Immunity to rusts in wheat: theory, fact and practice

Immunity is an innate quality of wheat to avoid rust diseases. Non-host resistance (NHR) is a form of immunity present in distantly related species of wheat. Once the NHR is introgressed to the target species, it may confer immunity. Incorporation of rust resistance from alien or tertiary sources has been continuing for the last 115 years. There have been remarkable introgressions like 1BL.1RS in 1973 which revolutionized the wheat production worldwide. It was thought that this NHR will confer long-lasting immunity to rusts, however, myth was short-lived and the emergence of new, more aggressive and virulent pathotypes rendered varieties based on this type of resistance as susceptible. Therefore, it became very clear that wheat rusts can overcome even NHR through genetic changes in virulence. It emphasizes the role of modern tools and novel principles in the management of wheat rusts through durable rust resistance. CRISPR/Cas9 genome editing is a non-transgenic approach to have a new plant type conferring rust resistance. In addition, effectors or other chemical bases can also be explored as other tools for wheat rust management. Precise breeding with the support of marker assisted selection and genetic engineering to combat evolving pathogen genotypes is going to be at the forefront and becoming an integral part of wheat improvement programmes. However, the fact remains that wheat has to live with the rusts and these diseases have to be managed judiciously.