Influence of Septoria tritici on Yield, Yield Components, and Test Weight of Wheat under Two Nitrogen Fertilization Conditions

ABSTRACT Nitrogen fertilization is required for achieving high yields in wheat (Triticum aestivum L.), but N may enhance the development of leaf blotch (Septoria tritici Roberge in Desmaz., teleomorph Mycosphaerella graminicola (Fuckel) J. Schröt. in Cohn). The present study was undertaken to investigate how Septoria leaf blotch affects yield, yield components, and test weight (TW) of different cultivars under different N supplies. Field experiments with six cultivars were carried out in a split‐split plot design during 1996 and 1997. Inoculation treatments were the main plots, N fertilization levels were the subplots, and cultivars were the sub‐subplots. Thousand‐kernel weight (TKW) was higher and TW lower in 1996 than in 1997. Interaction year × inoculation was not significant for any trait; year × fertilization was significant for yield and EPM2, and year × cultivar was significant for all traits except TKW. The separated analysis for each year indicated that additional N increased yield, EPM2, and KPE, but not TKW or TW. Inoculation with S tritici reduced yield and KPE, in both years and TKW, TW, and EPM2 in 1996. Differences between cultivars occurred for all traits except EPM2 in 1996. The percentage reduction in yield, yield components, and TW due to the inoculation was similar in fertilized and nonfertilized conditions, despite the increase in the area under disease progress curve (AUDPC) values by N fertilization in 1996. Cultivar differences in tolerance is suggested.