RESUMO
Calculating epidemiological measures of infection by Trypanosoma cruzi, the causative agent of Chagas disease, is complex, because it involves several species, different stages of infection in humans and multiple transmission routes. Using the next-generation matrix method, we analysed a model which considers the three stages of human infection, triatomines and dogs (the main domestic reservoirs of T. cruzi when triatomines are present) and the main transmission routes. We derived R 0 and type-reproduction numbers T. We deduced formulas for the number of new infections generated through each transmission route by each infected individual. We applied our findings in Argentine Gran Chaco. The expressions achieved allowed quantifying the high infectivity of dogs and emphasizing the epidemiological importance of the long and asymptomatic chronic indeterminate stage in humans in the spread of the infection. According to the model, it is expected that one infected human infects 21 triatomines, that 100 infected triatomines are necessary to infect one human and 34 to infect a dog, and that each dog infects on average one triatomine per day. Our results may allow quantifying the effect of control measures on infected humans, triatomines and dogs (or other highly infected vertebrate) or on a specific route of transmission, in other scenarios.
Assuntos
Doença de Chagas/transmissão , Doenças do Cão/transmissão , Insetos Vetores/parasitologia , Triatominae/parasitologia , Trypanosoma cruzi/fisiologia , Animais , Argentina/epidemiologia , Doença de Chagas/epidemiologia , Reservatórios de Doenças , Doenças do Cão/epidemiologia , Doenças do Cão/parasitologia , Cães , Doenças Endêmicas , Humanos , Modelos Biológicos , Modelos Teóricos , População RuralRESUMO
Arbuscular mycorrhizal fungi (AMF) colonize land plants in every ecosystem, even extreme conditions such as saline soils. In the present work we report for the first time the mycorrhizal status and the vertical fungal distribution of AMF spores present in the rhizospheric soil samples of four species of Chenopodiaceae (Allenrolfea patagonica, Atriplex argentina, Heterostachys ritteriana and Suaeda divaricata) at five different depths in two saline of central Argentina. Roots showed medium, low or no colonization (0-50%). Nineteen morphologically distinctive AMF species were recovered. The number of AMF spores ranged between 3 and 1162 per 100 g dry soil, and AMF spore number decreased as depth increased at both sites. The highest spore number was recorded in the upper soil depth (0-10 cm) and in S. divaricata. Depending of the host plant, some AMF species sporulated mainly in the deep soil layers (Glomus magnicaule in Allenrolfea patagonica, Septoglomus aff. constrictum in Atriplex argentina), others mainly in the top layers (G. brohultti in Atriplex argentina and Septoglomus aff. constrictum in Allenrolfea patagonica). Although the low percentages of colonization or lack of it, our results show a moderate diversity of AMF associated to the species of Chenopodiaceae investigated in this study. The taxonomical diversity reveals that AMF are adapted to extreme environmental conditions from saline soils of central Argentina.
Assuntos
Biota , Micorrizas/isolamento & purificação , Cloreto de Sódio/análise , Microbiologia do Solo , Solo/química , Argentina , Contagem de Colônia Microbiana , Microscopia , Micorrizas/classificação , Micorrizas/citologia , Raízes de Plantas/microbiologia , Esporos Fúngicos/isolamento & purificaçãoRESUMO
Arbuscular mycorrhizal fungi (AMF) colonize land plants in every ecosystem, even extreme conditions such as saline soils. In the present work we report for the first time the mycorrhizal status and the vertical fungal distribution of AMF spores present in the rhizospheric soil samples of four species of Chenopodiaceae (Allenrolfea patagonica, Atriplex argentina, Heterostachys ritteriana and Suaeda divaricata) at five different depths in two saline of central Argentina. Roots showed medium, low or no colonization (0-50%). Nineteen morphologically distinctive AMF species were recovered. The number of AMF spores ranged between 3 and 1162 per 100 g dry soil, and AMF spore number decreased as depth increased at both sites. The highest spore number was recorded in the upper soil depth (0-10 cm) and in S. divaricata. Depending of the host plant, some AMF species sporulated mainly in the deep soil layers (Glomus magnicaule in Allenrolfea patagonica, Septoglomus aff. constrictum in Atriplex argentina), others mainly in the top layers (G. brohultti in Atriplex argentina and Septoglomus aff. constrictum in Allenrolfea patagonica). Although the low percentages of colonization or lack of it, our results show a moderate diversity of AMF associated to the species of Chenopodiaceae investigated in this study. The taxonomical diversity reveals that AMF are adapted to extreme environmental conditions from saline soils of central Argentina.
Assuntos
Biota , Micorrizas/isolamento & purificação , Microbiologia do Solo , Cloreto de Sódio/análise , Solo/química , Argentina , Contagem de Colônia Microbiana , Microscopia , Micorrizas/classificação , Micorrizas/citologia , Raízes de Plantas/microbiologia , Esporos Fúngicos/isolamento & purificaçãoRESUMO
Arbuscular mycorrhizal fungi (AMF) colonize land plants in every ecosystem, even extreme conditions such as saline soils. In the present work we report for the first time the mycorrhizal status and the vertical fungal distribution of AMF spores present in the rhizospheric soil samples of four species of Chenopodiaceae (Allenrolfea patagonica, Atriplex argentina, Heterostachys ritteriana and Suaeda divaricata) at five different depths in two saline of central Argentina. Roots showed medium, low or no colonization (0-50%). Nineteen morphologically distinctive AMF species were recovered. The number of AMF spores ranged between 3 and 1162 per 100 g dry soil, and AMF spore number decreased as depth increased at both sites. The highest spore number was recorded in the upper soil depth (0-10 cm) and in S. divaricata. Depending of the host plant, some AMF species sporulated mainly in the deep soil layers (Glomus magnicaule in Allenrolfea patagonica, Septoglomus aff. constrictum in Atriplex argentina), others mainly in the top layers (G. brohultti in Atriplex argentina and Septoglomus aff. constrictum in Allenrolfea patagonica). Although the low percentages of colonization or lack of it, our results show a moderate diversity of AMF associated to the species of Chenopodiaceae investigated in this study. The taxonomical diversity reveals that AMF are adapted to extreme environmental conditions from saline soils of central Argentina.
Assuntos
Biota , Micorrizas/isolamento & purificação , Microbiologia do Solo , Cloreto de Sódio/análise , Solo/química , Argentina , Contagem de Colônia Microbiana , Microscopia , Micorrizas/classificação , Micorrizas/citologia , Raízes de Plantas/microbiologia , Esporos Fúngicos/isolamento & purificaçãoRESUMO
The arbuscular mycorrhizal fungal (AMF) communities from the Yungas forests of Argentina were studied. The AMF species present in the rhizosphere of some dominant native plants (one tree: Alnus acuminata; three herbaceous species: Duchesnea indica, Oxalis conorrhiza, Trifolium aff. repens; and one shrub: Sambucus peruviana) from two sites (Quebrada del Portugués and Narváez Range) of the Yungas forests were isolated, identified and quantified during the four seasons of the year. Twenty-two AMF morphotaxa were found. Spore density of some AMF species at each site varied among seasons. The genera that most contributed to the biodiversity index were Acaulospora for Quebrada del Portugués and Glomus for Narváez Range. High diversity values were observed in the Yungas forests, particularly in the spring (rainy season). We concluded AMF differed in species composition and seasonal sporulation dynamics in the Yungas forests.
Assuntos
Fungos/isolamento & purificação , Micorrizas/isolamento & purificação , Árvores/microbiologia , Argentina , Biodiversidade , Fungos/classificação , Fungos/citologia , Micorrizas/classificação , Micorrizas/citologia , Rizosfera , Estações do Ano , Esporos Fúngicos/classificação , Esporos Fúngicos/citologia , Esporos Fúngicos/isolamento & purificaçãoRESUMO
In Argentina the Yungas forests are among the ecosystems most affected by human activity, with loss of biodiversity. To assess the arbuscular mycorrhizal (AM) colonization and the arbuscular mycorrhizal fungi (AMF) spore numbers in these ecosystems, the roots of the most dominant native plants (one tree, Alnus acuminata; three herbaceous, Duchesnea indica, Oxalis conorrhiza, Trifolium aff. repens; and one shrub, Sambucus peruviana) were studied throughout the year from two sites of Yungas forests. Assessments of mycorrhizal colonization (percent root length, intraradical structures) were made by washing and staining the roots. Soil samples of each plant species were pooled and subsamples were obtained to determine AM spore numbers. The herbaceous species formed both Arum- and Paris-type morphologies, whereas the tree and the shrub species formed respectively single structural types of Arum- and Paris-type. AM colonization, intraradical fungi structures and AMF spore numbers displayed variation in species, seasons and sites. D. indica showed the highest AM colonization, whereas the highest spore numbers was observed in the rhizosphere of A. acuminata. No correlation was observed between spore numbers and root length percentage colonized by AM fungi. Results of this study showed that Alnus acuminata is facultatively AM. The AM colonization, intraradical fungi structures and AMF spore numbers varied in species depending on phenological, climatic and edaphic conditions.
Assuntos
Alnus/microbiologia , Fungos , Magnoliopsida/microbiologia , Micorrizas/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Árvores , Argentina , Biodiversidade , Ecossistema , Fungos/crescimento & desenvolvimento , Fungos/isolamento & purificação , Magnoliopsida/classificação , Rosaceae/microbiologia , Estações do Ano , Solo/análise , Microbiologia do Solo , Esporos Fúngicos/isolamento & purificação , Trifolium/microbiologiaRESUMO
Molecular genetic analysis was applied to 162 individuals of 37 half-sib selected families belonging to six provenances of Eucalyptus dunnii Maiden in a provenance/family trial. The individuals were selected by a trait selection index and genetic diversity criteria were later applied for designing seedling seed orchards. Genetic diversity and its distribution, as well as relationships among individuals, were assessed on the basis of nine microsatellite loci and 243 amplified fragment length polymorphism markers. High diversity was found with both kinds of markers. Clear-cut genomic patterns of identification (fingerprinting) were obtained for each individual. Genetic differentiation estimates consistently showed low differentiation among provenances (R(ST1) = 0.069, theta(P) = 0.026 and F(CT) = 0.035) and great differentiation among families (R(ST2) = 0.223, theta(S) = 0.174 and F(SC) = 0.164). A high proportion of the total variation was observed within families (around 80% by both marker analyses), suggesting that orchard design should be based on individual or family selection rather than on provenance selection, and that individual ranking by both trait selection index and molecular genetic diversity criteria should be considered. A selection procedure for a seedling seed orchard design is proposed.