Controle da mancha bacteriana do maracujazeiro e alterações bioquímicas induzidas por produtos químicos, fertilizantes foliares e extratos vegetais.

Abstract

The passion fruit bacterial spot is widespread in the main producing areas in Pará State, but its control is not well estabilished yet. The use of induced resistance is a promissing alternative and can be used with other strategies to control plant diseases. The present work aimed to evaluate the effect of chemicals, leaf fertilizers and plant extracts to protect passion fruit against bacterial spot. The enzymatic mechanisms involved in the induction of resistance in passion fruit against Xanthomonas axonopodis pv. passiflorae were also evaluated. The chemicals oxytetracycline, fluazinam, mancozeb, copper oxychloride, acibenzolar-S-methyl, the fertilizers Fitoforce copper and Fitoforce plus and leaf extracts of Jackfruit and Indian mulberry were analyzed. In vitro tests results showed that the chemicals oxytetracycline, fluazinam, mancozeb, copper oxychloride and the fertilizers Fitoforce copper and Fitoforce plus completely inhibited the growth of the pathogen at all concentrations tested. The extracts of jackfruit and Indian mulberry inhibited the growth of bacteria between 45 and 63% of control, while the acibenzolar-S-methyl did not show any in vitro antimicrobial activity against X. axonopodis pv. passiflorae. All treatments reduced the severity of bacterial spot of passion fruit, with control over 54% differed significantly from the control, except for the Fitoforce plus that showed the control efficiency below 50%. The applications of acibenzolar-S-methyl, Fitoforce copper and jackfruit leaf extract increased the activity of peroxidase, chitinase and B-1,3-glucanase in yellow passion fruit.

The present research aimed to evaluate the effect of chemicals, leaf fertilizers and plant extracts on growth in vitro of Xanthomonas axonopodis pv. passiflorae and the severity of bacterial spot of passion fruit in greenhouse. The chemicals oxytetracycline, fluazinam, mancozeb, copper oxychloride and acibenzolar-S-methyl and the foliar fertilizers Fitoforce copper and Fitoforce plus and leaf extracts of jackfruit and Indian mulberry were used. For the in vitro tests, treatments were incorporated into the culture medium 523 (Kado and Heskett, 1970) on their respective strengths and assessments were performed by counting the number of colonies of the pathogen. The experimental design was completely randomized design with five replications. The tests on greenhouse treatment application were performed 2 days before inoculation of X. axonopodis pv. passiflorae for chemicals and 7 days before inoculation for fertilizers and extracts. In all tests, the experimental design was randomized blocks and the disease severity assessments were performed every 48 hours. In vitro assays, the chemicals oxytetracycline, fluazinam, mancozeb, copper oxychloride, fertilizer Fitoforce copper and Fitoforce plus completely inhibited the growth of the pathogen at all concentrations tested. The leaf extracts of Indian mulberry and of jackfruit inhibited the growth of bacteria between 47.85 and 63.43%, while the resistance inducer acibenzolar-Smethyl showed no action against X. axonopodis pv. passiflorae. At the greenhouse all treatments reduced the severity of bacterial spot of passion fruit, with control over 54% differed significantly from the control, except for fertilizer Fitoforce plus that showed a lower percent control efficiency, below 50%, and did not differ significantly from the control.

The effects of acibenzolar-S-methy], jackfruit leaf extract and Fitoforce copper were evaluated in reducing symptoms of bacterial spot of passion fruit, and the activity of peroxidase, chitinase and B-1,3-glucanase were determined. The treatments were applied seven days before inoculation of bacterial suspension at a concentration of 10º CFU / mL. The experimental design was randomized blocks. Evaluations of disease severity were made at intervals of 48 hours after inoculation. To obtain the enzymatic extracts and determination of enzymatic activity of chitinase, peroxidase, B-1,3-glucanase, leaf samples were collected at 3, 7, 10 and 14 days after treatment application. The acibenzolar-S-methyl, jackfruit leaf extract and Fitoforce copper significantly reduced the severity of bacterial spot of passion fruit, the best treatment for the bacterial disease control was provided by acibenzolar-S-methyl. The applications of acibenzolar-S-methyl, Fitoforce copper and jackfruit leaf extract increased the activity of peroxidase, chitinase and B-1,3-glucanase.