Integrated management of postharvest Fusarium rot of gladiolus corms using hot water, UV-C and Hyptis suaveolens (L.) Poit. essential oil

Abstract

Gladiolus corms artificially inoculated with the pathogen Fusarium oxysporum f. sp. gladioli were treated with hot water, UV-C or essential oil of Hyptis suaveolens (L.) Poit., alone and in combinations, to control the population growth of the pathogen after storage of 4 and 12 weeks. In vitro efficacy of hot water, UV-C or essential oil was tested and it was observed that a hot water treatment at 55 °C for 25 min or a UV-C treatment with a dose of 3.63 kJ m −2 were sufficient to inhibit germination of conidia. In vitro fungitoxic efficacy of the essential oil also clearly showed that 0.6 μL cm −3 of oil was sufficient to completely inhibit the fungal growth and 0.4 μL cm −3 oil completely inhibited conidial germination. In vivo efficacy of hot water, UV-C or essential oil was determined by calculating the log 10 transformation of CFU g −1 corm after storage periods of 4 and 12 weeks. Hot water alone at 55 °C for 30 min significantly reduced the CFU as compared with the control. UV-C treatment (dose 4.98 kJ m −2) was sufficient to reduce the population of the fungus. An essential oil treatment of 0.8 μL cm −3 for 2 weeks was significantly effective in reducing the pathogen population during storage. Integrated treatments of hot water (55 °C for 30 min), UV-C (dose 4.98 kJ m −2) and essential oil (0.8 μL cm −3) for 2 weeks were more promising than their treatments alone, after storage for 4 and 12 weeks. GC–MS analysis of the H. suaveolens essential oil, showed that 24 compounds were present, the main ones being1,8-cineole (44.4%), β-pinene (11.7%), β-caryophyllene (10.0%), camphene (5.7%) and β-myrcene (5.3%).