Variabilidade de Cercospora coffeicola em Minas Gerais com base em compatibilidade vegetativa e produção de cercosporina

• Ano de defesa: 2007
• Autor(a) principal: Martins, Ricardo Brainer
• Orientador(a): Maffia, Luiz Antônio
• Banca de defesa: Alfenas, Acelino Couto , Teixeira, Hudson
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Fitopatologia
• Departamento: Etiologia; Epidemiologia; Controle
• País: BR
• Palavras-chave em Português: Café; Cercosporiose; Mutantes nit; Diversidade genética; Marcadores genéticos
• Palavras-chave em Inglês: Coffee; Cercospora coffeicola; Nit mutants; Genetic diversity; Molecular markers
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA
• Link de acesso: http://locus.ufv.br/handle/123456789/1078

The Cercospora leaf spot is considered an emergent disease in the coffee culture. However there is little information about the biology and ecology of the causal agent, Cercospora coffeicola. The aim of this study was to characterize the variability of pathogens populations associated to coffee trees in both conventional and organic systems in three Minas Gerais regions. A hierarchical sampling plan was performed with the following levels: 1. State geographical regions (Sul, Triângulo, and Mata); 2.Crop system (organic and conventional); 3. Plantings. Out of 420 monosporic isolates collected, 90 were randomly selected. To characterize the variability, two markers were used: vegetative compatibility and production of cercosporin in vitro. Vegetative compatibility was estimated by the use of nit mutants, auxotrophic mutants unable to use nitrate as the only nitrogen source. Twenty eight vegetative compatibility groups (VCG) were identified through complementary tests. Out of the 28 VCG s, 10 were multimembers and included 56,6% of the isolates and 18 included just one isolate that were restricted to specific plantings. Considering the distribution of VCG s among the levels studied, a variance analysis was implemented and a diversity index was estimated. Higher part of variation found (92.05%) was attributed to isolate. There was no difference in diversity for the levels we analyzed. Members of one VCG occurred in the three regions, whereas members of other groups occurred in one or two regions. At in vitro assays, the production of cercosporin was evaluated, and the concentration ranged from 1.71 to 35.327 μMol/isolate. The percentage of total variance among isolates was 1.9, 7.8, and 48.9% for region, plantings and isolates levels, respectively. No effect of crop system (P=0.88) was detected in the variability. Dissimilarity measures were estimated among isolates (Malahanobis index) and the Unweighted pair-group method with arithmetical averages (UPGMA) was performed to determine groups of similar cercosporin production (CPG). Isolates with an low and median levels of production of predominated in the population. Considering the markers used, there are evidences that the studied population has a high variability and the region, crop system and plantings have no effect on the variability.