Uneven Fruit Ripening (UFR); Wet Core and Tip Burn In Durian

"Uneven fruit ripening (UFR)" is one of the three common physiological disorders that occur in durian fruits. The others are "wet core" and "tip burn".

Physiological disorders cause abnormal development of the durian flesh and thus lowers the overall quality of the fruit. Usually there are no external symptoms on the outer husk and affected parts of the durian flesh can only be seen when the ripe fruit is opened. Affected parts are generally unpalatable.

Uneven fruit ripening (UFR)

Physiological disorders occur during the fruit growth and development stage. They are not caused by disease-bearing pathogens, insect pests, mechanical damage or storage conditions but are responses to unfavorable conditions such as tree health, water supply, or nutritional deficiencies

Uneven fruit ripening (UFR)  is characterized  by a hardened leathery aril, and a whitish color, odorless and tasteless pulp. It normally occurs when the fruits are about to ripen and remains invisible until the fruits are opened.

Wet core or water core makes the core at the centre of the fruit and the flesh of the fruit very moist and soft. Main cause is heavy rain just before harvesting. Other factors include a high water table during harvesting and low potassium in the soil. This disease occurs more often with young bearing trees.

Tip burn of durian occur when the tips of durian flesh turn dark brown. It usually occurs when there is rapid growth of the flesh, insufficient nutrients supplied, or insufficient water during the flesh formation. Tip burn usually occurs in young bearing trees, large fruits which are early maturing, and unhealthy trees.

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Here is a research article regarding uneven fruit ripening in durian:

Factors affecting uneven fruit ripening in 'Mon-Thong' durian  [2013] by

Pakcharoen, A.
Tisarum, R.
Siriphanich, J.

Abstract:
Uneven fruit ripening is often found in 'Mon-Thong' durian. This defect cannot be detected from external appearance and its cause is unknown. It has been suggested that harvesting too early and leaf flushing during fruit growth were perhaps the most probable causes of the problem. To evaluate whether maturity stages were related to uneven fruit ripening, 'Mon-Thong' durians were harvested at 106 and 113 days after anthesis (DAA). The 106 DAA fruits were found to have the higher score of uneven fruit ripening, as well as the higher variation in pulp firmness and soluble solids concentration compared to those harvested at 113 DAA. In addition, to determine whether competition for assimilates between the fruit and other developing parts, such as flushing leaves, was also related to uneven fruit ripening, bearing durian trees were shaded by 50%, using saran nets for 3 weeks during 92-112 DAA. It was found that the fruits from shaded trees, harvested at 113 DAA, had higher uneven fruit ripening characteristics than those from the control trees.

(Source: AGRIS FAO United Nations)

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Here is another article on how mulching can reduce the incidence of uneven fruit ripening as well as wet-core in the Philippines:

Mulching arrests uneven fruit ripening in durian, study reveals

January 28, 2015 AgriBusiness  No comments  

Quality and quantity are the keywords that put an industry ahead of its competitors. Though there is increased demand for durian (Durio Zibethinus) in the world markets – due largely to its rich and exotic taste – the country has been unable to tap this opportunity for export earnings as the local industry is hampered by limited production of high-quality durian.

durian fruitThe durian production industry has been incurring losses due largely to a physiological disorder appearing in the fruits. Known as uneven fruit ripening (UFR), this disease is characterized by a hardened leathery aril, and a whitish color, odorless and tasteless pulp. It normally occurs when the fruits are about to ripen and remains invisible until the fruits are opened.

Efforts have been made to arrest the occurrence of this disease. One such effort has been the initiation of the study on the “Uneven Fruit Ripening and other Physiological Disorder in Durian”by the Bureau of Plant Industry (BPI) and Davao National Crop Research and Development Center, with the support of the Bureau of Agricultural Research in the conduct of a study. The study aimed at determining the causal agents of UFR in durian fruits and controlling the occurrence of the said disease in maturing and ripening stage of durian.

Results of the study revealed that mulching significantly minimized the incidence of UFR and wet core in durian. Mulching is the principle of covering the soil surface of the plant’s base with materials such as rice straws and plastic sheets to reduce the infiltration rate of water into the soil and minimize the absorption of water into the roots. It was observed that the excessive water uptake by plant is the major cause of UFR and wet core. Wet core is somewhat similar to UFR by the fact that it affects the flesh or pulp of durian giving its pulp a watery and dull taste.

One significant observation obtained from the study is the amount of rain as the major causal agent of UFR in durian. It was concluded that high rainfall at 200 mm and above during maturity period of durian incurred the highest incidence of UFR and wet core. Results of the study showed that rainfall triggers the growth of shoots that compete for the nutrients needed by the fruit to attain full maturity and development.

Moreover, the study recommends to apply mulching using plastic sheets one month before maturity or harvesting especially during rainy season.

(Source: Business Diary.com.ph)

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A rotting durian fruit probably caused by of wet core (source : bas-sf.com)

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