Science - June 8, 2006

Super-healthy lettuce can be bred

The idea of using breeding techniques to make tastier tomatoes or lettuce with more health-promoting substances is less utopian than researchers thought. The biochemical composition of a plant is strongly determined by its genetic makeup. This discovery by plant scientists in Wageningen and Groningen was published online 4 June in Nature Genetics.

‘A plant easily makes thousands of metabolites. Which ones and how much is produced is often a result of environmental factors. A plant that gets too little light or undergoes another form of stress produces different substances. Research has now shown that for about 75 per cent of the metabolites we can now identify the genetic component upon which the genetic variation is based. That means there is a genetic base present upon which you can select desired substances,’ says Joost Keurentjes, a researcher at the Laboratories of Genetics and Plant Physiology, and first author of the article. Researchers at Rikilt and Plant Research International, and bio-informatics scientists at the University of Groningen co-authored the article.

‘We used Arabidopsis, which is a model plant, but the technique can be used for other plants. If you want sweeter tomatoes you don’t have to grow them in southern Europe, but you can breed a tomato that will grow in Dutch greenhouses. In principle the same applies for other organisms, such as substances you may want present in cow’s milk,’ says Keurentjes.

To determine the genetic base to metabolites the researchers chose a ‘blind approach’. ‘We don’t start by isolating one metabolite first, but take the whole mixture, which contains hundreds of them. Thanks to developments in analytical techniques we get a pattern of peaks, in which each peak represents an unknown metabolite. It’s not easy to identify these, but our colleagues in Groningen have written software to help us. With this we can determine which metabolites are probably regulated by the same genes, whether we have identified them or not,’ explains Keurentjes.

One of their findings is that there are about 700 metabolites in Arabidopsis from just one origin. Keurentjes: ‘That means that an Arabidopsis from Poland contains very different metabolites from an Arabidopsis in the Cape Verde Islands. Sometimes parent plants cannot manufacture a certain substance, because each is missing part of a chemical pathway, but the descendants can because they do possess the complete genetic information required.’ Because the metabolites can be derived from certain signposts on the DNA for qualitative traits, the QTLs, breeders can select for them, already at the germination stage. According to Keurentjes, these results fit well with the current trends in plant breeding, where there is increasing interest in taste and health-promoting substances. / GvM

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