This is a final report for the Horticulture Innovation Lab project "Developing a postharvest alternative to fungicide in Sri Lanka." This project provides an alternative postharvest disease control approach to fungicide in conventional and organic mango and papaya production. This project brought together two parallel research programs: the use of natural coating and herbal extracts in Sri Lanka and efforts in Hawaii to use natural epiphytic microorganisms to control postharvest diseases.
This final project report includes an introduction to the project and its objectives, a project narrative, and a final report on the project indicators.
Report Narrative, submitted by Robert Paull:
Anthracnose and stem rot pathogens of mango and anthracnose pathogen of papaya were isolated from host tissue in accordance with Koch’s postulates, and pure cultures maintained. Cultures have been submitted to Gene Tech Ltd., for confirmation of the identification and genetic sequence of the pathogens. Six herbal extracts were obtained from Link Natural Pvt. Ltd. and screened against the pathogens. Two extracts were selected as being effective in inhibiting growth of the 3 respective organisms.
Selected herbal extracts were blended with the Industrial Technology Institute (ITI) edible wax coatings at different concentrations and tested for in vivo control of growth of the respective pathogens. Determination of the shelf life of the combined wax formulation was completed.
Having secured adequate supplies from our Industry partner Link Natural Pvt Ltd.Ͳof the selected herbal extracts, we preceded with the scheduled larger scale in vivo trials on mango and papaya. Success was achieved with in vivo trials using a new wax formulation where cinemaldehyde was incorporated in place of the herbal extracts into the original ITI wax formulation.
Three yeast isolates that were earlier shown to have potential biological activity were further tested in vivo on papaya fruit obtained from commercial grower. Half the treated and inoculated fruit were stored at 10°C for 10 days before ripening at ambient temperature. In addition to the yeast isolates, 0.5% thyme oil, 1.5% medium molecular weight chitosan and Sri Lankan wax were also tested for their postharvest disease control activities.
When the biological agents were applied on the same day as the pathogen inoculation, the antagonistic activity was not noticeable in papaya ripened at ambient temperature without cold storage. Neither thyme oil nor yeast isolates reduced the infection of Collectotrichum. The yeast isolates #581 and #1061 effectively reduced the Anthracnose development in papaya after cold storage. Initial studies indicated that the application time of the control agent influenced the effectiveness its antagonist activity. The biocontrol agent was more effective if applied later, if cold storage was not involved. All three yeast isolates tested, #581, #961 and #1061 showed antagonistic activity against Collectotrichum when applied one day after pathogen inoculation in papaya ripened at ambient temperature. However, when the papaya were stored at 10°C before ripening, only yeast isolate #1061 was effective in reducing the Collectotrichum infection.
Introductory workshops were conducted in three mango and papaya production areas. The team established links with growers Vidhatha Officers in Borrugodawatte, Thambuthegamma and Palagala in Kallawawe and took this opportunity to introduce the concepts of good postharvest handling procedures. A Stakeholder Workshop was also held in Colombo to introduce the project objectives to exporters and larger growers of these commodities. The latter program was timed to coincide with the visit of the US collaborators.
Scheduled workshops were conducted to demonstrate the effectiveness of the new cinemaldehyde incorporated formulation to Vidhatha Officers and samples were given to 20 officers to take back to their respective locations for further trials with growers and collection agents. As a consequence of this, a distribution agent / supplier of mangoes and papaya to exporters is interested in manufacturing the new wax formulation and using it in his operations and negotiations are in progress at present.