The Department for Food and Rural Affairs (Defra) has granted approval for Rothamsted Research to extend a trial of genetically modified (GM) wheat this autumn.

The independent Advisory Committee of Releases to the Environment found that the trial will have no adverse effects on human health or the environment. Defra has set precautionary conditions to ensure no GM material will enter the food chain.

In 2011 Defra authorised Rothamsted Research in Hertfordshire to plant its GM aphid-resistant wheat in spring 2012 and 2013. The GM wheat produces a naturally occurring pheromone that not only repels aphids, but also attracts their natural enemies, such as ladybirds and wasps.

Currently, a significant proportion of the UK wheat crop is treated with chemical insecticides to control cereal aphids, which reduce yields by sucking sap from the plants and transmitting barley yellow dwarf virus.

Unfortunately, repeated use of such chemical sprays leads to aphids developing resistance to insecticides, while killing other beneficial species of insects and thereby damaging ecosystems.

Despite potential gains to be made by developing GM wheat with natural defence against aphids, Rothamsted was targeted by anti-GM activists last year. Defra said extending the trial will enable further data to be obtained on the performance of GM wheat later in the year, under different weather conditions and against different aphid populations.

A crop of spring-sown Cadenza GM wheat is being grown at the research centre. The autumn extension will be sown in mid-September and destroyed after 10-12 weeks in late November or December.

The Cumberland & Dumfriesshire Farmers' Mart had 45 prime cattle forward at their weekly sale in Dum-fries on Wednesday when bullocks sold to 254.5p and averaged 233p, while heifers peaked at 256.5p and levelled at 233p.

There were 36 OTM cattle presented in the rough ring when beef cows averaged 143.8p and dairy cows levelled at 108.3p.

The firm also sold 127 prime hoggs to a top of £90.50 per head and 180p per kg to average 169.5p, while 103 prime lambs peaked at £106 and 253p to level at 231.2p. The 228 cast sheep forward saw heavy ewes sell to £103.50 for Texels and average £65.24, while light ewes peaked at £41.50 for Blackfaces and levelled at £38.45.

United Auctions sold 72 store heifers at Stirling on Wednesday to a top of 240.7p and an average of 208p (+0.3p on the week), while 148 store bullocks peaked at 264.6p and levelled at 221.8p (-1,4p). Nineteen store bulls sold to 223.9p and averaged 199.1p.

In the rough ring, 109 cast cows averaged 139.3p.