Infecção de folhas de cafeeiro por Cercospora coffeicola, identificação de genes para produção e auto-resistência à cercosporina e progresso da cercosporiose em sistemas de cultivo orgânico e convencional

• Ano de defesa: 2011
• Autor(a) principal: Souza, André Gomes Coelho de
• Orientador(a): Maffia, Luiz Antônio
• Banca de defesa: Pereira, Antonio Alves , Rodrigues, Fabrício de ávila , Daub, Margaret Elizabeth
• 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: Coffea arábica; Mancha de olho pardo; Patogênese; Epidemiologia
• Palavras-chave em Inglês: Coffea arabica; Brown eye spot; Pathogenesis; Epidemiology
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA
• Link de acesso: http://locus.ufv.br/handle/123456789/1030

Coffee is considered an important commodity worldwide. Diseases are considered a limiting factor in coffee yield. Cercospora leaf spot, caused by Cercospora coffeicola, is considered a relevant disease in coffee crops. This study aimed at understanding: i- the C. coffeicola infection process on coffee leaf by microscopic analysis; and ii-identify if genes associated with cercosporin production and auto-resistance in other Cercospora spp. were present and had the same functions in C. coffeicola, and generate mutant(s) of C. coffeicola with differential cercosporin production; and iii- the progress of cercospora leaf spot epidemics on three different coffee production systems (organic, organic under shadow, and conventional). To the first aim both adaxial and abaxial leaf surfaces were inoculated with a conidial suspension of C. coffeicola. Samples were collected from 4 to 168 h, and at 35 days after inoculation. Germinated conidia showed positive tropism to stomata where attempted penetrations occurred. Appressoria were not observed. After penetration, C. coffeicola colonized the lacunous parenchyma both inter and intracellularly. Sporulation occurred through or around the stomata. To achieve the second aim, six C. coffeicola isolates from Brazilian fields representing organic and conventional production systems in the Minas Gerais state were evaluated for their ability to produce cercosporin in vitro. The highest producing isolate was selected to identify homologs of a polyketide synthase (CTB1) and ABC transporter (ATR1) genes involved in production and sensitivity to cercosporin in C. nicotianae, respectively. The C. coffeicola CTB1 and ATR1 genes were amplified using degenerate and standard PCR primers. These genes were sequenced and compared to C. nicotianae sequences available on GenBank. In addition, C. coffeicola was successfully transformed with a GFP construct and with a CTB1 disruption. Growth and sporulation of these disrupted strains were determined on PDA and PDA supplemented with hygromycin. The sporulation and growth were variable among isolates, and disrupted strains unable to produce cercosporin did not differ significantly from the wild type for either growth or sporulation. To achieve the third aim, during 4 years (November/2004 – October/2008) the severity (SEV), incidence (INC), leaf fall (LF) and leaf growth (LG), were evaluated to understanding the cercospora leaf spot epidemic progress on three different coffee production systems: organic (LO), organic under shadow (LOS) and conventional (LC), at Ervália-MG, Brazil. The higher SEV, INC, LF, GL, area under disease progress curve, and maximum disease occurred under LC and upper branches. However, the opposite results occurred under LOS and lower branches. The period of greater disease intensity, LF, and GL were the months between May-July, July-September and October-January, respectively. The ARMA model from time series analysis was able to describe the cercospora leaf spot progress during all the years studied and the production systems evaluated.