Emergence and Growth of Durum Wheat Derived from Red Smudge‐Infected Seed

All durum wheat ( Triticum turgidum L. var. durum Desf.) cultivars grown in western Canada are susceptible to red smudge of kernels, caused by Pyrenophora tritici‐repentis (Died.) Drechs. This kernel discoloration reduces commercial grade, but its effect on the health and development of the crop when planted is unknown. Seedling emergence, plant growth, and grain yield were evaluated in field and controlled‐environment studies using four cultivars that were established from seed which had 0, 50, or 100% infection. The 2‐yr field study was conducted on a Swinton loam soil (Aridlc Haploborall). Infection resulted in a slower emergence rate and decreased total seedling emergence in both field and controlled‐environment studies. Poor seedling emergence resulted in sparse stands, fewer spikes, less above‐ground dry matter per unit area, and lower grain yield in the field. Seedlings from infected seed required significantly more time to head than those from non‐infected seed; however, plant growth and yield of growth chamber‐grown plants were not affected. Greater yield per plant derived from infected seed than from non‐infected seed in field studies was attributed to reduced interplant competition as a result of poorer emergence. We conclude that red smudge infection has the potential to reduce durum wheat grain yield, although the degree of reduction in a commercial crop will depend on the level of seed infection and on the ability of the crop to compensate for reduced stands. The latter will depend on plant vigor and the growing conditions associated with various seasonal environments.