Métodos de inoculação e efeitos de Fusarium oxysporum f. sp. vasinfectum em sementes de algodoeiro

Abstract

The availability of seeds infected by fungi or other pathogens transmissible by this way is important for several purposes. This work was conducted to evaluate proceedings of inoculations and period of exposition of seeds to Fusarium oxysporum f. sp. vasinfectum through the water restriction technique. The following methods were compared: (1) seed immersion in a conidial suspension (106 conidia/mL) following incubation in substrate with an osmotic potential of-1.0 MPa; (2) atomization of a conidial suspension (106 conidia/mL) upon the substrate and on the seeds, and (3) direct contact of the seeds with the fungus mycelium, grown upon the substrate. All methods enabled to obtain seeds with different inoculum potential equivalent to different times, 24, 48, 72, 96 and 120 hours of seed expositions to the fungus. To evaluate the efficacy of infection, germination tests on roll paper and in soil/sand substrate and Blotter Test were applied. The most effective method was the immersion of seeds in inoculum suspension followed incubation in substrate with water restriction. The period of time that seeds should stay in contact with the pathogen, without affecting their physiological quality, was 53 h to 57 h. Copyright by the Brazilian Phytopathological Society.