Revealing the potential of elite coconut types through tissue culture
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Date
2006
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Abstract
Low income, smallholder coconut farmers have been facing difficulties for decades due to the falling price of copra, their traditional cash product from coconut. These farmers are now looking towards new, higher value products from coconut to make their industry viable over the longer term. There are a number of elite coconut types that have either a soft, jelly-like endosperm or a flavoursome, aromatic drinking water. They have a high commercial value in the confectionary and ice cream industries (soft endosperm types) or the soft drink market (aromatic types). The soft endosperm types (‘makapuno’) are naturally occurring mutants which cannot germinate in nature as their endosperm cannot support the germination of the embryo. They are known from a number of countries and are called makapuno (the Philippines, Vietnam and Thailand), kopyor (Indonesia), garuk (Papua New Guinea) or dikiri pol (Sri Lanka), depending on their origin. For propagation, the embryo has to be removed from the fruit and grown in vitro to produce a seedling. The aromatic types are also thought to be naturally occurring mutants which can only germinate in nature at a very low rate. They are known from a number of countries including Thailand and Vietnam. For propagation, the same kind of embryo culture procedure has to be used. The first attempt at the embryo culture of these mutant coconut types was by De Guzman in the Philippines in the early 1960s (for the makapuno coconut). Subsequent studies have led to the commercialisation of a technique so it is now possible to mass produce seedlings of the Filipino makapuno. Other countries are now attempting to use the same or modified embryo culture techniques to develop their own soft-endosperm or aromatic coconut production industries. The common problems these projects encounter are the low rate of conversion of the isolated embryos to plantlets and the duration of the protocol, which can be as long as 1 year. These issues ultimately lead to high production costs for the elite seedlings, well above that possible for subsistence farmers. However, a recent collaborative project funded by the Australian Centre for International Agricultural Research (ACIAR) has made some impressive improvements to the standard embryo culture protocol. These improvements include the use of a CO2-enrichment step within a photoautotrophic culture system and the application of plant regulators NAA or IBA to promote seedling rooting. By using this protocol on the embryos of normal coconuts the in-vitro stage can be reduced from 10–12 months to 3–4 months and the success rate in transferring embryos to seedlings in the field can be improved from about 50% to 100%. The new improved protocol now needs to be refined and applied to the different mutant coconut types that are found around the world.
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Keywords
elite coconut types, tissue culture, coconut
Citation
Proceedings of the International Coconut Forum held in Cairns, Australia, 22–24 November 2005. ACIAR Proceedings No. 125