INOCULATION OF SEEDS WITH BIPOLARIS-SOROKINIANA AND SOIL FUMIGATION METHODS TO DETERMINE WHEAT AND BARLEY TOLERANCE AND YIELD LOSSES CAUSEDBY COMMON ROOT-ROT

Wheat and barley plants that are severely infected with common root ro t yield less than uninfected ones. Resistant cultivars usually have fe wer diseased plants but some cultivars show tolerance as no yield loss occurs even though many plants display disease symptoms. This study a ssessed disease severity and yield loss due to common root rot in cult ivars of wheat and barley by two techniques: i) sowing infested seed i n soils with low inoculum levels of Bipolaris sorokiniana (Sacc. in So rok.) Shoem., and ii) planting healthy seed in soil treated with the f umigants, metam and basamid. Infested seed exhibited reduced emergence , increased disease severity, but plot yield was not significantly aff ected compared with uninfested seed. The average yield loss or gain fr om seed treatment amongst all selections of wheat and barley was not s ignificantly different. Losses were of the same magnitude (11.1% in ba rley, 6.2% in wheat) as reported in other studies. Soil fumigation red uced levels of B. sorokiniana in soil and disease severity. It also le d to increased nutrient levels in soil and plant tissues, plant height , and plot yields by 16-29% compared with untreated areas. Tolerance t o common root rot was exhibited by BW632, Virden, and Melvin. These lo sses are higher than reported in other studies which suggests yield lo ss may be underestimated or that common root rot is only one component of a root problem complex being affected by fumigants.