Viabilidade de oósporos oriundos de cruzamentos de isolados brasileiros de Phytophthora infestans

• Ano de defesa: 2006
• Autor(a) principal: Cruzado, Zoila Rosa Magnolia Santa Cruz
• Orientador(a): Maffia, Luiz Antônio
• Banca de defesa: Teixeira, Hudson , Pereira, Olinto Liparini , Paula Júnior, Trazilbo José de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Fitopatologia
• Departamento: Etiologia; Epidemiologia; Controle
• País: BR
• Palavras-chave em Português: Phytophthora infestans; Oósporos; Requeima; Germinação
• Palavras-chave em Inglês: Phytophthora infestans; Oospores; Germination
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA
• Link de acesso: http://locus.ufv.br/handle/123456789/4426

Phytophthora infestans isolates were obtained from infected potato or tomato leaves and tomato fruits collected from the South, Southeast, Northeast, and Central-West regions in Brazil. Eleven isolates of the A1 mating type and four of the A2 were paired in culture media to assess production of oospores. After quantifying the number of oospores obtained from each pairing, two variables, number of oospores produced in culture medium (NOCM) and number of oospores extracted from the medium (NOEXT), were subjected to a partial diallel analysis with F1 s only, in order to estimate the fecundity of the crosses. Oospore viability was estimated with a plasmolysis in NaCl test and germ tube formation was determined in water agar. All crosses produced oospores. The number of oospores varied among the crosses and ranged from 233 to 3900/ml. The general combination ability (GCA) and specific combination ability (SCA) varied among isolates and were significant (P < 0.0001). For both NOCM and NOEXT the A2 mating type isolate with the highest GCA value was Pib-750. Among the A1 mating type isolates, highest GCA values were estimated for Pib-754 and Pib-742, based on the NOCM and NOEXT, respectively. Based on SCA, the best isolate combination for oospores production was between Pib-731 x Pib-755, for both variables. There was no clear trend regarding a possible geographical proximity effect on the fecundity of crosses. Although the crosses produced oospores, viability and germination rates were low, on average 0.3% to 0.03%, respectively. Despite the low viability, production of oospores can be a threat to potato and tomato crops as a source of genetic diversity for this pathogen.