Structural characterization of stripe rust progress in wheat crops sown at different planting dates

An advanced insight into characterizing stripe rust progress curves is required to improve accuracy and efficiency of future research for disease measurement and estimation purposes. The rate of stripe rust increase in wheat crops is highly variable, resulting in variations and uncertainties in evaluating disease progress over time. This variability was described by fitting standard curves to disease severity data collected over a four-season experiment to identify effective disease curve elements in Iranian wheat cultivars planted at different dates. Gaussian curves appeared to be the best fitted models for all four growing seasons. Three Gaussian parameters in combination with the area under the disease progress curve (AUDPC), disease onset time, maximum disease incidence and severity were then considered to describe the rate of disease increase. Based on H-tests of Kruskal-Wallis one-way analysis of variance, cultivar and planting date significantly affected AUDPC, maximum disease incidence and severity. There were significant correlations between continuous disease descriptors. Then, significant associations were determined between AUDPC, disease onset time, Gaussian parameters, maximum disease incidence and severity according to factor analysis. With these novel findings, we should be aware of descriptive value of wheat-stripe-rust progress variables. Such information will assist with stripe rust measurements for wheat breeding programs, yield loss estimation, development of disease control strategy, and epidemiological studies.