Alternative and biological control of pathogens in watermelon seeds

Abstract

Watermelon is a cucurbitaceous plant with great socioeconomic importance. Its cultivation can be influenced by diseases caused by soil-inhabiting and seed-infecting fungi, such as Fusarium sp. The continuous use of pesticides in the management of diseases can cause the appearance of resistant pathogens. It was aimed to evaluate the efficiency of essential oils and the biocontrol by Saccharomyces cerevisiae in watermelon culture. The essential oils of lemon grass, copaiba, lemon balm, fennel, ginger, mint, basil and moringa were used at a concentration of 1% and diluted in potato-dextrose agar medium. The variables studied were: mycelial growth velocity index, mycelial growth inhibition percentage, sporulation and sporulation inhibition percentage. For the control with S. cerevisiae (Fleischmann® biological yeast) watermelon seeds cultivar Crimson Select Plus (Feltrin) were used. The yeast concentrations tested were: 0; 0.5; 1.0; 1.5 and 2.0 g L^-1. The following tests were performed: sanity; germination percentage; first count of germination; germination speed index; hard and dead seeds; abnormal seedlings; root, aerial part and seedling dry matter; and root, aerial part and seedling length, treated with S. cerevisiae and essential oils. The treatments with fennel, mint and basil were efficient in controlling Fusarium sp. in vitro, presenting inhibitory effect on mycelial growth and sporulation of the pathogen. S. cerevisiae did not cause any harm to watermelon seeds at the concentration of 1.5 g L^-1, and showed an increase in root system mass and germination speed index.