Estrutura genética, agressividade e sensibilidade a fungicidas de populações de Phytophthora infestans das regiões sul e sudeste do Brasil / Genetic structure, aggressiveness and fungicide sensitivity of Phytophthora infestans populations from the south and southeast regions of Brazil

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

12/11/2010

RESUMO

The knowledge about the genetic structure, aggressiveness and sensitivity to fungicides of the current population of Phytophthora infestans can be useful to delineate strategies for the management of potato and tomato late blight. A total of 166 isolates were collected from six states of Brazil, in three periods: 1998/2000, 2003/2005 and 2008/2010. The isolates were assayed with microsatellite markers, mitochondrial haplotype (mtDNA) and phenotypic traits such as mating type, differences in aggressiveness and sensitivity to commonly used fungicides. Temporal analysis revealed changes in the population across the years. The distribution of mating types changed and isolates of A1 and A2 were found in the same potato field in two locations. Additionally, a new mtDNA haplotype was found associated with A2 isolates. Recombination signal was detected only in 03/05. To test the hypothesis that genetic changes altered host specificity of the isolates, eight isolates, four from potato (PG) and four from tomato (TG) were characterized based on five epidemiological variables: incubation period (IP), latent period (LP), lesion area (LA), infection frequency (IF) and sporulation capacity (SC). In leaflets, no differences in aggressiveness were detected between PG and TG. However, differences in LA and SC were detected between PG and TG inoculated in potato and tomato stems. Highest values of LA (2.87 cm2) were recorded for PG in both hosts and for SC values when PG were inoculated in tomato stem (1599.14 sporangia/cm2). Sensitivity to six fungicides was evaluated: mancozeb, chlorothalonil, propamocarb-HCl, fenamidone, dimetomorph and mandipropamid. Sixty eight isolates were accessed for propamocarb-HCl sensitivity and 62 isolates for mancozeb, chlorothalonil, fenamidone, dimethomorph and mandipropamid. No insensitivity was detected to mancozeb and chlorothalonil and it was observed a positive correlation between EC50 values of both fungicides. Among the systemic fungicides the highest EC50 values were observed for propamocarb-HCl, and the frequency of less sensitive isolates was highest in the South region. There was no evidence of resistance to the other systemic fungicides, and no evidence of cross-sensitivity among the different groups of fungicides.

ASSUNTO(S)

fitopatologia phytophthora infestans controle manejo doença phytophthora infestans control disease management

ACESSO AO ARTIGO

Documentos Relacionados