Alterações fisiológicas de genótipos de mandioca infectados por Phytopythium sp.

Abstract

Soft root rot is a disease caused by a pathogen that inhabits the soil, infection in the roots is associated with the opening of lesions occurring slight blackout symptoms or necroses, the aerial part may or may not present symptoms. The objective was to evaluate the biochemical and physiological response of the defense of cassava genotypes infected by Phytopythiumsp., in relation to source/drain. The experiment was conducted with stem cutting seeds previously characterized as resistant and susceptible to soft rot (BRS Poti and CPATU 530, respectively), both with and without the inoculation of Phytopythiumsp. The severity of the disease was analyzed, the determinations of gas exchange, chlorophyll a fluorescence, pigment content, starch and malondialdehyde, catalase enzymatic activity, ascorbate peroxidase, peroxidase and polyphenoloxidase. The genotype CPATU 530 promoted higher root Índices with infected area, with a mean of 18,69 % on the 34 Dait of experiment. Os maiores valores médios dos parâmetros A, gs, E e Ci / Ca foram obtidos em BRS Poti infectados, observou-se que os parâmetros estão associados à eficiência fotoquímica do PSII. The concentrations of Cia, starch in leaf, catalase and ascorbate in leaves and roots were not altered. It was observed an increase of 42.52% of lipid peroxidation in CPATU 530 infected, also showed an increase of 84.19% in the activity of peroxidase in infected plants and BRS Poti increase of 185.98% in the activity of the polyphenoloxidase in the infected treatment, showing that the enzymes that regulate secondary metabolism reflect plant resistance. The presence of oomycete in the roots in the tuberization phase caused a change in the source-sink ratio, resulting in an increase in A. possibly due to stomatal factors in response to stimuli from infected roots.