Influence of Nitrogen Supply on the Susceptibility of Wheat to Septoria tritici

Nitrogen (N) fertilization is required for achieving high yields in wheat (Triticum aestivum L.) but may enhance the development of Septoria tritici Rob. ex Desm. A study was undertaken to investigate how N supply influences the area under disease progress curve (AUDPC). Two field experiments were carried out in a typical argiudol in 1996 and 1997. Six cultivars were grown at two N treatments (0 and 100– 150 kg N/ha) in a split plot design. Percentage of necrosis (severity) of the two upper leaves of each treatment was evaluated three times during the growing season. Height and heading date were also scored and related to the resistance level. In 1996, with weather conditions conducive to the disease, AUDPC values were higher in the fertilized treatment. In 1997, with insufficient rain immediately after inoculation, the disease only progressed faster under N fertilization in the flag leaf, which was exposed to conducive environmental conditions from its appearance. The effect of N fertilization was influenced by the cultivar characteristics, climatic and agronomic conditions. Knowledge that N fertilization promotes the development of S. tritici in conducive conditions will be useful for deciding management strategies of the cultivars and for optimizing conditions for the selection in breeding programmes