Breadmaking quality and yield response to the green leaf area duration caused by fluxapyroxad under three nitrogen rates in wheat affected with tan spot

Tan spot caused by the necrotroph pathogen Pyrenophora tritici-repentis (Died.) Drechs. [anamorph Drechslera tritici-repentis) (Died.) Shoem] causes reductions in yield and grain quality of wheat (Triticum aestivum L.) by affecting the photosynthetically active area of the crop which could affect grain protein content (GPC) and breadmaking parameters. Nitrogen (N) fertilization is required for achieving high yields and quality in wheat but can exert a profound effect on disease development and fungicide efficacy. The active ingredient fluxapyroxad, belonging to the carboxamides chemical group, not only control fungal pathogens and reduce disease progression but also, might increase green leaf area duration of the crop. We evaluated the effect of fungicide applications containing a carboxamide, in a mixture with triazole and strobilurin (TSC), above a double-mixture (triazole and strobilurin) (TS) under three N rates, on tan spot severity, healthy area duration (HAD), flag leaf healthy area duration (FLHAD) and grain yield. We also assessed its impact on GPC, wet gluten content, loaf volume and dough rheological parameters in wheat. Two field experiments were conducted during 2014 and 2015 in a split-split plot design with three fungicide treatments as main plots and three N fertilization rates as sub-plots using a susceptible cultivar (Baguette 11, Nidera). Treatment TSC significantly reduced the area under disease progress curve (AUDPC) and this was associated with increased HAD and FLHAD resulting in higher yields when compared to the TS treatment and the untreated control. The AUDPC values were lower with higher N rates in the untreated plots. The GPC and wet gluten content increased in untreated plots under 0 kg N ha−1 and 70 kg N ha−1 rate and was reduced following fungicide applications, however, this was reverted with the maximum N rate (140 kg N ha−1). Increases in GPC and wet gluten content in the untreated plots did not improve loaf volume and breadmaking parameters of wheat which only enhanced following fungicide application and N fertilization.