Indução de resistência em soja e controle de Pratylenchus brachyurus com fertilizante foliar a base de alecrim (Rosmarinus officinalis L.)

Abstract

The soybean is a crop of great importance for the Brazilian agriculture, however, it’s yield can be negatively affected by root system pathogens, such as the root lesion nematode Pratylenchus brachyurus. Due to the high difficulty in controlling this pathogen, alternative methods have been studied, such as the use of substances based on medicinal plants and nutrients with potential to induce resistance in plants. The objective of this work was to evaluate the nematicide effect of rosemary-based leaf fertilizer (Rosmarinus officinalis L.) and its effect on the resistance induction in soybean to control P. brachyurus. Treatments used were the doses 0; 1.5; 3; 4.5 and 6 g L-1 of foliar fertilizer “All Crim convencional™”, and 0.125 g L-1 of acibenzolar-s-methyl (ASM). In vitro experiments were performed to evaluate P. brachyurus mortality and, in vivo, evaluate the phenylalanine ammonia-lyase, polyphenol oxidase and peroxidase enzymes activity and, evaluate the agronomical (plant height, number of pods, grain mass and fresh root mass) and nematological parameters (total number of root nematodes and number nematodes per root gram), this last parameter was studied in two different growing seasons. The foliar fertilizer acted as a nematicide in the in vitro experiment. In the in vivo assays there was no effect from the treatments on plant height, number of pods and fresh root mass, however, there was an increase in the peroxidase activity three days after of 1.5 and 3.0 g L-1 of the tested product was applied, indicating resistance induction, as the total number of nematodes and number of nematodes per root gram reduced after the application, being more efficient than the control treatment with acibenzolar-Smethyl. Grain mass loss was observed after product application, possibly due to fitness cost of resistance induction.