Manejo de patógenos em melancia (Citrullus lanatus L.).

Abstract

Watermelon is a cucurbit with great socioeconomic importance. Its cultivation is negatively influenced by root diseases caused by fungi that infect seeds, such as Fusarium sp. Currently, disease management uses pesticides to control pathogens, which can provide resistance to them, alternative methods of pathogen control come as a viable option for this replacement. The present work aimed to evaluate the efficiency of essential oils and the biocontrol by Saccharomyces cerevisiae in the culture of watermelon. The work was conducted at the Phytopathology Laboratory of the Federal University of Paraíba. In the in vitro experiment, essential oils of lemongrass, copaiba, lemon balm, fennel, ginger, mint, basil and moringa were used, diluted in Potato-Dextrose-Agar medium at a concentration of 1%. The plates were incubated for seven days with a 12-hour photoperiod at 25 ± 2 ° C. The variables studied were mycelial growth rate index, mycelial growth inhibition percentage, sporulation and sporulation inhibition percentage, the experimental design was completely randomized. The mycelial growth was distributed in ten repetitions, while the sporulation data were performed in five repetitions. For the control with S. cerevisiae (Fleischmann® Biological Yeast), watermelon seeds from the cultivar Crimson Select Plus were used and submitted to disinfestation. The tested yeast concentrations were 0; 0.5; 1.0; 1.5 and 2.0 g / L. For health testing the seeds were incubated in Petri dishes containing a double layer of sterile filter paper, moistened with sterile distilled water. Twenty seeds were distributed per plate, in ten repetitions, kept in incubation at a temperature of 25 ± 2 ° C for a period of seven days. In the germination test, Germitest® paper moistened with sterile distilled water in the proportion of 2.5 times its dry weight was used, composed of four repetitions of fifty seeds per treatment. The material was incubated in a B.O.D. regulated at a temperature of 25 ° C ± 2 and a 12-hour photoperiod. The first evaluation took place 24 hours after the assembly of the germination experiment and was carried out until the fourteenth day. The incidence of fungi associated with watermelon seeds, percentage of germination, first germination count, germination speed index, hard and dead seeds and abnormal seedlings were evaluated. Seedlings were also analyzed, verifying the dry matter of roots, aerial part, and seedlings and length of roots, aerial part and seedling, treated with S. cerevisiae. The design used was completely randomized. The essential oils of fennel, mint and basil were effective in controlling Fusarium sp. in vitro. Presenting an inhibitory effect on mycelial growth and sporulation of the pathogen. S. cerevisiae has been shown to cause no harm to watermelon seeds at a concentration of 1.5 g. L-1 having increased root system mass and germination speed.