvianus (morphotype 1). Thirty-three primer pairs were developed for different cactus species for the selection of microsatellite markers. Twelve pairs of microsatellites primers developed for Polaskia chichipe, Ariocarpus bravoanus, Astrophytum asterias and Echinocactus grusonii were then selected with 36.36% transferability for C. peruvianus. Seven out of the twelve primers were polymorphic and employed to analyze genetic diversity. The analysis of the seven microsatellite loci in the samples of the three mandacaru morphotypes provided the amplification of 17 alleles with mean 2.43 alleles per polymorphic locus and mean polymorphisms of 90.47%. Variable frequencies of alleles A, B or C in the seven SSR loci provided heterozygosity ranging between 0.00 and 0.7368 and an expected heterozygosity between 0.00 and 0.6771. Fis mean rate for the seven loci was 0.1821 and showed that there was an excess in homozygotes, whereas analysis of genetic divergence among the three sample groups was shown to be moderate (Fst=0.0962). The analysis of molecular variance (AMOVA) revealed that the highest variance was found within populations of each morphotype with FST and RST rates equal to 87% and 85% respectively. Variability rates among populations went to FST=13% and RST=15%, highly significant rates (p<0.0001). Similarity among samples varied between 0.8456 and 0.9329. Dendrogram showed the formation of two groups. One was formed by morphotypes 1 and 2 and showed that the highest similarity occurred between Cereus peruvianus plants with normal morphology and the tortuosus variety. Morphotype 3 (var. monstruosus) remained segregated from the others and showed the greatest divergence. Genetic relationships among individual genotypes were also assessed by the Bayesian analysis; ΔK rate, which should be taken into consideration to define the number of groups, indicated the formation of three groups, or rather, the number of formed groupings was maintained by the UPGMA grouping method. While confirming the non-specification of alleles associated with morphology, the bar plot revealed that the three morphotypes shared alleles with the seven microsatellites under analysis. The largest genetic differentiation at the molecular level (speciation) found among the plants of the C. peruvianus var. tortuosus and C. peruvianus var. monstruosus varieties are being targeted by a rigid process of artificial selection, since these two varieties exhibit a marked ornamental character.