Efeitos de produtos químicos na inibição do crescimento de Paracidovorax citrulli

Abstract

The melon tree (Cucumis melo L.) is a crop of great economic importance for Brazil, especially for the Northeast, region responsible for more than 90% of melon production. In recent decades, melon production has grown exponentially due to favorable climatic conditions with low humidity and little rain, thus producing excellent quality fruits for consumers. However, the crop is susceptible to several phytopathogens that compromise its productivity, leading to a decline in fruit quality. Among these, the bacterium Paracidovorax citrulli stands out, which causes watery spot, a disease whose symptoms can be observed at any stage of development of the melon tree, leading to the loss of several crops. Although there are treatment recommendations to control this bacteriosis, they have not been shown to be effective, leading to the need to carry out new research to find more efficient solutions. Therefore, the objective of the study was to test in vitro the antibacterial activity of four phytosanitary products, Kasumin, Fegatex, Kocide and Quimifol Titanium S, which are used to control water spot. In the in vitro test, in microtiter plates, two isolates of P. citrulli (CCRMAc1.43 and CCRMAcM.1) and three concentrations of phytosanitary products were used, with eight repetitions, with growth inhibition being evaluated after 48 hours by reading for absorbance analysis. To confirm the inhibitory effect, suspensions of each treatment were seeded in NYDA culture medium and inoculated into melon fruits. All product concentrations inhibited the growth of P. citrulli isolates CCRMAc1.43 and CCRMAcM.1. Fegatex® and Kocide® demonstrated a bactericidal effect, with inhibition of bacterial growth from the first concentration, which were 3,000ppm and 0.3g, respectively, with no growth observed in the culture medium and no water spot symptoms in the fruits. The Kasumin product demonstrated bacteriostatic action with bacterial growth inhibited from the second concentration (5,000ppm), but with symptoms of the disease at all concentrations, with the possible occurrence of the condition of viable but non-culturable cells (VBNC) once that no growth was observed in the culture medium. When treated with Quimifol Titanium S, the isolates had their growth inhibited from the second concentration (0.8mL/150mL) and the bacteria grew in the culture medium only when treated with the first concentration of the product (0.09mL/150mL), inducing symptoms in the fruit also at this concentration.