EMERGENCE AND GROWTH OF DURUM-WHEAT DERIVED FROM RED SMUDGE-INFECTED SEED

All durum wheat (Triticum turgidum L. var. durum Desf.) cultivars grow n in western Canada are susceptible to red smudge of kernels, caused b y Pyrenophora tritici-repentis (Died.) Drechs. This kernel discolorati on reduces commercial grade, but its effect on the health and developm ent of the crop when planted is unknown. Seedling emergence, plant gro wth, and grain yield were evaluated in held and controlled-environment studies using four cultivars that were established from seed which ha d 0, 50, or 100% infection. The 2-yr field study was conducted on a Sw inton loam soil (Aridic Haploborall). Infection resulted in a slower e mergence rate and decreased total seedling emergence id both held and controlled-environment studies. Poor seedling emergence resulted in sp arse stands, fewer spikes, less above-ground dry matter per unit area, and lower grain yield in the field. Seedlings from infected seed requ ired 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 inte rplant competition as a result of poorer emergence. We conclude that r ed smudge infection has the potential to reduce durum wheat grain yiel d, although the degree of reduction in a commercial crop will depend o n the level of seed infection and on the ability of the crop to compen sate for reduced stands. The latter will depend on plant vigor and the growing conditions associated with various seasonal environments.