Accurate quantitative assessment of the benefits accruing from the genetic improvement of crops is difficult. Crop yield increases are achieved through the introduction of new, improved varieties, through improvements in cultural practices and as a consequence of interactions that occur between new varieties, cultural practices and environmental conditions. Part of the yield increases from new varieties is as a consequence of genetic plant resistance to pests and diseases. Plant breeding, which is dependent on there being available a wide relevant genetic base for each crop, has also provided considerable improvements in quality, as well as improving adaptability to a wider range of environments.
In the developed world estimated annual yield increases from the genetic improvement of crops, especially cereals, are of the order of 1–2%. Examples are given from a number of crops of hybrid varieties, of varieties with improved quality and of varieties that are genetically resistant to pests and diseases to illustrate that conventional plant breeding, allied to multi-disciplinary, strategic research, has been very effective, both economically and in protecting the environment.