Produtos alternativos controlam a podridão negra e aumentam a atividade de enzimas ligadas à defesa em couve

Abstract

Xanthomonas campestris pv. campestris (Xcc) which causes black rot in cabbage, is a serious disease in Brazil. Its management is a challenge for urban agriculture. In order elaborate an alternative solution for managing this disease, we evaluated five different products: whey (10% v / v), lime sulfur (100%), bio fertilizer (20% v / v), bordeaux mixture (100%), raw milk (10% v /v) and water as control. The products were applied every 15 days, starting from 35 days after transplantanting. The bacterium was inoculated eight days after the first application. The experiment was conducted in the summer, wet and warm period. The severity of of black rot was evaluated (5, 10 and 15 days after the appearance of the first symptom in the control. The data obtained was used to calculate the area under the disease progress curve (AUDPC). In order to determine the benefits of all five treatments, we evaluated nutraceutical-related variables (DPPH radical, crude fiber, crude protein, lipids and total phenolic compounds). For the two treatments resulting in highest disease control, the induced resistance potential of the products was determined by the activit ies of phenylalanine ammonia lyase (PAL), catalase (CAT), peroxidase of guaiacol (POX), lignin and total phenolic compounds. In field evaluation, the treatments of raw milk and bio fertilizer presented the lowest AUDPC, reducing the disease by 39 and 51%, when compared to the control. In the treatment with raw milk, we verified increased crude protein and fiber in leaves compared to the control when plants where inoculated with Xcc, increase in DPPH radical and total phenolic compounds, and, in the treatment with bio fertilizer, increased lipids in the experiment without bacteria. With the application of bio fertilizer, we verified higher activity of POX and CAT, when compared to the control and plants treated with Xcc. In quantification of total phenols and DPPH the best or most efficient in free radical scavenging without pathogen inoculation were biofertilizer which the percentage inhibition was higher than 84%, then the raw milk and whey, 80% and 77% respectively. Therefore, the application of bio fertilizer is a promising alternative for the control of black rot in cabbage, and is also beneficial for human food quality.