Disease control and storage-life extension in tropical fruit

• Kasetsart University, Thailand

Tropical fruits ripen, deteriorate in appearance and eating quality and succumb to postharvest diseases very rapidly after harvest. Postharvest deterioration is a major constraint to profitability for the domestic market, and to the expansion of existing and new export markets, particularly since many tropical fruits have poor tolerance of cold storage. International community pressure within developed and developing countries, continues to rise for a reduction in the use of postharvest chemicals on fruit. In Australia, without the postharvest treatment with hot water and benomyl, the mango industry would not have developed. However, the availabilty of benomyl and other postharvest fungicides may be restricted in the future, so storage conditions and fruit characteristics at harvest are important topics for research in Australia as well as other tropical countries such as Thailand.

Progress has been made in the identification of pathogens causing diseases of tropical fruit, and studies were carried out on the most significant causes of loss, anthracnose and stem end rot (SER) and in the development of control measures utilising hot water and fungicides. This has opened the way for further studies on the mechanism of tropical fruit disease and development of strategies that minimise the use of chemicals.

This project will build on ACIAR Project 8844 and will involve Australian scientists at the CSIRO Division of Horticulture, Queensland and the Queensland Department of Primary Industries (QDPI); and Thai scientists at the Department of Plant Pathology, Kasetsart University (KU), Bangkok and Chiang Mai University (CMU). Strategies to be examined are management techniques to reduce infection by postharvest pathogens, prolong fruit storage life and enhance fruit resistance to disease; the roles of antifungal compounds and host structural barriers in the regulation of infection and invasion by the pathogens causing stem-end rot and anthracnose; and the biological control of anthracnose.

Research on fruit storage will involve determination of preharvest influences on postharvest storage potential and disease incidence and severity for a variety of tropical fruits including mango, avocado, longan and lychee. Scientists will investigate the effects of postharvest water relations, calcium treatments and carbon dioxide pulsing. Modelling techniques will also be used to assess the predictability of modified atmosphere development.

The mode of infection of SER pathogens will be investigated for several tropical fruits by researchers who will determine the effects of water stress and defoliation on SER development, cultivar resistance, and assess the interactions between endophytic SER and non-SER fungi.

Researchers involved in the biological control of anthracnose will develop techniques for the selective isolation of biological control agents from tropical fruit; select yeasts with biocontrol activity against fungi causing anthracnose; and determine the mode of action of selected microorganisms.