Abstract

ROMERO MONTES, Gaspar; LOZOYA SALDANA, Héctor; FERNANDEZ PAVIA, Sylvia  and  GRUNWALD, Niklaus J.. Phytophthora infestans Oospore Distribution in Soil of the Toluca Valley, Mexico. Rev. mex. fitopatol [online]. 2011, vol.29, n.1, pp.25-38. ISSN 2007-8080.

Phytophthora infestans soilborne oospores can survive in the soil for years in an unclear distribution. To determine their spatial distribution in soil in the Toluca Valley, Mexico, potato plots cv. 'Alpha', with and without foliage-sprayed fungicides were established. Final disease severity was 35 and 100%, and the average number of oospores was 1.15 and 1.26 per gram of soil in plotswith and without fungicides, respectively. Marginal aggregates were observed in both plots (Lloyd and Morisita index; 1.42 with fungicide, 1.48 with no fungicide). The analysis of spatial autocorrelation showed immediate significant positive correlation (p≤0.05) to 1 m in the plot without fungicide, while in the plot with fungicide the correlation was at 4 m with no directionality. Spatial dependence was observed across rows; in the plot with fungicides it occurred at short distances (3.6 m) and at 135° azimuth in the plot without fungicides. There were differences among treatments when comparing the maximum distance in which there was spatial correlation among quadrants; 3.6 and 27 m with and without fungicide. Foliage disease severity did not influence the concentration of oospores in soil, but it did over spatial distribution, aggregation, and spatial dependence.

Keywords : Potato; Solanum tuberosum; late blight; epidemics.

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