EFFECTS OF NITROGEN FORMS AND RATES ON Fusarium culmorum GROWTH, FITNESS, AGGRESSIVENESS AND WHEAT, BARLEY AND TRITICALE RESISTANCE TO CROWN ROT DISEASE

Management of wheat crown rot disease relies mostly on cultural techniques. However, nitrogen’s effect on host susceptibility and Fusarium culmorum is not fully examined. Therefore, a series of experiments dealt with rates of nitrogenous fertilizers effect on pathogen fitness and varietal resistance of some small grain cereals. These experiments served as frameworks to examine the patterns of varietal defense against the causal agent. Nitrogen rates were studied for their effect on fungus growth under two temperatures, and on aggressiveness and disease resistance. This research adopted data mining analysis of experimental data to describe and model varietal resistance. The form and rates of nitrogen fertilizers significantly affected fungus growth, aggressiveness and varietal resistance. Forms of nitrogen use at (24 g/L) greatly biased disease resistance, and urea increased Fusarium culmorum fitness and aggressiveness, especially at 20-25°C. However, a reasonable nitrogen fertilization based on ammonium nitrate reduced these characteristics, resulting in a subsequently decrease in disease severity and a reliable expression of disease resistance. Integration of decision tree analysis and the methodology developed herein for selecting small grain germplasm should enable breeders to improve resistance to F. culmorum. Furthermore, to bring this disease under control, the use of ammonium nitrate as top dressing fertilizer in disease prone semi-arid regions are highly recommended.