Disease resistance breeding in wheat: Theory and practices
288Globally a number of diseases affect wheat include three rusts, foliar blights, Fusarium head scab, the loose smut, flag smut, and powdery mildew. Genetic resistance is the most effective, least expensive, and environmentally safe means of rust diseases management. A large number of resistance genes originating from wheat and related species has been cataloged. The key points for the management of wheat diseases particularly rusts has always been to avoid large scale planting of single genotype/similar resistance and deploy varieties with diverse resistance, if possible then resistance based on more than one effective gene. The long-term success of breeding for disease resistance is influenced by three important factors: (a) the nature of pathogen and diversity of virulence, (b) availability and type of resistance, and (c) screening methodology and selection environment for tracking resistance. Diversity and durability of the resistance are two most important feature of the breeding for disease resistance in wheat. Resistance based on additive genes and gene complex providing resistance to multiple diseases have been successfully exploited by wheat breeders. CIMMYT’s spring wheat breeding program has carefully defined its target production environments into six mega-environments. DNA markers closely linked with resistance have been used successfully used by the concerted efforts from breeders, pathologists and molecular biologists for improving selection efficiency for disease resistance and other traits in wheat improvement programs.