Ponente
Descripción
Chitosan is a glucosamine polymer with activity as an antimicrobial compound and also as an elicitor of defense responses in plants. The effect of chitosan on different life cycle stages of Phytophthora nicotianae, an Oomycete that causes severe damage in tobacco and tomato crops, was evaluated in the present study. Addition of this compound, from 0.5 to 2.5 g.L-1, to culture media decreased the isolates mycelial growth. The colony pattern and the hyphae diameter were not affected by the polymer; however, a reduction in the number of the sexual reproduction structures (oospores) was observed at the lowest concentration (0.5 g.L-1) tested. Low chitosan concentration stimulated sporangia production, while high concentrations reduced this number. The sporangia length/width ratio was not affected by the polymer. Indirect germination of sporangia was completely abolished with 1.5 g.L-1 of chitosan. Zoospores incubated with different polymer concentrations did not germinate and they were not able to infect tomato plants roots at the lowest concentration tested (0.5 g.L-1). Moreover, chitosan activated tomato plantlet protection against P. nicotianae infection when applied as a foliar application (0.1 and 1 g.L-1) prior to inoculation. The induced resistance was concurrent with increased activity of phenyl-propanoid pathway markers. Taken together, these results show that it is possible to control the spread of this pathogen in solanaceous crops with the application of this compound.
