Control of Anthracnose by Chitosan through Stimulation of Defence-Related Enzymes in Eksotika II Papaya (Carica papaya L.) Fruit

The ability of chitosan to induce disease resistance in harvested Eksotika II papaya fruit was investigated in relation to the activities of several defence-related enzymes. Harvested papaya fruit were dipped in various concentrations of chitosan solutions (0.5, 1.0, 1.5, 2.0%) along with an untreated control and stored at 12 ± 1°C and 80-90% relative humidity for 15 days. Disease incidence and the activities of defence-related enzymes were monitored during storage. Compared with untreated fruit, chitosan treatments significantly reduced the severity of disease in fruit inoculated with Colletotrichum gloeosporioides. The activities of defence-related enzymes peroxidase, chitinase, β-1,3-glucanase and total phenolic compounds were all significantly enhanced in 1.5 and 2.0% chitosan treated papaya fruit as compared to the control and 0.5% chitosan. Therefore, it could be suggested that postharvest decay in papaya can be minimized by chitosan application on a commercial scale.