Genetically modified foods (GM foods), also known as genetically engineered foods (GE foods), or bioengineered foods are foods produced from organisms that have had changes introduced into their DNA using various methods of genetic engineering. Genetic engineering techniques allow for the introduction of new traits as well as greater control over traits when compared to previous methods, such as selective breeding and mutation breeding. The discovery of DNA and the improvement of genetic technology in the 20th century played a crucial role in the development of transgenic technology. In 1988, genetically modified microbial enzymes were first approved for use in food manufacture. Recombinant rennet was used in few countries in the 1990s. Commercial sale of genetically modified foods began in 1994, when Calgene first marketed its unsuccessful Flavr Savr delayed-ripening tomato. Most food modifications have primarily focused on cash crops in high demand by farmers such as soybean, maize/corn, canola, and cotton. Genetically modified crops have been engineered for resistance to pathogens and herbicides and for better nutrient profiles. The production of golden rice in 2000 marked a further improvement in the nutritional value of genetically modified food. GM livestock have been developed, although, , none were on the market. As of 2015, the AquAdvantage salmon was the only animal approved for commercial production, sale and consumption by the FDA. It is the first genetically modified animal to be approved for human consumption. Genes encoded for desired features, for instance an improved nutrient level, pesticide and herbicide resistances, and the possession of therapeutic substances, are often extracted and transferred to the target organisms, providing them with superior survival and production capacity. The improved utilization value usually gave consumers benefit in specific aspects. There is a scientific consensus that currently available food derived from GM crops poses no greater risk to human health than conventional food, but that each GM food needs to be tested on a case-by-case basis before introduction.