Essential plant oils in reducing the intensity of soft rot in chinese cabbage

Abstract

The action of essential oils in reducing soft rot in Chinese cabbage, and their influence on the colorimetry and physicochemical characteristics of the vegetable were evaluated. In the greenhouse, plants of the cultivar Natsume were sprayed with 11 oils selected in preliminary tests for phytotoxicity: bergamot, lemongrass, copaiba, Eucalyptus citriodora, blue gum, fennel, ginger, spearmint, sweet orange, lemon and clary sage (0.5%) and also the antibiotic Mycoshield® (3 g L-1). After 72 hours the plants were inoculated with Pectobacterium carotovorum subsp. carotovorum (Pcc-c). The oils and the Mycoshield® significantly reduced (P≤0.05) the severity (SEV) and the area under the disease progress curve (AUDPC). The oils of bergamot, copaiba, E. citriodora, spearmint and sweet orange were then tested for the stability of their effectiveness in the control of three isolates of P. carotovora subsp. carotovorum. These oils reduced the SEV (30.5 to 38.6%) and the AUDPC (23.1 to 26.6%) with no differences between them or the Mycoshield® (SEV 45.2 and AUDPC 32.8%), except for the copaiba (20.3%) which was less effective than the antibiotic in the reduction of the AUDPC. In vitro, only Mycoshield® inhibited the pathogen. None of the treatments altered the colorimetry, levels of ascorbic acid or pH of the leaves of the Chinese cabbage. The spearmint oil increased the total titratable acidity in the same way as the oils of sweet orange, E. citriodora and bergamot increased the total soluble solids. Therefore, spraying with the oils of bergamot, copaiba, E. citriodora, spearmint and sweet orange has potential in the control of this disease.