Inoculation of seeds with Bipolaris sorokiniana and soil fumigation methods to determine wheat and barley tolerance and yield losses caused by common root rot

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Wheat and barley plants that are severely infected with common root rot yield less than uninfected ones. Resistant cultivars usually have fewer diseased plants but some cultivars show tolerance as no yield loss occurs even though many plants display disease symptoms. This study assessed disease severity and yield loss due to common root rot in cultivars of wheat and barley by two techniques: i) sowing infested seed in soils with low inoculum levels of Bipolaris sorokiniana (Sacc. in Sorok.) Shoem., and ii) planting healthy seed in soil treated with the fumigants, metam and basamid. Infested seed exhibited reduced emergence, increased disease severity, but plot yield was not significantly affected compared with uninfested seed. The average yield loss or gain from seed treatment amongst all selections of wheat and barley was not significantly different. Losses were of the same magnitude (11.1% in barley, 6.2% in wheat) as reported in other studies. Soil fumigation reduced levels of B. sorokiniana in soil and disease severity. It also led to increased nutrient levels in soil and plant tissues, plant height, and plot yields by 16–29% compared with untreated areas. Tolerance to common root rot was exhibited by BW632, Virden, and Melvin. These losses are higher than reported in other studies which suggests yield loss may be underestimated or that common root rot is only one component of a root problem complex being affected by fumigants. Key words: Common root rot, loss, tolerance, seed inoculation, fumigation