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Made available in DSpace on 2015-03-26T13:58:40Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1058323 bytes, checksum: 6b28eb55ea2237955a72ef93867127be (MD5) Previous issue date: 2013-12-17 / Black Sigatoka, caused by Mycosphaerella fijiensis, is one of the most detrimental diseases for banana plantations in Brazil and worldwide. Although its occurrence in the state of Minas Gerais (MG) was first reported in 2004, the fears of economic disaster to banana growers never materialized along the past ten years. There is a clear paradox in this case, for a disease known to be devastating to this crop. Here this paradox is examined in detail and a narrative of the events that preceded and followed the first reports of the disease in MG. The initiatives taken by federal and state agencies to control the spread of the disease are discussed as well as the reasons and body of legislation behind the decisions that were taken along the years. A visit was made to the Zona da Mata region in Minas Gerais in areas regarded as being "positive" for the occurrence of the disease was performed. Interviews with banana growers in this region as well as extension workers, scientists and other professionals involved with the issue since 2004 were made. In addition, we analyzed data from surveys carried out by different groups at different occasions after the supposed outbreak in 2004. Evidence shows that the disease did not progress to new areas, and in 2007 it was not found in the areas in municipalities that are still strangely considered as "positive for the occurrence of disease". All reports from such studies (published or not) mention the contradiction between the predictions of a disastrous expansion of the disease and the observed continuation of the status quo for banana plantations for all areas in MG. Although awkward, the more acceptable hypothesis is that mistakes in identification of the pathogen have been originally committed. The final elucidation of the paradox is discussed and suggestions for modifying the federal and state legislation and regulations in order to repair the present situation and prevent the emergence of similar situations in the future are presented. / A Sigatoka-negra, causada por Mycosphaerella fijiensis, é uma das doenças mais prejudiciais à cultura da bananeira no Brasil e no mundo. Embora sua ocorrência tenha sido relatada pela primeira vez em 2004 no Estado de Minas Gerais, o temido desastre econômico esperado para os bananicultores do estado, passados dez anos, não se confirmou. Há um claro paradoxo neste caso, para uma doença sabidamente devastadora para a cultura. Realizou-se aqui um estudo deste paradoxo, pretendendo-se construir uma narrativa dos eventos que antecederam e se seguiram a esta ocorrência em MG, avaliando-se como as iniciativas para o controle da disseminação da doença foram conduzidas pelos órgãos de defesa agropecuária federal e estadual e como foram embasadas suas decisões, bem como discutindo o impasse gerado pelas imperfeições da legislação em vigor a cada tempo. Uma visita à região da Zona da Mata mineira em , em que foram feitas entrevistas com bananicultores desta região, assim como técnicos e profissionais envolvidos com o tema e que participaram de forma efetiva dos trabalhos conduzidos a partir de 2004. Além disso, analisaram-se os dados de levantamentos e monitoramentos realizados no período subsequente a 2004, mostrando que a doença não avançou para novas áreas, e que a partir de 2007 ela não foi encontrada nas áreas que ainda Todos os estudos posteriores a 2004 (publicados ou não) citam a contradição entre as previsões sobre um avanço do fungo e a observada continuação do status quo para a bananicultura mineira. A hipótese mais aceitável, embora embaraçosa, é a de que equívocos na identificação do patógeno tenham sido cometidos. A resolução final da situação paradoxal que se vive nesta questão em Minas Gerais é discutida e sugestões para a modificação da legislação e normas federais e estaduais de modo a corrigir este problema e problemas futuros são apresentadas.

Leaf diseases are an integral part of banana production. While currently not a cause for major concern in South Africa, many of these diseases van reach epidemic proportions and cause severe crop loss. To determine the present status of leaf diseases in South Africa, a survey was conducted in the five banana-growing regions of the country. The study indicated the following: Yello Sigatoka, caused by Mycosphaerella musicola was the most prevalent disease and occurred in all five the regions. Mycosphaerella speckle and Cordana leaf spot, caused by M. musae and Cornana musae respectively, were present in four regions. Cladosporium speckle, caused by Cladosporium musae, was found only in the Levubu area. Various other fungi, mainly saprobes and endophytes, were also isolated. The most commonly encountered species included Alternaria alternate, Colletrichum gloeosporioides, Nigrospora oryzae, N. sacchari, N. Spaerica, Pestalotiopsis sp., Phoma glomerata, Selenophoma asterina and S. juncea. Following morphological identification of the pathogenic species, monoconidial isolates were established from representative isolates of each and their virulence confirmed in artificial inoculation studies. The identity of M. musciola and Cladosporium musae was verified molecularly by means of species-specific primers and/or sequencing of the ITS region. Validation of the identity of Cladosporium musae constitutes the first report of Cladosporium speckle on banana in South Africa. Sequence data of the ITS region of isolates from Mycospaerella speckle lesions indicated that the symptoms are caused by two species, M. musae and one closely related to M. colombiensis, the latter previously described only from lesions on leaves of Eucalyptus urophylla in Colombia. / Dissertation (MSc (Microbiology))--University of Pretoria, 2002. / Microbiology and Plant Pathology / unrestricted