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Lack of Relationship Between Susceptibility to Common Root Rot and Drought Tolerance Among Several Closely Related Wheat Lines

Common root rot caused by Bipolaris sorokiniana is a disease of wheat associated with plant stress. Three cultivars (Siouxland, TAM 200, and TAM 107) and several hard red winter wheat lines closely related to TAM 107, but known to differ with respect to drought tolerance, were included in a 2-year dryland field study to evaluate whether observed variation in drought tolerance was associated with susceptibility to B. sorokiniana. Untreated seed of each entry or seed treated with imazalil was planted in soil naturally infested with B. sorokiniana. Plants were evaluated at jointing and at harvest. Disease incidence and severity, number of plants, number of heads, and grain weight per meter were evaluated. Grain weight and number of heads of individual plants were recorded in order to correlate disease rating of each plant with yield components. Plot yield and test weight also were measured. There were significant entry by seed treatment interactions for number of heads per plant, grain weight per plant, and grain weight per meter. A year by treatment interaction was found for the jointing disease index, and plants grown from seed treated with imazalil had a significantly lower disease index than those grown from nontreated seed. Observed drought tolerance among the three varieties and eight closely related plant introductions was not associated with disease susceptibility to common root rot.