Engineering rice that needs less fertiliser

Genetic modification (GM) of crops is one of the more recent technological advances in agriculture designed to meet increasing demand for food. New research reveals that rice can be modified to use nitrogen more efficiently, thus reducing the need for nitrogen fertilisers while increasing yields.

The Food and Agriculture Organization of the United Nations (FAO) has estimated that food production must double by 2050 to feed an anticipated population of 9 billion1. Increased agricultural yields, if adequately managed and distributed, could contribute to ensuring food security. Technologies in use which increase yield include improved seeds, better irrigation and chemical fertilisers. However, the increased global use of nitrogen-based fertilisers over recent decades, from 3.5 million metric tonnes (Mt) in 1960 to 87 million Mt in 2000, has had a negative impact on the environment.

Nitrogen is quantitatively the most essential nutrient for plants and a major factor limiting crop productivity. However, excess nitrogen that is not taken up by plants can leach into waterways where it can trigger algal blooms and lead to eutrophication, where oxygen levels are greatly reduced in the water. It is also released into the atmosphere as nitrous oxide, a potent greenhouse gas.

To reduce the quantity of nitrogen fertiliser used in rice fields, researchers have genetically modified rice to improve its Nitrogen Use Efficiency (NUE). This was achieved by transferring a gene, which plays a key role in nitrogen uptake by plant roots, from barley to rice plants.

The researchers observed that the GM rice plant roots had more 'branches' than non-GM plant roots. This increases the surface area and increases nitrogen uptake. They also demonstrated that NUE increased by 36-61 per cent in plants containing the transgene. There was also a significant increase in key amino acids, such as glutamine, glutamic acid and asparagine, thought to play important roles in increasing nitrogen transportation and improving grain size.

Research is ongoing in the field of plant development, both through GM technology and through conventional breeding. Improving plant NUE could reduce both the costs of nitrogen fertilisers and the input of nitrogen into the environment. However, all GM products must be thoroughly assessed in accordance with the relevant legislation in order to ensure their safety to non-target organisms and the environment. Greater public acceptance of GM crops in Europe would also be required.

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