Effect of Lead Excess in Soil on the Disease Severity of Fusarium oxysporum f. sp. radicis-lycopersici (FORL) on Tomatoes. Regression Models for Estimation

S. Maneva, T. Vatchev

Abstract: Effect of the lead (Pb) level in the soil on the manifestations of Fusarium crown and root rot caused by F. oxysporum f. sp. radicis-lycopersici (FORL) was investigated in greenhouse conditions. Two factors of influence were applied: different levels of lead contamination of soil (0, 80, 160 and 240 mg.kg-1) as well as cultivation period (90 or 120 days) of tomato plants, cv. Ideal. Disease severity of FORL was estimated using six point scale (0-5) depending of the percentage infected root parts. It was found a positive correlation between the level of Pb and level of FORL infection and negative between the infection and the second factor, as the correlation was not linear. Infection increases with the level of Pb up to 160 mg.kg-1, and then decreases. Time of cultivation (till days 120 days from planting in contaminated soils) decreased the intensity of infection and longer than this time increased it. The status of infection was described by single-factor and two-factor regression models with satisfactory accuracy (R = 0.973, R = 0.972, respectively). Based on the first model was estimated that the highest degree of infestation occurs in 158 mg.kg-1 Pb in soil. With two-factor model had described the behavior of FORL infection for values of the two factors beyond experimental.

Keywords: Fusarium oxysporum; lead soil contamination; mathematical model; tomato plants

Date published: 2017-02-15