Using genetic diversity for disease resistance in agricultural production

The three main germplasm resource bases used for genetic diversity in disease resistance are commercial varieties, landraces and wild ancestral species. Cultivar mixtures with landraces have traditionally been used by subsistence farmers to keep disease epidemics at low levels. These subsistence farmers Live mainly in developing countries and produce up to 20% of the world's food. Landraces have been a valuable source of disease resistance to them because of their already high adaptations in appropriate agronomic backgrounds. Mixtures with improved varieties are now being advocated as an alternative strategy for disease control in many crops. Wild germplasm are also being used to transfer new and valuable genes of disease resistance to cultivated crops. Continuous efforts are being directed at broadening the genetic base of crops by a search for sources of disease resistance, which remain the most practical and environmentally sound means for the control of most major diseases in agricultural crops.