Effect of treatment with essential oils on anthracnose disease development, quality and shelf life of banana (Musae spp.) Fruits

Abstract

Banana fruit experiences a different problem from that of most other fruits, because ripe bananas are very perishable. Postharvest diseases such as anthracnose reduced the annual yield of banana fruit. Losses from postharvest banana diseases are severe in Ethiopia. The application of fungicides to fruits after harvest to reduce decay has been increasingly curtailed by the development of pathogen resistance to many key fungicides, the lack of replacement fungicides, negative public perception regarding the safety of pesticides and consequent restrictions on fungicide use. The objective of this study was to determine the efficacy of different essential oils on prolonging the storage life of banana fruit and to reduce postharvest losses by controlling anthracnose (C. musae). Essential oils were extracted by hydro distillation method using Clevenger type apparatus, and then each essential oil was tested in three different concentrations. The first part of the experiment (in vitro) focused on determining the effect of essential oil on mycelia growth of C. musae and it was carried out by using food poison method. The treatments consisted of essential oils of basil (0.10%, 0.15% and 0.20%), cinnamon (0.025%, 0.05% and 0.075%) and rosemary (0.20%, 0.25% and 0.30%) on potato dextrose agar and incubated at 25o c. In the second part (in vivo) fruits were infected artificially by C. musae spore, and then banana hands were sprayed with emulsions of the essential oils of 0.10%, 0.15% and 0.20% Ocimum basilicum, 0.20%, 0.25% and 0.30% Rosmarinus officinalis and 0.025%, 0.05% and 0.075% Cinnamomum zeylanicum and then stored at room temperature. The experimental design for this particular phase was two-factor factorial with the two factors being banana variety (Giant Cavendish and Williams) and the essential oils with different concentrations (basil at 0.10%, 0.15% and 0.20%, cinnamon0.025%, 0.05% and 0.075% and rosemary at 0.20%, 0.25% and 0.30%) and with three replications. Response measurements collected were mycelial growth inhibition (%), physiological weight loss (%), pulp to peel ratio (g), firmness, total soluble solid (°Brix), titratable acidity(%),total soluble to titratable acidity ratio, dry matter (%),pH , disease incidence (%) and percent disease index (%). A significant (P < 0.01) inhibition of mycelial growth of C. musae was observed in all treatments of essential oil as compared to the control after 7 days of incubation at 25o c. All essential oils used for this experiment had significant (p<0.05%) effects on both disease incidence and percent disease index but had no significant effect on most of physico- chemical characteristics evaluated. From all essential oils used, basil at 0.20% concentration showed the minimum percent disease index (26.67%) compared with the other treatments 19 days after storage. It can thus be concluded that among the essential oils used, basil oil proved to be effective during in-vivo test; applied at 0.20% (v/v) reduced the development of C. musae growth, maintained the freshness of the banana fruits and increased shelf life of Giant Cavendish and Williams banana fruits for up to 19 days without affecting the physico-chemical properties. Thus, further research efforts are needed to integrate the current findings to be used in integrated disease management methods in the near future.