Historical durability of resistance to wheat diseases
In Kansas, estimated annual losses from wheat diseases averaged 16 percent from 1976 through 1988; however, losses have declined to 10 percent in recent years. This decline is mainly due to emphasis on developing cultivars with resistance to important diseases.
Data from annual Kansas State University Extension publications were used to track disease ratings over time for individual wheat cultivars to eight diseases to draw inferences on the durability of deployed resistance. The duration of durability of resistance to leaf rust has been short for some cultivars but moderate for others. Conversely, the duration of durability of resistance to stem and stripe rusts has been long, although a recent virulence shift in the stripe rust pathogen indicates only moderate duration.
Duration of durability of resistance toward tan spot, Septoria tritici blotch, wheat soilborne mosaic, and wheat spindle streak mosaic has been long. Resistance to wheat streak mosaic has been of long duration in some cultivars but others have shown only moderate duration of durability.
The effort by breeders to produce cultivars with resistance to diseases in Kansas has resulted in an annual savings of about $58 million. Just as important as the incorporation of resistance into those cultivars is the moderate to long duration of durability of the resistance contributing to effective management of these diseases.