Rust control to achieve stable wheat production has been a challenge to crop scientists for over a century. The occurrence of large-scale epidemics, common in the first half of the 20th century, has decreased due to an improved understanding of disease epidemiology, the genetic basis of host-pathogen interactions, use of for diverse resistance genes, and the development of cultivars with rust resistance. The major, race-specific resistance genes (R-genes) continue to be utilized improperly to control rapidly evolving pathogens like wheat rusts, resulting in ?boom-and-bust? cycles requiring cultivar replacement, often shortly after release. Although it is well known that utilization of at least two effective R-genes in combination can enhance resistance durability, the strategy is rarely implemented in the correct way when breeding or releasing varieties because rust resistance is just one of the traits required for a successful variety. Adequate to high levels of durable resistance can also be achieved through pyramiding 4-5 minor, slow rusting, or partial, resistance genes (PR-genes) that confer inadequate resistance when present alone. Breeding strategies to utilize combinations of major R-genes or pyramided multiple PR-genes with other desirable traits must be a primary goal of breeding programs aimed at achieving long-term control of wheat rusts while ensuring stable food production gains and protecting the environment. Both strategies have pros and cons and success depends on the availability of diverse resistance in adapted genetic backgrounds along with greenhouse, field and/or molecular facilities for selection. Because it is naïve to believe that all breeding programs, whether public or private, will follow the best practice of utilizing effective major R-genes in combinations, breeding for multiple PR-gene based resistance is considered a superior strategy for achieving durable resistance.

Global Wheat Program

Text in English

INT0610

CIMMYT Staff Publications Collection