Pg. 1-4 A mini-review: Post-harvest diseases in litchi and their control

The litchi fruit development and maturation process follows a sigmoidal pattern when quantified in terms of fruit weight. The respiratory fluxes reveal a non-climacteric pattern. Maturation stage is indicated by size and colour. A more accurate indicator is considered to be the sugar:acid ratio. The major factors reducing storage-life and marketability are pathological decay and pericarp browning. Low temperature storage is effective in reducing the rate of pathological decay, whereas is ineffective in preventing pericarp cell death. Pericarp cells die as a result of moisture loss. Consequently, the aril (pericarp) rapidly becomes brown and brittle. Post-harvest sulphur dioxide treatment is successfully used to prevent aril browning. This treatment is effective in controlling certain post-harvest rots. Recent research indicates, however, that it may promote blue mould colonisation of the pericarp during and after transit storage.

Blue mould occurring during and after transit storage was a particular problem during the 2001/2002 season. This mini-review summarises some literature pertaining to the control of the post-harvest diseases occurring in litchi.

Lin et al. (1998) explored the changes of oxidation and peroxidation in harvested litchi fruit. The changes may be of relevance in the consideration of preserving treatments. The ascorbic acid content of the pericarp and juice decreased during the period from harvest until seven days after harvest. The glutathione content of the juice showed a similar pattern, but the glutathione content of the pericarp increased during the first three days after harvest, before decreasing. Malondialdehyde, a product of lipid peroxidation, increased significantly after harvest. Superoxide dismutase activity decreased as malondialdehyde accumulated. The increase in peroxidase activity and malondialdehyde accumulation in the pericarp after harvest were regarded to be indicators of fruit senescence.

Summary:

• Litchi is a highly perishable fruit, and post-harvest diseases significantly reduce its shelf life and market value.
• Major post-harvest diseases include anthracnose, stem-end rot, and fruit rot, caused by fungi such as Colletotrichum gloeosporioides, Botryodiplodia theobromae, and Alternaria alternata.
• These diseases often develop during storage and transportation, leading to fruit decay and economic losses.
• Anthracnose is the most common disease, causing dark, sunken lesions on the fruit surface.
• Stem-end rot affects the pedicel region, resulting in browning and softening of the fruit.
• Fruit rot is characterized by soft, watery decay and can be caused by several fungal pathogens.
• Factors influencing disease development include high humidity, temperature, mechanical injury, and poor handling practices.
• Control measures include proper harvesting techniques, careful handling, and post-harvest treatments such as fungicide application, hot water treatment, and use of biocontrol agents.
• Integrated disease management strategies combining chemical, physical, and biological methods are recommended for effective control.
• Research is ongoing to develop resistant litchi varieties and improve post-harvest management practices.