Chemical composition and deoxynivalenol in wheat of Central- Southern Paraná: nitrogen fertilization in top dressing associated with Azospirillum brasilense

The impact of agricultural management practices on the quality of grain was evaluated in wheat (Triticum aestivum L. BRS Tangará) from the South Central region of Paraná State (Ponta Grossa) in the crop years of 2010 and 2011. The field trial was carried out in succession with soybean (2010) and corn (2011). The treatments included inoculation of seeds with Azospirillum brasilense and increasing levels of nitrogen application in top dressing (0, 30, 60, 90 and 120 kg ha-1). The experimental design was in randomized block, factorial 2 x 5 (inoculation x N levels), with four replications. The parameters evaluated were water activity, moisture, protein, and grain contamination by deoxynivalenol (DON). The data were subjected to analysis of variance, comparison of means by Tukey’s test (p<0.05) and regression for nitrogen levels. The inoculation of seeds with A. brasilense increased the protein content in grain in 2010 (+1.6%; 16.9 g 100g-1) and 2011 (+1.7%, 15.7 g 100g-1), independently of the nitrogen level (p<0.01). Levels of nitrogen in 2010 presented a positive linear response with protein content, increasing by 14.2% using non-inoculated seeds (p<0.01, R2=0.955) and 14.4% for those inoculated with A. brasilense (p<0.01, R2=0.906). However, in 2011 a quadratic response was observed between nitrogen levels and protein content (p<0.01, R2=0.99), with stabilization or reduction in protein content using high levels of nitrogen (?120 kg ha-1). The contamination by DON was greater using high levels of nitrogen (3574 ?g kg-1, 120 kg ha-1; non-inoculated seeds) in 2011, with a quadratic response between nitrogen levels and contamination of grains (p<0.05, R2=0.772). Furthermore, 37.5% of the samples presented contamination by DON higher than the maximum tolerated limit established by Brazilian legislation (2000 ?g kg-1; whole-wheat grain). The data demonstrates that proper management of nitrogen enhances intrinsic effects arising from plant breeding.