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Title:   Author  item
                                            FERNANDEZ-PAVIA, S - UNIV MICHOACANA, MEXICOitem
                                            Grunwald, Niklaus

                                                         - *Nik*item
                                            DIAZ-VALASIS, M - CIR-CENTRO INIFAP, MEXICOitem
                                            CADENA-HINOJOSA, M - CIR-CENTRO INIFAP, MEXICOitem
                                            FRY, W - CORNELL UNIV, NY
  Submitted to: Plant Disease
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 8/14/2003
                                    Publication  Date: 1/1/2004
                                    Citation: Fernandez-Pavia, S.P., Grunwald, N.J., Diaz-Valasis, M., Cadena-Hinojosa, M., Fry, W.E. 2004. Soil-borne oospores of phytophthora infestans in central mexico survive winter fallow and infect potato plants in the field. Plant Disease 88:29-33.Interpretive Summary: Oospores are sexual, reproductive structures produced by oomycetes such as the potato late blight pathogen Phytophthora infestans. Oospores can serve as a means of survival of these organisms over a winter as they have thick, double walls that protect the spores. Survival and infectivity of oospores in soils naturally infested with P. infestans oospores were studied in central Mexico. Oospore concentration, viability and infectivity varied among soils collected during the intercropping period in different locations of central Mexico. In some soils, oospores were infective regardless of the time at which they were collected during the intercropping period. However, oospore viability and infectivity decreased following two years of intercropping. This study confirms that oospores can survive over the winter and infect plants in the following growing season in the central highlands of Mexico.
                                Technical Abstract: Survival and infectivity of oospores in soils naturally infested with P. infestans oospores were studied in central Mexico. Sporangia were selectively eliminated from soil samples to determine infectivity attributable to the presence of oospores. Selective elimination of sporangia was achieved by two cycles of drying and wetting the soil. Oospore concentration, viability and infectivity varied among soils collected during the intercropping period in different locations of central Mexico. In some soils, oospores were infective regardless of the time at which they were collected during the intercropping period. However, oospore viability and infectivity decreased following two years of intercropping. The number of stem lesions and initial disease severity were significantly higher in soils with moderate oospore infestation compared to soils with low infestation. Our study confirms that oospores can survive intercropping periods and serve as a source of primary inoculum in the central highlands of Mexico.


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