Modeling the spread of Fusarium oxysporum f. sp. passiflorae in simulated physical microenvironment

Abstract

The plant pathogenic fungus Fusarium oxysporum f. sp. passiflorae (FOP) causes severe losses to the Brazilian passiculture. As a soil inhabitant, the fungus spreads at the micro spatial scale (microspread) via mycelial growth and colony expansion. The pathogen expansion rate is affected by the spatial distribution of inoculum sources available, as well as by environmental factors. The objective of this study was to model the in vitro dynamics of FOP by simulating its microspread, under the effect of pH and osmotic potential, in controlled physical environments formed by agar sites spatially distributed in a triangular lattice. An additional experiment evaluated the effect of a heterogeneous environment on FOP microspread. This setting was represented by different fractions of sites with high and low nutritional content. A percolation theory was used to determine the limits of pathogen spread where critical distances are associated with a critical probability of site colonization. The logistic dose-response model was fitted to growth curves with the parameters estimated based on non-linear regression. We found that nutritional state of sites affected FOP microspread. In particular, a heterogeneous environment reduced their rate of microspread and consequently could reduce epidemic progress rate. This study contributes new biological knowledge and information to further improve disease management.