Influence of Cultivar Resistance, Powdery Mildew, Planting Date, and Weather on Wheat Maturity and Yield

Background and Objective: Powdery mildew threatens wheat production worldwide. Cultivar maturity in interaction with climate, planting date, powdery mildew and production is little understood. Association of wheat maturity with powdery mildew, date of planting, wheat resistance and weather were observed in this study during four growing seasons. Materials and Methods: The H-test, correlation and Principal Component Analysis (PCA) characterized maturity time of eight commercial wheat cultivars planted at different dates during four growing seasons in Western Iran, Kermanshah. For H-test and correlations, a significance level was considered at 5%. The PCA confirmed H-test and correlation results. Results: Early maturing cultivars showed 12% earlier disease onset, 17% lower area under powdery mildew progress curve (AUPMPC), less severe disease, greater yield compared to late maturity. An early disease onset corresponded with a 33% longer maturation period at field scale. Early planting in October was associated with a 182% shorter maturity ranking in comparison with the optimum date in November. Ranking of maturation increased by 117% as planting was delayed from the optimum date to very late plantings in January. Correlations were significant between maturity period and disease onset, AUPMPC, exponential parameter r, maximum disease severity, average minimum temperature, rainy days, and wind speed in spring, and yield. Conclusion: This study provided a systematic understanding of the complex interaction of wheat maturity with powdery mildew, planting date, cultivar resistance, weather and yield that is required for a sustainable agriculture.