THE EFFECT OF COMMON ROOT-ROT ON THE YIELD OF RESISTANT AND SUSCEPTIBLE WHEAT

The impact of common root rot, caused by Cochliobolus sativus, on the yield of mixtures of resistant and susceptible backcross-6 derivative lines of Neepawa and Chester wheat was examined in field tests at thre e locations between 1991 and 1994. Different blends consisting of all 25% incremental combinations of resistant and susceptible back cross l ines within each cultivar were evaluated for disease severity and yiel d at root rot nurseries and disease-free sites. Significant (P < 0.05) differences in yield were often detected among cultivars. However, wi thin cultivars, no consistent yield differences were observed among bl ends of resistant and susceptible lines of the same cultivar regardles s of root rot severity.