Extratos de cascas de maracujá e de laranja na indução de resistência em cafeeiro contra a ferrugem e em tomateiro contra mancha bacteriana

Abstract

The induction of resistance in plants against disease is an alternative method instead of pesticides, as active the resistance mechanisms in plants. It is hypothesized that extracts derived from orange and passion fruit peels, are able to induce resistance against a wide range of pathogens. These wastes contain appreciable amount of pectin, which can be fragmented, physical and/or enzymatically in oligogalacturonides (OGAs), a potent elicitor of defense response in plants. Our aim was to evaluate the effect of extracts made of orange and passion fruit peels in the protection and induction of resistance in coffee plants against Hemileia vastatrix and in tomato plants against Xanthomonas vesicatoria. Coffee and tomato seedlings were sprayed with extracts of orange peels (L) and passion fruit peels (M), inoculated and not inoculated with Cladosporium cladosporioides (cc), at the concentrations of 100% and 50%. Seven and four days later, the plants were challenged with H. vastatrix and X. vesicatoria respectively. In the coffee assay, the best results of protection were the extracts L50% + cc and L50%, and in tomato, were M50% e M50% + cc. These extracts showed low inhibition of fungal germination and bacterial growth. In the coffee experiment, we observed an increased in the enzymes, ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT), polyphenoloxidase (PPO), and peroxidase (POX) activities. Moreover, higher contents of total soluble phenolic. Treatment of tomato plants with M50 + cc and M50 showed an increase of defense enzymes activities, SOD, CAT, POX, PPO and FAL (phenylalanine ammonia-lyase), in comparison with water treated control. We also observed increased in the lignin depositions and chlorophyll contents. The extracts of orange and passion fruit peel showed satisfactory levels of protection, possibly because there was recognition of OGAs by the plants, which activate defense responses. Therefore, the extracts of orange and passion fruit peel were effective in the protection and induction of resistance to coffee rust and tomato bacterial spot.