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| Unripe Jatropha fruits; each fruit contains 3 seeds with 30-35% oil |
The local population of tropical areas can provide for its own energy needs by the oil-rich seed of the Jatropha curcas tree. This can be achieved by improving the production of this – currently still wild - tree for inclusion in traditional and innovative cultivation systems. This would improve the market position. Research partners from Africa, Europe, South and Central America, and Asia are cooperating in this project.
Jatropha, also called purging nut tree in view of its toxic components, seems to be a wonder plant. The seeds of this tree contain much oil that is suitable for biodiesel production in which even the aviation industry has shown an interest. Moreover, the tree survives on soils on which hardy anything else will grow. This means that the thus produced biodiesel is not competing with the cultivation of edible crops.
Reality, unfortunately, is different. Making production financially attractive requires the plants to be grown closely together and this results in mutual competition. It then appears that also this wonder plant starts suffering from pests and diseases. Another fact is that higher production levels are only achieved on better soils and under proper care; this means that they are still competing with edible crops.
Testing cultivation systems
Our crop experts are now, together with foreign partners, investigating cultivation systems in which the trees are still producing good yields. Three cultivation methods are compared: monoculture, as hedges surrounding other fields, and as crop in between other crops. Good fertilisation and pruning methods need to be found as well. In the wild the tree ripens from bottom to top: when seeds at the bottom are ripe, the top is still flowering. Simultaneous ripening of the seeds would be more practical for harvesting purposes. Pruning will give the plant a more shrub-like shape.
DNA markers
Our breeders are at the same time – together with the foreign partners – attempting to develop varieties with a low disease susceptibility, a low toxicity, a high oil content, and a tolerance to compact cultivation. They have collected seeds from all over the world for this purpose and they are analysing these seeds for DNA markers corresponding with favourable or - conversely - unfavourable properties of the tree. And they are also developing a method to eliminate the toxic properties of the material remaining after oil extraction. This would make the pressed cake suitable as animal feed, which is now not the case. The breeders are also attempting to reduce the toxicity of the cake in a different way. Phorbol ester is one of the toxic substances. Some varieties do not contain this substance but these are less productive. These varieties are now being crossed with more productive varieties.
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