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Title:   Author  item
                                            FERNANDEZ-PAVIA, S - UNIV DE MICHOACANitem
                                            Grunwald, Niklaus

                                                         - *Nik*item
                                            DIAZ-VALASIS, M - INIFAP, MEXICOitem
                                            CADENA-HINOJOSA, M - INIFAP, MEXICOitem
                                            FRY, W - CORNELL UNIV
  Submitted to: Plant Disease
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 8/14/2003
                                    Publication  Date: 11/1/2003
                                    Citation: FERNANDEZ-PAVIA, S.P., GRUNWALD, N.J., DIAZ-VALASIS, M., CADENA-HINOJOSA, M., FRY, W.E. SOIL-BORNE OOSPORES OF PHYTOPHTHORA INFESTANS IN CENTRAL MEXICO SURVIVE INTERCROPPING PERIODS AND INFECT POTATO PLANTS IN THE FIELD. PLANT DISEASE. 88:29-33. 2003.Interpretive Summary: The potato late blight pathogen Phytophthora infestans produces sexual reproductive structures called oospores. At this point it is not clear how important oospores are in initiating epidemics and as a means of survival of the pathogen. Oospores a double walled resting structures and it would be expected that they can survive winter periods. Survival and infectivity of these oospores in soils naturally infested with oospores were studied in central Mexico where these pathogen originated from. 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.
                                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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