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Avocado, Persea americana / Lauraceae
Postharvest Atmosphere Management
Avocado
The period of storage of avocados depends on the state of maturation in which the fruit was harvested and the careful handling. Those harvested completely ripe and those that did not reach their physiological maturation or complete development must not be stored.

The cooling technique offers the maximum effectiveness in the storage of avocados. The conditions recommended for storage are between 4 and 7 ºC and 80-90% of relative moisture. For green-mature fruit the temperatures are between 5-13ºC (with physiological or harvest maturation), depending on the cultivars and the period of time of low temperatures. Avocados with consumption maturation must be stored at temperatures of 2-4ºC. Even though avocados last up to 28 days under these conditions, they may go through some problems of softening, chilling injuries and physiological alterations, chiefly at low temperatures. In order to reduce the effect of these problems in long periods of storage they can be stored in controlled atmosphere, whose optimal conditions are 2% of oxygen, 10% of carbon dioxide and a temperature of 7,2ºC.

The application of ethylene is used to make the produce mature before going to the market; to consume it directly after its purchase.
Distribution
The same environmental conditions for preservation, are suitable for transport and distribution.
Postharvest Problems
After the harvesting, some problems caused by antracnosis, the branches’ blight and fruit rotting, the pedicel’s rotting, and other types of diseases may arise in post-harvest.

Antracnosis (Colletotrichum gloesporioides)
This disease is considered to be one of the most important. Apart from the damages and effects caused in the produce, it reduces the quality of the fruit during its trade, causing great losses.

The symptoms are clear circles and a firm rotting afterwards. The injuries have a variable size and a dark bright colour, and they could destroy the whole fruit. In advanced stages, these areas penetrate into the pulp.

A whole shipment could be destroyed in the warehouse; it occasionally attacks the leaves and branches, causing defoliation.

Fruit rotting
Caused by the fungus Dothiorella spp. that attacks the branches and the fruit. In the fruit, the infection may occur before or after the harvest. The rotting affects the pericarp with greater intensity and if it reaches the pulp it acquires a slightly watery consistency. While the rotting advances, the pericarp softens and the pulp is foul-smelling. In the end it rots and the fruit turns into a greenish-grey colour.

Other post-harvest diseases

Post-harvest diseases are the following ones:
- Leaf spot or avocado mottles (Pseudocercospora purpurea): This damage is frequent in avocados produced in Florida, EUA, the Caribbean, Brazil, Cameroun, and South Africa. At first, some white or green mottles arise (like small spots). Afterwards, under conditions of high levels of moisture the spot grows and acquires a coffee colour. They rarely grow more than 0.5 cm but many other organisms get into the fruit through the wounds, particularly fungi that cause antracnosis.

- Rot caused by Alternaria: It was in Israel where they found that Alternaria sp. causes rotting in the peduncle and in other parts of the fruit.

- Soft bacterial rot: It was also in Israel where they found this damage caused by Erwinia carotovora. The fruits affected have soft, dark and flat mottles usually occurring in the whole fruit. Gradually, the pulp becomes smooth and looses colour, giving off a foul smell.

- Rotting caused by Fusarium: This rotting is caused by different species of Fusarium. It is an important disease in Israel, South Africa, EUA, and the west of India. The damages caused by this fungus represent a way through which the fungi related to the peduncle’s rot get in, accelerating the damage.

- Rot caused by Phytophthora: It was found in Mexico and EUA, and identified as Phitophthora citricola. It affects the fruit placed in the low branches and it spreads by means of water splashed on the ground.
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