Grain quality in wheat—Impact of disease management

Abstract

Abstract Winter wheat is commonly attacked by a range of major leaf diseases like septoria tritici blotch (Zymoseptoria tritici) (STB), yellow rust (Puccinia striiformis) (YR) and powdery mildew (Blumeria graminis) (PM), which have significant negative impacts on yields. Fungicides can mitigate these yield reductions and stabilize yields, mainly by helping to maintain green leaf area during grain filling. Trial data collected in the period 2007–2017 were analysed for links between disease control, yields and impact on grain quality parameters. The fungicides applied in this study were typically appropriate rates of mixtures of fungicides belonging to azoles, strobilurins and SDHIs and data represent different fungicide strategies carried out in different varieties, seasons and localities. Yield correlated positively to grain quality parameters such as thousand grain weight (TGW), specific weight (TW) and grain starch content (GSC). A negative correlation between yield and grain protein content (GPC) was found, while a strong positive correlation was measured between GPC and grain gluten content (GGC). Yield also correlated to % STB severity and % green leaf area (GLA). Overall, fungicide control strategies increased grain yields, TGW, TW and GSC significantly compared to untreated. No significant differences were measured between these parameters for three different strategies using either one or two treatments or treatments according to a decision support system. When treated and untreated plots were compared, a small but still significant reduction of GPC from 10.5% in untreated to 10.2% in fungicide treated plots was measured. Specific trials investigating impact from three dose rates of fungicides showed that full rate increased yield, TGW, TW and GSC significantly compared with the 25% of standard rate, while no significant differences for untreated and the three tested dose rates could be measured for GPC, GGC or grain moisture content (GMC). In four specifically analysed varieties with similar yields, TGW, GPC, GSC, TW and GMC were genotype specific and varied significantly between the four analysed varieties. In 57 trials with severe attack of either STB, YR or PM fungicides provided similar yield responses. Control of all three diseases reduced the GPC significantly. Control of YR and PM were found to have similar impacts on GPC, while STB had a steeper negative impact on GPC.