Modelagem da microdisseminação de fusarium oxysporum f. sp. passiflorae em ambientes heterogêneos simulados

Abstract

Fusarium oxysporum f. sp. passiflorae (FOP) is a fungus that causes serious damage to the Brazilian passiculture. Being soilborne, this pathogen can microspread by mycelial growth and colonies expansion. The spread depends on the spatial distribution of colonized and non-colonized sites, as well as the influence of environmental factors. The objective of this study was to model an in vitro dynamics involved in the process of microspread of FOP in simulated heterogeneous environments. Pathogen spread was evaluated in a system formed by agar sites spatially distributed in a triangular lattice. Initially blank tests were conducted. Later analysis of different environmental factors in microdissemination of FOP were carried out: pH, sources of inorganic nitrogen, osmotic potential and plant materials. Finally, has conducted a test simulating the heterogeneity between colonization sites. To determine the limit of pathogen spread, the percolation theory was applied, in which critical distances were associated to a critical probability of colonization among sites. Logistic Dose Response model (LDR) was fitted by nonlinear regression with the aid of TableCurve 2D5.01 program to the obtained curves. Results indicated that the nutritional state of sites had an influence on the microspread of FOP. Critical greater distances were obtained with alkaline pH, use of ammonium sulfate as inorganic nitrogen source, low osmotic potential and the use of plant materials as source of nutrients. With respect to heterogeneity, the results demonstrate that heterogeneous environments can prevent invasion of FOP, since they reduce the critical distance reached by the pathogen.