Effect of leaf spot severity on yield and quality of durum wheat

Abstract

Leaf spots in wheat (Triticum aestivum L.) are important in Saskatchewan even under dry conditions (Fernandez et al., 2002). Durum wheat (T. turgidum L. var. durum) cultivars presently grown in western Canada are susceptible to leaf spots. The most common leaf spotting disease in durum wheat is tan spot [Pyrenophora tritici-repentis (Died.) Drechs. (anamorph Drechslera triticirepentis (Died.) Shoemaker)] Leaf spots are believed to cause reductions in yield and quality. The most widely used approach to measure the effect of leaf diseases on yield and its components has been the use of fungicides (Duczek and Jones-Flory, 1994; Eyal, 1972; Hosford and Busch, 1974; Rees and Platz, 1983). Inconsistent results with fungicide use in wheat were also reported (Bailey et al., 1992; Stover et al., 1996; Wang et al., 2002). In some cases, fungicide effects were not directly related to the occurrence of disease (Fehrmann et al., 1978; Wang et al., 2002), which makes them an unreliable tool to assess the effect of leaf spots on plant growth. To accurately quantify the negative effects of leaf spots on yield and quality, an approach other than disease control by fungicide application is necessary. The objective of this study was to evaluate the use of genotypes near-isogenic for leaf spot reaction to quantify the effect of leaf spots on grain yield and quality of durum wheat.