Influence of Septoria tritici On Yield and Baking Quality of Wheat.

Leaf Blotch (LB) caused by the hemibiotrophic pathogen Septoria tritici causes reductions in grain yield and quality in wheat by affecting the photosynthetic active area of the crop. Reductions in photosynthesis rate may increase grain protein content (GPC) due to a dilution effect, influencing the baking quality of flour. On the other hand, Nitrogen (N) fertilization is required for achieving high yields in wheat but may enhance the development of LB, depending on the environment, cultivar and genotype-environment interaction. The aim of this study was to evaluate the effect of three nitrogen levels, fungicide applications, triazole-strobilurin and triazole-only, on LB severity, grain yield, GPC and rheological properties, in three different quality group cultivars. A field experiment was conducted in 2009 in a split-split plot design at Estación Experimental Julio Hirschhorn, Facultad de Ciencias Agrarias y Forestales, La Plata, Argentina. Fungicide treatments were the main plot, N fertilization levels were the sub-plots and cultivars were the sub-sub-plots. Severity, yield, GPC and alveogram-farinogram values were evaluated. Data were analyzed by ANOVA for split-split plot designs. Fungicides containing strobilurins caused the greatest reductions on disease severity. Severity reductions were found with increasing N levels. Grain yield increased when disease was controlled with strobilurins, and with the maximum N levels. GPC was higher when severity increases and with the maximum N levels. Regarding Alveogram values, tenacity (P) decreased with fungicides, especially with strobilurins. P value was higher in the best quality group (QG) cultivar. Extensibility (L) tended to increase with fungicides treatments, N levels and the best QG cultivar. Dough strength (W) was higher with high N doses and in the best QG cultivar. The P/L ratio showed significant differences among cultivars only; the better QG was, the better P/L values were.  Farinogram values, Water Absorption (A), Development Time (B) and Stability (D) were better in the best QG. Only Degree of Softening (E) showed significant Fu x Cu and Fe x Cu interactions.