Browsing by Author "Zapata Quiroga, Mario Eduardo"

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    Diversity and historical biogeography of colletotrichum (ascomycota, glomerellales) species from natural and semi-natural forests in South-Central Chile.
    (Universidad de Concepción, 2024) Zapata Quiroga, Mario Eduardo; Palfner, Götz; Damm, Ulrike; Rodríguez Serrano, Enrique
    Colletotrichum is one of the most prevalent and economically significant plant-pathogenic genera worldwide. A considerable number of species cause anthracnose on a wide host range, including woody and herbaceous plants. While most studies focus on species infecting crops of high commercial interest, there are few studies on wild plants. The diversity of Colletotrichum on native trees in natural and semi-natural forests in Chile has been insufficiently studied, although the genus has been frequently detected in native forests by the by the Servicio Agrícola y Ganadero (SAG), the national plant protection organization. However, some of these strains are conserved in the Chilean Collection of Microbial Genetic Resources (RGM) and were available for a comprehensive study, especially since most of them have only been identified at the species complex level. Interestingly, many of them show a close relationship with species known from Oceania suggesting a potential biogeographical connection. This dissertation therefore examines the existing knowledge of Colletotrichum in natural ecosystems, the diversity of species in native forests in south-central Chile, and the most probable origin of their diversification. To achieve these objectives, first, a synthesis of published research on Colletotrichum in native vegetation is provided, following the PRISMA protocol for systematic reviews. Secondly, the identification of Colletotrichum species occurring in native woody plants was determined using a polyphasic approach that included the comparison of morphological characters, multi-locus phylogenetic analyses, and coalescent-based species delimitation methods. Finally, the most probable temporal and spatial diversification of the Chilean Colletotrichum species and the complexes to which they belong was inferred through a biogeographic approach using a time-calibrated phylogeny and a Dispersal-Extinction-Cladogenesis (DEC) model of range evolution. The main results revealed that research on Colletotrichum in natural ecosystems is scarce, predominantly conducted in tropical regions, and mainly focused on ecological aspects. The diversity study based on 50 strains examined in the C. acutatum and C. boninense complexes identified six known species, which were recorded as C. arboricola, C. brassicicola, C. godetiae, C. pyricola, C. rhombiforme and C. roseum. Additionally, four species new to science were described as C. americanum, C. laurosilvaticum, C. palki, and C. perseicola. The biogeographic analyses indicated a potential Chilean-Patagonian origin of the C. acutatum complex and a clear Holarctic origin of the C. boninense complex. Most of the Chilean species with disjunct distribution in Oceania, or those closely related to oceanic taxa, according to our analysis, diverged from common ancestors that inhabited the Chile-Patagonian, Neotropical, and Novozealandic floristic realms. However, the divergence time of these ancestors was too late to support a Gondwanan origin. Therefore, the current distribution was explained by in long-distance dispersal events that occurred after the Gondwana Era.
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    Efectos del calentamiento en agua sobre la elasticidad y trabajo en tracción y comprensión perpendicular a la fibra en madera verde de Eucalyptus globulus.
    (Universidad de Concepción., 1997) Zapata Quiroga, Mario Eduardo; Valenzuela Hurtado, Luis
    Se estudió el efecto inmediato de distintas temperaturas y tiempos de calentamiento en agua sobre los parámetros de elasticidad y energía-trabajo en tracción y compresión perpendicular a la fibra en madera verde de Eucalyptus globulus para dos zonas radiales en el fuste. Ambos parámetros disminuyeron con la temperatura y el tiempo de calentamiento, y variaron entre la zona exterior e interior del fuste. A través de una regresión lineal múltiple, se relacionó la elasticidad y el trabajo con los factores estudiados y otras variables físico mecánicas de la madera. Dentro de este mismo estudio, se observó la variación de la elasticidad y el trabajo con el ángulo de inclinación del anillo de crecimiento en la probeta. Probetas denominadas como tangenciales en tracción perpendicular, registraron valores mayores a las radiales, mientras que en compresión perpendicular, la situación es inversa.
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