166 research outputs found

    Species identification of Mycosphaerella leaf blotch disease (MLD) on Eucalyptus globulus in Portugal

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    ‚ÄúMycosphaerella leaf disease‚ÄĚ √© causada por esp√©cies de Mycosphaerella e v√°rios anamorfos. Em Portugal, esta doen√ßa foi largamente ignorada at√© 1998 quando foram verificados s√©rios estragos em planta√ß√Ķes comerciais de Eucalyptus globulus. O objetivo deste trabalho foi dar uma contribui√ß√£o ao levantamento inicial de ‚ÄúMycosphaerella leaf disease", clarificando a composi√ß√£o do complexo Mycosphaerella. √Č apresentada (Cap√≠tulo 1) uma panor√Ęmica da situa√ß√£o mundial e uma lista detalhada das esp√©cies detetadas em Portugal. As esp√©cies foram identificadas com base em m√©todos moleculares (Cap√≠tulo 2) e na sua morfologia (Cap√≠tulo 3). Adicionalmente, ao objetivo inicial desta tese, foi estabelecida uma primeira avalia√ß√£o da suscetibilidade de clones e fam√≠lias de eucaliptos em condi√ß√Ķes experimentais. /ABSTRACT - Mycosphaerella leaf disease is caused by species of Mycosphaerella and several anamorphic form genera that have been associated to Mycosphaerella. ln Portugal, this disease was largely ignored until 1998 when serious damage on commercial plantations of Eucalyptus globulus was reported. The aim of this work was to give a contribution to initial survey of Mycosphaerella leaf disease, clarifying the composition of Mycosphaerella complex. An overview of worldwide situation and a detail list of species reported in Portugal is presented (Chapter 1). Species were identified based on molecular methods (Chapter 2) and on their morphology (Chapter 3). Additionally, of the initial aims of this thesis, a first evaluation of clones and families eucalypts susceptibility in experimental conditions was established

    Studies on the eucalyptus leaf disease complex in Portugal

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    Native from south eastern Australia, Eucalyptus globulus is the main species in eucalypts plantations in Portugal. The most serious foliar disease in eucalypt plantations is linked to Mycosphaerella senso lato, which affects young trees in the juvenile phase foliage causing leaf necrosis. This disease results in reduced growth rate of the host and lower wood volume, thus causing significant productivity losses. The most common name for this disease was Mycosphaerella Leaf Disease that became inappropriate when most of the pathogens on eucalypts were re-distributed into several genera. The term "Eucalyptus Leaf Disease Complex" is now more appropriate. The overall aim of this thesis was to investigate the Eucalyptus Leaf Disease Complex in Portugal, focusing on species diversity, taxonomy and the role played by each species in the disease complex on Eucalyptus globulus. Literature on the Eucalyptus Leaf Disease Complex was reviewed and the species were distributed into several genera. A survey based on symptomatic leaves collected from several Eucalyptus globulus plantations and characterized by morphological and molecular tools provided an overview of species incidence and of the most frequent species in the disease complex. The present work reveals additional species of Mycosphaerella senso lato associated with eucalypt plantations in Portugal. Thus, five new records of Teratosphaeria and phylogenetically related species were added to the Iberian Peninsula, namely, Neodevriesia hilliana, for the first time on Myrtaceae; Quasiteratosphaeria mexicana, Teratosphaericola pseudoafricana, Teratosphaeria pluritubularis and Teratosphaeria lusitanica, a new species. Furthermore, new anamorphic structures were found and two new combinations were made. Regarding other genera, some species were observed for the first time, such as Cladosporium cladosporioides, Fusicladium eucalypti, Mycosphaerella madeirae, in the mainland. In addition to leave diseases, Teratosphaeria gauchensis was found causing a severe stem and trunk canker on Eucalyptus globulus. The aggressiveness of several species was compared to evaluate each species individually in the complex, permitting to distinguish different behaviours, from primary to secondary pathogens. Cladosporium cladosporioides, M. communis and M. lateralis, appeared to be more aggressive than Teratosphaeria nubilosa. In fact, contrary to the prevailing views on this disease complex, Teratosphaeria nubilosa is not the only species responsible for the disease, which clearly involves a complex of species acting together

    Strategies to combat Mycosphaerella Leaf Disease in Eucalyptus globulus plantations in Northern Spain

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    Eucalyptus globulus is widely planted in temperate regions to produce pulp for its high performance but few studies of the impact of Mycosphaerella Leaf Disease (MLD) have been documented. This study aimed to explore and provide knowledge on disease in the management of young Eucalyptus globulus stands in the north of Spain. The influences of subspecies, cloning, and fertilization on the degree of severity of the disease were analyzed. The study was conducted with different material plants of Eucalyptus globulus, of Australian origin, from other sources, open-pollinated families, clones, and families of controlled pollination. Each series tested different vegetal material, except for a number of control codes that were used as reference samples for MLD evaluation. Severity, height at which foliage changes from juvenile to adult, total height, and volume were all measured. There were significant correlations in the average MLD severity of families and provenances obtained from the different trials. ANOVA revealed important differences between subspecies of E. globulus. A correlation was found between the percentage of adult leaf and the severity. There were differences in the impact of MLD between plant material non-selected and selected by its tolerance (p < 0.0001). There was a significant effect on the severity between mature cuttings and families from seed non-selected in their tolerance to MLD. Their tolerance was lower than that achieved from seed selected by its tolerance to MLD. Genetic selection was shown as the best strategy since there are individuals exceptionally tolerant to MLD

    Mycosphaerella leaf disease on eucalypts in Western Australia - The diversity and impact

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    Eucalyptus plantation forestry in Western Australia (WA) is a relatively young industry and by the end of 2008, the total plantation estate (softwood and hardwood) was over 950 000 ha. The predominant plantation species is Eucalyptus globulus, native to south-eastern Australia. In Western Australia (WA), the most serious foliar disease of eucalypt plantations is Mycosphaerella Leaf Disease (MLD). However, little systematic sampling for MLD has been carried out in WA to determine its impact on plantations, yields, species involved or whether they are introduced or not. The overall aim of this thesis was to investigate MLD in south-western Australia with a particular focus on the species diversity, taxonomy and the impact on early growth on E. globulus. The increase in the number of Mycosphaerella and Teratosphaeria species associated with Mycosphaerella leaf disease (MLD) in E. globulus plantations in WA in the past decade has raised concern about the possible movement of pathogens between the native forests and plantations and vice versa. A survey of necrotic leaf spots collected from plantation and endemic eucalypts from WA and Queensland was conducted. Overall, ten new Eucalyptus host records for Mycosphaerella/ Teratosphaeria species were isolated from WA and five from Queensland. Significantly, M. nubilosa was isolated from E. grandis x resinifera and E. urophylla x globulus in WA. This is the first time M. nubilosa has been isolated from Eucalyptus hosts within the series Resinifera (see Chapter 2). An assessment of the number of fungi that may be contributing to MLD in E. globulus plantations in WA was undertaken (Chapter 3) and the changes in the number of species and their incidence since the first surveys were conducted. Four new records of Mycosphaerella were identified in this study; M. ellipsoidea, P. fori, M. suttoniae and M. tasmaniensis. Mycosphaerella ellipsoidea and P. fori are first records for Australia, and M. suttoniae and M. tasmaniensis are first records for WA. The current work shows an increase in the number of Mycosphaerella species associated with plantation eucalypts in WA and Australia. With the exception of M. cryptica, none of these species were known in WA prior to the commencement of large-scale E. globulus plantations, and with M. cryptica as the exception, none have a known impact on the major native eucalypts in the region. The ITS region of the type material of T. parva, M. grandis and M. gregaria using culture and herbarium specimens was sequenced and compared to existing sequences from GenBank (Chapter 4). This was the first study to examine and sequence the type material of M. grandis, T. parva and M. gregaria. As the sequences of the ITS region of M. grandis and T. parva were identical it was concluded that M. grandis be reduced to synonymy with T. parva. Mycosphaerella aurantia, M. buckinghamiae and M. africana also match the type sequence of M. gregaria. Therefore, these should all be synonymised to M. gregaria. Also, this study was the first to describe ITS sequence variation within the same Mycosphaerella isolate. The aim of Chapter 5 was to identify the infection pathway at the leaf surface using scanning electron microscopy and to determine the pathogenicity of M. marksii on E. globulus. The use of glycerol as a surfactant and its effect on ascospore viability was also assessed. However, this study was unable to confirm pathogenicity of M. marksii on E. globulus seedlings under laboratory conditions. However, M. marksii ascospores were able to germinate and enter E. globulus stoma 3‚Äď6 days after initial infection. Species-specific primers were successfully designed and tested for three Mycosphaerella species that occur on E. globulus in WA (Chapter 6). Meteorological conditions appeared to determine the defoliation of juvenile foliage and not MLD as levels of MLD remained relatively low throughout the trial period. The MLD levels increased throughout spring as warm wet conditions favoured the development of disease especially on the flush of new juvenile foliage. Also, new foliage emerged after late summer rainfall. As disease pressure mounted, the trees responded through defoliation. As temperatures increased and the juvenile foliage aged, there is likely to have been an increase in the defoliation of leaves. Therefore, by mid-summer defoliation levels reached a similar level to disease and insect damage. Following leaf defoliation and the emergence of new juvenile and adult leaves, the relative amount of disease on the trees decreased. This is because most of the disease was present on the older juvenile foliage which was shed. Field observations can be a reliable indication of disease progression. Although field observations at a branch level over exaggerated levels of MLD when there was a higher level of foliage, there was still a similar trend in the amount of disease when compared to the ASSESS program. Some experience in disease monitoring would indicate a more accurate assessment of MLD. It is interesting to note that the assessors tended to overestimate disease when MLD was at a higher level, and this also included the author. Infection studies of Uwebraunia dekkeri were conducted to confirm how this species enters E. globulus leaves and to determine its pathogenicity (Chapter 7). This study demonstrated that conidia of U. dekkeri could infect E. globulus leaves and that it is not a hyperparasite of M. cryptica or M. nubilosa. Conidiogenesis was both percurrent and sympodial and the phenomenon of anastomosis was observed for the first time on the leaf surface. The impact that MLD has on the wood volume has previously not been investigated in WA (Chapter 8). Through the application of pesticides and fungicides in the early stages of establishment at two plantations near Albany, tree volumes were significantly increased. However, the increase in wood volume would be offset by the pesticide and application costs. This study demonstrated that monitoring for pests and disease would be more effective than spraying of chemical treatments for the first three years. The regular use of chemical treatments is expensive to maintain and is proving to be environmentally unacceptable by some communities. This study also showed that spraying for low levels of MLD had little effect on disease incidence and/ or volume increase in E. globulus plantations in WA. The most important factors for a healthy plantation appear to be site selection, preparation and tree genetics. This study was the first to investigate the impact of MLD on the growth of Eucalyptus globulus plantations in WA. As part of this study, the biology, taxonomy and pathogenicity of the main species present in WA were investigated. The key findings were: i) the number, abundance and distribution of Mycosphaerella/ Teratosphaeria species in WA is not static and plantations should be continually monitored for the presence of new potentially threatening species; ii) spraying for MLD, although effective in reducing the prevalence and impact on growth, was not economically viable; and iii) intragenomic variation of the ribosomal genome may explain sequence variation observed in single spore isolates of Mycosphaerella/ Teratosphaeria and this has taxonomic implications. Further work would identify the impact the new records are having on the plantation estate and also if these species have the potential to spread into the neighbouring endemic forests. This study has provided a broader understanding of MLD in WA and the development of tools that could be used for further study

    Especies de Mycosphaerella y Teratosphaeria asociadas con la enfermedad Mycosphaerella de las hojas en Eucalyptus globulus en Portugal

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    Plantations of Eucalyptus globulus represent the main source of wood for the pulp and paper industry in Portugal and are affected by the complex of Mycosphaerella and Teratosphaeria species (Mycosphaerella leaf disease), which is an important foliage disease worldwide. This disease affect mainly young trees with juvenile-phase foliage, causing premature defoliation, decreased growth and wood production. Species of Mycosphaerella sensu lato reported on eucalypts in Portugal are M. communis, M. heimii, M. lateralis, M. madeirae, M. marksii M. walkeri, T. africana, T. molleriana, T. nubilosa and T. parva. In order to complete the survey, symptomatic leaves were collected from Eucalyptus globulus plantations. Morphological and molecular characterization was used to give an indication of the species occurrence and most frequent species (T. nubilosa) and the composition of the MLD complex that did not change after the latest review.Las plantaciones de Eucalyptus globulus representan la principal fuente de madera para la industria de pasta y papel en Portugal y se ven afectadas por el complejo de especies de Mycosphaerella y Teratosphaeria (enfermedad Mycosphaerella de las hojas), que es una enfermedad importante en todo el mundo. Esta enfermedad afecta principalmente a los √°rboles con fase juvenil de follaje, causando defoliaci√≥n prematura, disminuci√≥n del crecimiento y de producci√≥n de madera. Las especies de Mycosphaerella sensu lato descritas sobre el eucalipto en Portugal son M. communis, M. heimii, M. lateral, M. madeirae, M. marksii, M walkeri, T. africana, T. molleriana, T. nubilosa y T. parva. Con el fin de completar el inventario, se obtuvieron hojas sintom√°ticas de plantaciones de Eucalyptus globulus. Se ha utilizado una caracterizaci√≥n morfol√≥gica y molecular para identificar la presencia de especies, la especie m√°s frecuente (T. nubilosa) y la composici√≥n del complejo de MLD que no cambi√≥ despu√©s de esta √ļltima revisi√≥n

    Biomass losses caused by Teratosphaeria leaf disease in Eucalyptus globulus short rotation forestry

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    This article presents the results of a study that examines the loss of biomass and energy, per hectare, caused by Teratosphaeria leaf disease (TLD) in Eucalyptus globulus short rotation forestry. The 95 Eucalyptus globulus taxa analyzed are from seeds of open pollinated families of both Spanish and Australian origin. Tree height and diameter were measured and the crown damage index (CDI) assessed at 27 months of age. Taxa that have a certain tolerance to the disease have been identified. The taxon identified as code 283 is the one that shows lower CDI (42%) and with an average volume that exceeded 0.017 m3 at 27 months of age. Biomass losses were determined for each fraction of dry biomass of the tree (leaves, branches, twigs and bark) based on CDI. These losses were translated into terms of energy lost per hectare, depending on the CDI. A comparison was then carried out between the productivity of Eucalyptus globulus exhibiting various levels of TLD severity and poplar and willow clones used for bioenergy in Europe. In our region, the results show that despite the losses of biomass associated with TLD, Eucalyptus globulus remains competitive as long as CDI values are lower than 56%
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