Infestation of soft spring wheat by leaf diseases depending on nitrogen nutrition

Abstract

Infestation of soft spring wheat plants depends on the growth stage and weather conditions of the growing season. Plants have the highest resistance to brown rust in the tillering stage. Brown rust developed in 2014 throughout the growing season. The lowest infestation intensity was during tillering – booting stage, which did not change from the experiment variant – 5.0 %. The lowest spread of brown rust was in the tillering stage – 10 %, in the booting stage – 40 %. The resistance was assessed 8 points. In the earing stage, the infestation intensity increased in no fertilizer variants and P30K30 to 8.0–8.2 % or by 60 % with a resistance of 7 points. This indicator in the variants with nitrogen fertilizers was 4.1–4.3 % with a resistance of 8 points, but all stems were infected (100 % spread). Affected leaves were in the middle layer, as their resistance by E. E. Saari and J. M. Prescott scale was at 5 points. Plants had the least resistance to brown rust in the milk stage of soft spring wheat grain. The intensity increased to 15.2–18.7 % or 2.1–4.7 times compared to the earing stage. The lowest resistance was assessed 6 points. All leaves were affected (resistance by E. E. Saari and J. M. Prescott scale – 1 point). In 2015, brown rust appeared in the milk stage of soft spring wheat grain. However, the infestation intensity was insignifcant – 5.0–6.5 % depending on the experiment variant. The prevalence of brown rust decreased from 60 % in unfertilized areas to 30 % on phosphorus–potassium background and up to 10 % with nitrogen fertilizers. Plant resistance was high – 7–8 points depending on the experiment variant. Powdery mildew develops throughout the growing season of both research years. In 2014, the infestation intensity is the lowest in the tillering stage – 7.7–8.0 % with 50 % spread, with the resistance of 7 points. In the booting stage of plants, the infestation intensity increased to 44.1–46.8 % or 5.8–5.9 times compared to the tillering stage. All plants were affected, and the resistance was 3 points. In subsequent stages of growth, the intensity of powdery mildew increased. Thus, in the earing stage this indicator increased to 65.1–69.2 % or 8.5–8.7 times, and in the milk stage – 9.5–9.7 times compared to tillering depending on the fertilizer. The stems of soft spring wheat were all affected, and the resistance was 2 points. Key words: brown leaf rust, powdery mildew, infestation intensity, spread, resistance.