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Doctoral Thesis
DOI
https://doi.org/10.11606/T.11.1990.tde-20210104-185831
Document
Author
Full name
Maria Luiza Braz Alves
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 1990
Supervisor
Title in Portuguese
Adaptabilidade de linhagens de Alternaria porri (Ellis) Chif. resistentes a iprodione obtidas in vitro
Keywords in Portuguese
ALLIUM
FUNGOS FITOPATOGÊNICOS
LINHAGENS
MANCHA PÚRPURA
MEIOS DE CULTURA
RESISTÊNCIA AO FUNGICIDA
Abstract in Portuguese
Trinta e três isolados de Alternaria porri foram avaliados quanto à resistência a iprodione através do método de fungicida incorporado ao meio-de-cultura, os quais não apresentaram crescimento micelial em meio contendo 100 e 1000 ppm do produto, observando-se no entanto, a presença de setores resistentes nas concentrações testadas. Linhagens resistentes a iprodione, obtidas em laboratório a partir destes setores, mostraram um alto nível de resistência ao fungicida e alta estabilidade, mantendo a característica resistência após 15 transferências em meio isento do fungicida. O tamanho do inóculo, a concentração do fungicida e o período de incubação influenciaram o surgimento de setores resistentes in vitro. A frequência de linhagens resistentes em uma população sensível é baixa, só aparecendo após longo período 5 de incubação (9 dias) numa concentração aproximada de 105 esporos/ml. A adaptabilidade das linhagens resistentes, avaliadas através dos parâmetros: crescimento micelial, esporulação, competitividade e patogenicidade, de um modo geral foi menor nas linhagens resistentes. Testes de patogenicidade através de inoculação de sementes possibilitou melhor visualização da diferença entre as linhagens sensíveis e resistentes e a avaliação precoce de níveis de resistência do cultivares. As linhagens resistentes a iprodione mostraram resistência cruzada aos hidrocarbonetos aromáticos quintozene e dicloran e aos dicarboximidas procymidone e vinclozolin. Os fungicidas dichlofluanide e iprodione + thiram mostraram-se mais eficientes tanto para as linhagens resistentes quanto para as sensíveis a iprodione. O tratamento de sementes previamente inoculadas com iprodione + thiram, erradicativamente, reduziu o índice de doença em plântulas, mais acentuadamente que o tratamento com o fungicida iprodione isolado, tanto para as linhagens sensíveis quanto para as resistentes.
Title in English
Adaptability of iprodione resistant strains of Alternaria porri (Ellis) Chif. obtained in vitro
Keywords in English

Abstract in English
Thirty three isolates of Alternaria porri were evaluated with respect to iprodione resistance by using the method of fungicide incorporation into the culture medium. These isolates did not show mycelial growth at the concentrations of 100 and 1000 ppm of the product, the presence of resistant sectors at the tested concentrations being however observed. Iprodione resistant strains obtained from these sectors in the laboratory showed a high level of resistance to the fungicide and stability, maintaining the resistance character after 15 transfers on medium without the fungicide. The size of inoculum, the fungicide concentration and the incubation period influenced the appearance of resistant sectors in vitro. The frequency of resistant strains in a sensible population was low. They only appear after a long period of incubation (a days) at a concentration of approximately 105 espores/ml. The adaptability of resistant strains, evaluated by their mycelial growth, sporulation, competitiveness and pathogenicity, was in general lower than that of the non-resistant ones. Pathogenicity tests performed through seed inoculation gave a better differentiation between sensible and resistant strains with respect to early resistance levels. Iprodione resistant strains showed crossed resistance to the aromatic hidrocarbons quintozene and dichloran and to the dicarboximides procymidone and vinclozolin. The fungicides dichlofluanide and iprodione + thiram were more efficient for both the sensible and resistant strains. Erradicant seed treatment with iprodione + thiram reduced seedling disease index more pronouncedly the treatment with iprodione alone, for both sensible and resistant strains.
 
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Publishing Date
2021-01-07
 
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