ISHS Acta Horticulturae 222: Symposium on the Fertilization of Vegetables under Protected Cultivation
IMPROVING QUALITY OF LETTUCE BY BREEDING FOR LOW NITRATE CONTENT |
| Author: | K. Reinink |
| Abstract:
A high nitrate content in vegetables can be dangerous to human health. Breeding for low nitrate content plays an important role in the solution of this problem. A large genotypical variation has been found for nitrate content in lettuce. Genetic studies revealed that nitrate content in lettuce is a quantitative characteristic with mainly dominant genes controlling low nitrate content. Crosses between low nitrate cultivars have shown that a further reduction in nitrate content is possible by accumulation of genes for low nitrate content. The property of low or high nitrate accumulation is relatively stable over a wide range of soil nitrate contents, temperatures and light intensities. Selection can already be done in a young plant stage. Nitrate content in plants fluctuates strongly with time of day, but not all cultivars seem to respond in the same way to this factor. Also within different plant parts nitrate content can vary considerably. In recent years the physiology of nitrate accumulation in leafy vegetables has been elucidated to a large extent. Nitrate is mainly accumulated for osmotic purposes and is accumulated in the vacuole of the plant cell when photosynthesis is too low to provide enough organic solutes. No physiological explanation for the large genotypical variation has yet been given. Within a few years new lettuce cultivars for winter production with a substantially reduced nitrate content are expected. | |
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