ABSTRACT The reproductive system of flowering plants can be highly variable, affecting their biology, gene flow and genetic variability among populations. Petunia secreta is a rare annual endemic species of Pedra do Segredo, located in the municipality of Caçapava do Sul, state of Rio Grande do Sul, Brazil. Although rare, the species possesses a high level of genetic variability. We investigated the reproductive system of P. secreta, including fruit production and seed germinability, in order to determine if its reproductive system can explain its genetic diversity. We sampled five populations and conducted five greenhouse hand-pollination treatments: 1) autonomous apomixis; 2) self-pollination; 3) hand self-pollination; 4) geitonogamy; and 5) cross-pollination. We analysed a total of 40 plants, 468 flowers, and 6,500 seeds. Only autonomous apomixis and self-pollination did not produce fruit. No differences in fruit weight were observed among pollination treatments (P > 0.05). Seeds of two colours were produced, with no differences in germinability. Considering all plants, populations, and treatments, the average germinability was 73 % (range 9 % to 100 %). These results, along with other previous studies, indicate that the reproductive systems of P. secreta, and its large effective population size, can explain its high genetic diversity.
Abstract Sisyrinchium is the largest genus of Iridaceae in the Americas and has the greatest amount of cytological data available. This study aimed at investigating how genomes evolved in this genus. Chromosome number, genome size and altitude from species of sect. Viperella were analyzed in a phylogenetic context. Meiotic and pollen analyses were performed to assess reproductive success of natural populations, especially from those polyploid taxa. Character optimizations revealed that the common ancestor of sect. Viperella was probably diploid (2n = 2x =18) with two subsequent polyplodization events. Total DNA content (2C) varied considerably across the phylogeny with larger genomes detected mainly in polyploid species. Altitude also varied across the phylogeny, however no significant relationship was found between DNA content changes and altitude in our data set. All taxa presented regular meiosis and pollen viability (> 87%), except for S. sp. nov. aff. alatum (22.70%), suggesting a recent hybrid origin. Chromosome number is mostly constant within this section and polyploidy is the only source of modification. Although 2C varied considerably among the 20 taxa investigated, the diversity observed cannot be attributed only to polyploidy events because large variations of DNA content were also observed among diploids.
The population of Argentina has already been studied with regard to several genetic markers, but much more data are needed for the appropriate definition of its genetic profile. This study aimed at investigating the admixture patterns and genetic structure in Central Argentina, using biparental markers and comparing the results with those previously obtained by us with mitochondrial DNA (mtDNA) in the same samples. A total of 521 healthy unrelated individuals living in 13 villages of the Córdoba and San Luis provinces were tested. The individuals were genotyped for ten autosomal ancestry informative markers (AIMs). Allele frequencies were compared with those of African, European and Native American populations, chosen to represent parental contributions. The AIM estimates indicated a greater influence of the Native American ancestry as compared to previous studies in the same or other Argentinean regions, but smaller than that observed with the mtDNA tests. These differences can be explained, respectively, by different genetic contributions between rural and urban areas, and asymmetric gene flow occurred in the past. But a most unexpected finding was the marked interpopulation genetic homogeneity found in villages located in diverse geographic environments across a wide territory, suggesting considerable gene flow.
The Metabolic Syndrome (MetS) is defined as a pattern of metabolic disturbances, which include central obesity, insulin resistance and hyperglycemia, dyslipidemia, and hypertension. Milk has been promoted as a healthy beverage that can improve the management of MetS. Most human adults, however, down-regulate the production of intestinal lactase after weaning. Lactase encoded by the LCT gene is necessary for lactose digestion. The -13910C > T SNP (rs4988235) is responsible for the lactase persistence phenotype in European populations. We herein investigated whether the lactase persistence genotype is also associated with the MetS in subjects from a Brazilian population of European descent. This study consisted of 334 individuals (average age of 41 years) genotyped by PCR-based methods for the -13910C > T SNP. Clinical data were assessed and the genotypes were tested for their independent contribution to the MetS using chi-square tests and multiple logistic regression analysis. Univariate analyses showed that hypertension and MetS prevalence were higher in individuals with the lactase non-persistence genotype than in lactase persistence subjects. Furthermore, lactase persistence was associated with a lower risk for MetS (OR = 0.467; 95% CI 0.264-0.824; p = 0.009). These results suggest that LCT genotypes can be a valuable tool for the management of MetS treatment.
Alpha thalassemia has not been systematically investigated in Brazil. In this study, 493 unrelated individuals from the southernmost Brazilian state of Rio Grande do Sul were screened for deletional forms of α-thalassemia. One hundred and one individuals had microcytic anemia (MCV < 80 fL) and a normal hemoglobin pattern (Hb A2 < 3.5% and Hb F < 1%). The subjects were screened for -α3.7,-α4.2,-α20.5, -SEA and -MED deletions but only the -α3.7 allele was detected. The -α3.7 allele frequency in Brazilians of European and African ancestry was 0.02 and 0.12, respectively, whereas in individuals with microcytosis the frequency was 0.20. The prevalence of α-thalassemia was significantly higher in individuals with microcytosis than in healthy individuals (p = 0.001), regardless of their ethnic origin. There were also significant differences in the hematological parameters of individuals with -α3.7/αα, -α3.7/α3.7 and β-thalassemia trait compared to healthy subjects. These data suggest that α-thalassemia is an important cause of microcytosis and mild anemia in Brazilians.
The green aphid Schizaphis graminum (Rondani) is an important pest of Graminae. Samples of this aphid were collected at three environmentally distinct Brazilian localities, Passo Fundo (RS), Jaguariuna (SP) and Dourados (MS). Alatae and apterous viviparous forms were reared on the BR-35 wheat (Triticum aestivum) strain under controlled laboratory conditions and studied as to their variability in measures of body size and production of progeny. Univariate (ANOVA) and multivariate (canonical discriminant functions) techniques were used to evaluate differences among the three populations. Conspicuous differences between populations were observed in the length of five structures of the alatae and eight of the apterous forms, as well as in offspring production. The greatest dispersion in the length of general structures of the individuals obtained by the canonical discriminant function was for Passo Fundo, where climatic conditions are more severe and where aphids cause the most serious damage to wheat crop.
O afídeo verde Schizaphis graminum (Rondani) é uma praga importante em gramíneas. Amostras deste afídeo foram coletadas em três localidades brasileiras caracterizadas por diferentes condições ambientais, Passo Fundo (RS), Jaguariuna (SP) e Dourados (MS).Formas vivíparas aladas e ápteras foram criadas na linhagem de trigo (Triticum aestivum) BR-35 sob condições controladas em laboratório e estudadas e quanto à sua variabilidade em medidas do tamanho do corpo e produção de descendência. Técnicas univariadas (ANOVA) e multivariadas (funções discriminantes canônicas) foram usadas para avaliar diferenças entre as tres populações. Diferenças conspícuas entre populações foram observadas no comprimento de cinco estruturas das formas aladas e oito das ápteras, bem como na produção de descendência. A maior dispersão no comprimento de estruturas dos indivíduos em geral, obtida pela função discriminante canônica foi para a população de Passo Fundo, onde as condições climáticas são mais severas e onde os afídeos causam dano mais sério à cultura de trigo.
Summary The Ticuna Indians of Brazil are now a largely acculturated and integrated tribe situated for the most part in villages along the Solimões river. Demographic information collected in eight of their villages is reported here. For five of them detailed data concerning migration, fertility and mortality were obtained. The are characterized by a relatively large mobility, high fertility (moan number of livebirths per female of age 40 or more : seven), low (2.5%) frequency of sterile couples, and relatively low mortality for groups living at this cultural stage (25% of deaths before the age of reproduction). This low mortality, and a relatively small variance in the number of liveborn children in completed families, lead to the lowest index of opportunity for selection obtained thus far in populations of South American Indians (0,54).
Resumo Os índios Ticuna do Brasil são atualmente uma tribo bastante aculturada e integrada, que habita, na sua maioria, aldeias localizadas ao longo do rio Solimões. São aqui apresentados dados demográficos coletados em oito destas aldeias, sendo que para cinco delas foram obtidas informações minuciosas quanto à migração, fertilidade e mortalidade. Os Ticuna caracterizam-se por uma mobilidade relativamente grande, fertililidade alta (número médio de filhos nascidos vivos por mulher com > 40 anos :7), baixa freqüência de casais estéreis (2,5%) e uma mortalidade relativamente pequena para grupos que vivem neste estágio cultural (25% de mortes antes da idade de reprodução). A mortalidade baixa e uma variância também pequena no número de nascidos vivos em irmandades completas levaram a um índice de oportunidade para seleção igual a 0.54 o menor obtido até agora em populações de índios sul-americanos.