Citrus and its Post harvest losses
The role of horticultural crops in agriculture cannot be ignored. They play a vital role in the economy of a country. As well as concerned to Pakistan a lot of work is under process for this field. Private farms are working together with government institutes. As we move forward towards the pomology field, citrus is the leading fruit crop cultivated in Pakistan and its production is at number 6, all over the world with 2.10 million tons. 95 percent of Kinnow of world is from Pakistan.
Citrus is a genus belongs to rutaceae family. Its order is sapindales. According to Swingle, who classify citrus into 3 genuses, Citrus with 16 species, Poncirus with 4 species and Fortunella with only one spp. More than 100 varieties of citrus are being used as fresh, processed or in juice form. Its different varieties are also used for pickle for flavoring food item and for medicinal properties. It is native to South-East Asia as long as about 4000 years BC. In Pakistan grapefruit, mandarin, sweet orange, bitter orange, lime, lemon, rough lemon and kinnow are commonly practiced.
In order to understand the need of citrus, we need first to understand it’s nutritious value. It is a rich source of vitamin C as well as pectin. It also contains fiber content, Folate and Potassium. Different diseases are being cured by it such as vitamin C cure scurvy, a disease caused by vitamin C deficiency. It also increases resistance against kidney stone and stomach cancer. Peel can be used for facial cleanser.
Different varieties are grown at different zones. It also depends upon its requirement. Cool season is responsible for its orange color. In areas where there is no winter the color remains green. Some varieties such as Persian Lime are sensitive to cool climate.
The above discussion is important but on the other hand citrus is also susceptible to many problems including pre-harvest and post-harvest diseases. Pre harvest losses include different disorders and diseases such as nutritional imbalance, respiratory disorder, temperature disorder, and chilling injury etc. However post harvest losses results in loss of quality and price. Different post harvest problems are explained below.
Due to different environmental factors such as high rain fall and warm climate for long time, citrus face different post-harvest diseases and disorders. Many bacteria and fungi attack on it. Most common pathogens and diseases are Green Mold, Blue Mold, black rot, anthracnose phomopsis stem-end rot diplodia stem-end rot. Different disorders include rind staining, oil spotting, and stem-end rind breakdown.
Green mold is caused by fungus named as Penicillium digitatum. Fungus enters the body from wounded areas. It rots the juice vesicles and its effect is commonly observed at 24°C. It can be controlled by storing citrus at 0°C to 1°C. Good ventilation is also required because ethylene enhance the activity of green mold.
Penicillium italicum is responsible blue mold. It also attacks the injured skin and initially watery spots occur. Its attack is at 24°C. It can be delayed by cooling just after packing. It also require ventilation.
Collectotrichum gleosporioides is responsible for anthracnose. It attacks on the injured part of fruit. It also increases growth of fungus. Brown spot are easily seen on its rind. It decays the fruit.
Stem end rot is due to Phomopsis citri. It is common on all varieties. Attack occur at flowering time and become dominant after several weeks of fruit harvest but don’t effect others fruits. To control, it must be treated with fungicide before harvest. Use of imazalil is recommended after harvesting and must be stored at low temperature.
Mechanical abrasion causes rind staining. Brown discoloration is easily seemed on the skin. It can be prevented in case if we apply gibberellic acid before harvesting.
With this in mind I conclude my discussion that the post harvest losses can be reduced but a lot of care including controlled temperature, storage condition and application of fungicide at proper time is required. This sheet provides the summery of handling of postharvest problems and care of cit rus for the grower to minimize their losses.
This article is collectively authored by Muhammad Umar, Syed Muhammad Zia-ul-Hassan, Waqas Ahmed Dogar
Institute of Horticultural Sciences, University of Agriculture, Faisalabad.