Species in the genus Calonectria (anamorph: Cylindrocladium) are euascomycetes in the order Hypocreales and are important pathogens of a wide range of plant hosts globally. At the outset, this thesis considers the literature pertaining to species of Calonectria and especially the importance of the biological, morphological and phylogenetic species concepts on the taxonomy of this group. It is clear that DNA sequence comparisons have revolutionised the taxonomy of Calonectria and literature also highlights the importance of a polyphasic approach to species identification. Studies in this thesis treat a number of forest nursery disease problems caused by Calonectria spp. and new species are consequently described based on DNA sequence comparisons, morphological characteristics and sexual compatibility tests. As a consequence several cryptic species were also identified in the genus. Therefore, a multigene genealogy was constructed for all Calonectriaspp. for which cultures were available and shown to group together in 13 subclades also supported by morphological similarities. As a consequence all Cylindrocladium spp. were circumscribed to the genus Calonectria, regardless whether the teleomorph state was present or not, based on new nomenclature regulations stated in Article 59. / Thesis (PhD)--University of Pretoria, 2010. / Microbiology and Plant Pathology / Unrestricted

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2017-06-22T11:26:41Z No. of bitstreams: 1 texto completo.pdf: 764280 bytes, checksum: d05cab1466cd8efeeae95e1353106805 (MD5) / Made available in DSpace on 2017-06-22T11:26:41Z (GMT). No. of bitstreams: 1 texto completo.pdf: 764280 bytes, checksum: d05cab1466cd8efeeae95e1353106805 (MD5) Previous issue date: 2016-07-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / A mancha-de-pteridis, causada por Calonectria pteridis, é, atualmente, uma das principais doenças foliares em plantações de eucalipto no Brasil. Em regiões de clima quente e úmido, a doença pode ser um fator limitante para o plantio de genótipos suscetíveis. O método mais eficaz de controle da doença no campo é o plantio de material resistente, o que requer o conhecimento da variabilidade genética e fisiológica na população do patógeno para a seleção de plantas. Neste trabalho avaliaram-se a diversidade genética e a agressividade de C. pteridis obtidos de vários clones de eucalipto em diferentes regiões do Brasil. Estudaram-se 90 isolados provenientes principalmente dos estados do Pará e Maranhão. Para o estudo da diversidade genética, dentre os 16 primers ISSR testados, empregaram-se cinco que foram polimórficos e reprodutíveis. Análises de diversidade genética permitiram identificar 33 genótipos entre os 90 isolados estudados, porém geneticamente próximos, indicando uma baixa diversidade entre eles. Para o estudo da agressividade inocularam-se em dois clones híbridos de Eucalyptus grandis x E. urophylla, sob condições controladas, 16 isolados selecionados com base na origem geográfica e na diversidade genética. A avaliação da severidade foi feita através do percentual de desfolha e por atribuição de notas de acordo com uma escala diagramática, sendo analisada a correlação entre elas. Não houve correlação entre a variabilidade genética e fisiológica, pois os indivíduos diferiram em agressividade. Houve uma alta correlação entre as duas formas de avaliação para apenas um dos clones utilizados. Os isolados GFP004, LPF059 e LPF294 foram os mais agressivos e devem ser empregados nas inoculações para selecionar plantas resistentes à mancha-de-pteridis. / Calonectria leaf blight caused by Calonectria pteridis, is, currently, one of the major foliar diseases of eucalyptus plantations in Brazil. In humid and warm regions, it may be a limiting factor for growing suscetible genotypes. The most effective method of disease control in the field is by planting resistant plant material, which requires knowledge of the genetic and physiological variability in the pathogen population for screening for plants. In this work we evaluated the genetic diversity and the aggressiveness of C. pteridis obtained by several eucalyptus clones in different regions of Brazil. We studied 90 isolates collected mainly from the states of Pará and Maranhão. To study the genetic diversity, among 16 ISSR primers tested, five who were polymorphic and reproducible were used. Genetic diversity analysis have identified 33 genotypes among the 90 isolates studied, but genetically related, indicating a low diversity among them. To study the aggressiveness, we inoculated into two hybrid clones of Eucalyptus grandis x E. urophylla, under controlled conditions, 16 isolates selected based on the geographic origin and genetic diversity. The severity assessment was performed using the percentage of defoliation and attribution of notes through a diagrammatic scale, and subsequently analyzed the correlation between them. There was no correlation between the genetic and physiological variability, because individuals differ in aggressiveness. There was a high correlation between the two forms of evaluation to only one of the clones used. The GFP004, LPF059 and LPF294 isolates were the most aggressive and should be used in inoculations to select plants resistant to Calonectria leaf blight.

Seed transmission of <i>Cylindrocladium parasiticum</i> was investigated as a possible explanation for the higher-than-expected incidence of Cylindrocladium black rot (CBR) of peanut in fields fumigated with metam sodium. Sixty-three commercial seed lots from Virginia production fields were examined for the presence of seed with speckled testae, a symptom of seed infection by <i>C. parasiticum</i>. Speckled seed was present in conditioned seed lots in 1998, 1999, and 2000 at an average rate of 1%. Soon after pods were harvested, the fungus was recovered from speckled seed at high frequencies. During winter seed storage, pathogen survival remained high in seed stored at -13 and 4 C, but declined in some seed stored at 15 C and ambient temperatures. Speckled and normal seed with and without fungicide treatment was planted in steam-treated soil in the greenhouse and metam-treated field plots in 1999 and 2000. Speckled seed treated with captan + pentachloronitrobenzene (pcnb) + carboxin transmitted the pathogen to emerging plants in the greenhouse and field. Transmission levels depended on the amount of viable inoculum present in seed at the time of planting. In the field, yield losses were significant when 20% or more of the seed planted was speckled. The low incidence of speckled seed in commercial seed lots would not result in a loss of yield for growers, but may contribute to disease spread. Testing of additional seed treatment fungicides indicated that fludioxonil, tebuconazole, and thiram may offer the best protection against disease spread from seed transmission of <i>C. parasiticum</i>. / Master of Science