Background:

Vanilla (Vanilla planifolia Jacks.) is a source of vanillin. Fusarium oxysporum f. sp. vanillae (Fov) is the main health problem of the crop.

Objective:

The effect of a thermal gradient on the in vitro development of pathogenic and non-pathogenic F. oxysporum strains of V. planifolia was evaluated.

Methods:

Two strains of F. oxysporum with high pathogenicity, two with moderate pathogenicity and two with non-pathogenicity of V. planifolia were selected. The effect of a gradient between 23 and 32 °C on the production of mycelium and spores of the strains in potato dextrose broth was evaluated for 15 days. The data were processed using ANOVA, Tukey and Kruskal Wallis tests.

Results and conclusions:

A significant difference was found in the biomass of five Fov strains, except for highly pathogenic strain JAGH3, which grew abundantly at the evaluated temperatures. In general, the highest mycelial weight was obtained at 28 and 30 °C, the lowest at 25 and 32 °C. Spore production of all six strains increased significantly at 23 and 32 °C. It is concluded that Fov develops optimally at 28 and 30 ºC in in vitro conditions, with greater sporulation at 23 and 32 ºC.

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