Advanced epidemiology of wheat stem rust: disease occurrence and progression

Abstract

An advanced insight into wheat stem rust progress curves is mainly needed by breeders and pathologists to improve accuracy and specificity of estimates of disease occurrence and development. It is necessary to identify certain disease curve elements for characterization of high variations in stem rust progress across different wheat cropping systems. A number of standard curves were fitted to a four-season data on stem rust severity to determine more predictive disease progress curve elements for wheat cultivars sown at different times. Exponential curve provided the best fitted parameters to be used as wheat stem rust progress curve elements. Sowing date and cultivar resistance significantly affected area under disease progress curve (AUDPC), maximum disease severity, and exponential parameter b. Mean AUDPC for early and late sowing dates were greater in susceptible cultivars (Bahar, Chamran II, Parsi and Sivand) than in resistant (Baharan and Pishtaz) and semi-resistant (Pishgam and Sirwan) cultivars. In semi-resistant cultivars, AUDPC increased by 37.44% at late sowings. Principal component analysis detected contributions of AUDPC, disease onset, maximum disease severity, and two exponential parameters in disease progression. This new understanding helps to achieve more accurate outcomes for future disease measurements for wheat breeding and wheat stem rust management programs.

Keywords

• black rust
• cereals
• epidemic
• multivariate analysis