Domestication of crops started some 11,000 years ago and since then much progress has been made. Since the rediscovery of Mendel’s laws early in the 20th century, the improved varieties planted by farmers worldwide have increasingly been developed by well-trained plant breeders, in contrast to farmer-developed varieties of previous eras. The high yielding varieties of the green revolution transformed agriculture in many developing countries, providing an opportunity for farmers to improve crop harvests and livelihoods. The utilization of plant breeding methodologies has led to the development of improved varieties.
Plant breeding has made an enormous contribution to global agriculture (yield, resistance to biotic stress, tolerance to abiotic stress, harvest security, improvement of quality traits including nutritional value, etc.). Yield in many crops has increased from 1 to 3 per cent per year. A large proportion (50 to 90 per cent) is due to improved varieties, rather than to other input factors, and in certain crops this percentage is increasing. The efforts of plant breeders have led to varieties with increased resistance to biotic stress, saving many millions of dollars in crop protection products per year, as well as to varieties with increased tolerance to abiotic stress, such as drought, salinity, flooding or herbicides.