Influence of Leaf Diseases on Grain Yield and Yield Components in Winter Wheat

Leaf diseases’ influence the relationship between the yield and yield components of winter wheat (Triticum aestivum L.). Field experiments were conducted during 2003–2006 on a light loamy gleyic cambisoil in the central part of Lithuania to determine how leaf disease severity level affects grain yield and yield components. The area under disease progress curves (AUDPC), grain yield and yield components were analysed using the analysis of variance and correlations. Infected wheat straw was applied to initiate epidemics in all treatments. Three winter wheat cultivars: Hereward, Aron and Tauras differing in the level of resistance to leaf diseases were used in the experiments. In total, six treatments were established: (i) untreated control, (ii) powdery mildew control (pmc) + leaf diseases severity level 0%, (iii) pmc + leaf diseases severity level 1.0–5.0%, (iv) pmc + leaf diseases severity level 5.1–10.0%, (v) pmc + leaf diseases severity level 10.1–25.0%, (vi) pmc + leaf diseases severity level > 25.1%. Wheat in all treatments, except for the untreated control, was protected by morpholine and triazole fungicides. Yield and yield components were affected by leaf diseases in all the treated cultivars during all experimental years. Significant (p ≤ 0.01) medium and strong correlation coefficients were found between AUDPC and yield in all the treated cultivars under high pressure of leaf diseases in 2004.