In applying biotechnology to agriculture, the principal areas involve manipulation of crop plants and manipulation of microbial or invertebrate associates of crop plants and weeds. Technological objectives may be achieved by conventional selection and breeding or by genetic engineering of plants, microbes, or invertebrates, or via manipulation of the environment. Such technologies can be combined in various agronomic systems with traditional practices such as chemical pesticides or fertilizers. Fungi play an expanding role in agribiotechnology as biological control agents, as mycorrhizal associates of plant roots, as agents for the degradation of lignocellulose and other forms of bioremediation (the application of microorganisms to biodegrade pollutants), or as food crops which utilize agricultural waste as a substrate. In food and beverage processing, fungi supply an array of enzymes plus natural flavor and color additives.