A new trend in plant protection consists in the integration of biological and chemical control treatments. Unfortunately, the biological control agents for winter wheat are still in short supply. Bacteria of the genus Sphingomonas have a unique ability to produce prolyl endopeptidases. Those enzymes are capable of hydrolyzing the peptide PQPQLPYPQPQLP. During the growing season, the bacteria may be used to protect winter wheat against infections caused by fungi of the genera Fusarium. The objective of this study was to evaluate the effectiveness of bacterial isolates in protecting field-grown winter wheat plants against spike infections and to assess the effect of bacteria on the chemical composition and microbiological purity of winter wheat grain. The effects of bacteria of the genus Sphingomonas as biological control agents against Fusarium head blight (FHB) of winter wheat were evaluated in a three-year field experiment. For comparative purposes, the fungicides propiconazole at the elongation stage (BBCH 31) and fluoxastrobin + prothiconazole at the heading stage (BBCH 55) were applied. In 2010 and 2011, the application of cell suspensions of bacteria alleviated the symptoms of disease by 27.3% and 75.8%, respectively in comparison with control. Wheat grain yield was higher in plots subjected to the biological and chemical treatment (by an average of 9.5 and 13.6%, respectively). For the first time, we observed that biological control modified the chemical characteristics of wheat grain. In control grain, the content of gluten proteins was 7.9% higher than in grain treated with the biocontrol agent. In wheat grain treated with the biocontrol agent, the highest decrease was observed in the concentrations of alpha/beta-gliadins (10.59%), but grain quality was most affected by an estimated 8% decrease in the content of HMW glutenins. Biological treatment inhibited the growth pathogens of F. culmorum, F. poae, F. sporotrichiodes and F. avenaceum. A cell suspension of bacteria did not inhibit the growth of yeasts and epiphytic bacteria of the genus Azotobacter on grains.

22.4.2017