Coconut cousins

Sunday 31 July 2011

DNA analysis shows coconuts have two different origins

imageCOCONUT trees are found across the world and it is said that they played a fundamental role in human migrations and the development of civilisations. So far, nobody has studied the genetic variability in the tree. Now a study of the DNA shows that coconuts have two well-defined and differentiated populations representing two separate locations of cultivation—the Pacific basin and the Indo-Atlantic Ocean basin.



The study used DNA regions that do not code for important traits, and where a lot of mutations go unchecked. Due to these mutations these regions called microsatellites can be regarded as “fingerprints” of the coconut. About 1,300 coconuts from different parts of the world were studied.

It was found that in the case of the Pacific group, the coconuts were likely to have been first cultivated in Southeast Asia—the Philippines, Malaysia, Indonesia. In the case of the Indo-Atlantic Ocean basin group, the likely centre of first cultivation was the southern periphery of India, including Sri Lanka, the Maldives, and the Laccadives.

One exception to the general Pacific-Indian Ocean split is the western Indian Ocean, specifically Madagascar and the Comoros Islands, where the coconuts show a genetic mixture of the Indian Ocean type and the Pacific type. The study was published in the June 22 issue of PLoS One.

Currently, coconut trees around the world are suffering from a lethal yellowing, phytoplasma infection. Knowledge of the genetic structure may prove useful in targeting source populations for disease resistance and other crop improvement traits, authors say.

“Presence of the disease threatens the economies of developing countries as they will not be able to produce adequate quantities of copra for oil for local consumption as well as export,” says Bee F Gunn, lead author. As the demand for coconut oil increases it will also become unaffordable for people who use it daily, he adds.

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