FOLIAR DISEASES AND NITROGEN AFFECT BREAD MAKING QUALITY IN WHEAT

SCHALAMUK S., SERRAGO, R. , CARRETERO, R. , TINGHITELLA, G. , CASTRO, E. AND MIRALLES, D.J

Rosario Sta Fe

Congreso; ICC International Conferences on Cereals and Cereal Products quality and safety; 2007

ICC

Foliar diseases, as Septoria blotch (Septoria tritici), Tan spot (Drechslera tritici repentis) and leaf rust (Puccinia triticina), reduce the economic value by decreasing both grain yield and quality (Dimmock and Gooding, 2002). To evaluate the effect of foliar diseases on industrial and bread-making quality parameters in wheat, different field experiments using the same genotype (cv Klein Pegaso) were carried out in four contrasting growing seasons (including different years and locations):  Arrecifes 2002, Buenos Aires 2002 (both with high nitrogen availability), and Buenos Aires 2005 with two different fertilization rates (N0-low and N1 high nitrogen availability, respectively). In all cases two fungicides treatments (i.e. protected with fungicides during the whole crop cycle and unprotected without fungicides applications) were applied. The severity of the diseases (mainly leaf rust) was particularly high in the unprotected treatments of Arrecifes 2002 and N fertilized plots of Buenos Aires 2005. In those conditions, fungicides increased grain weight and test weight. Grain protein was increased by fungicides in Buenos Aires 2005 N1, but not in Arrecifes. However, grain protein content expressed in absolute terms (mg of protein per grain) was higher when fungicide was applied in both situations, evidencing a “dilution” effect in Arrecifes through an increase in grain weight that masked the increases in nitrogen content into the grains. Protein (%) and dry gluten were highly associated in all the situations evaluated (R2=0.89), and both parameters were positively correlated with alveograph-W and L, and negatively associated with the P/L ratio. Nitrogen fertilization in Buenos Aires 2005 decreased the P/L alveograph ratio, from 1.22 in N0 to 0.6 in N1. The loaf volume of bread was positively correlated with P/L ratio, with higher bread volumes when crop was unfertilized and treated with fungicide. The structure of the crumb porosity, assessed by image analysis after scanning the loaves (Crowley et al., 2000), changed with N fertilization. Nitrogen fertilization increased porous area and the size of gas cells, however, the porous area was not related with bread volume. In summary, we observed large variations in grain quality parameters for the same genotype, and high levels of leaf rust severity determined reductions in grain protein, grain weight and test weight affecting the rheological properties of the dough.