Spot blotch resistance in derivatives of European winter wheat

Authors: ZILVINAS LIATUKAS, VYTAUTAS RUZGAS

Abstract: The effects of inoculum concentrations and the aggressiveness of spot blotch (Bipolaris sorokiniana (Sacc.) Shoemaker) isolates were evaluated on the resistance of 123 winter wheat advanced breeding lines developed from European winter wheat as well as on 3 control cultivars, BR8, BH1146, and Zentos. The test was conducted under laboratory conditions using a detached leaf technique. A total of 3 inoculum concentrations were used: 0.5 × 10^3, 1 × 10^3, and 5 × 10^3 spores mL^{-1}. The results of the study revealed low resistance of the tested material when accessions were compared by the percentage of disease severity (DS), but considerably higher variability of resistance was determined when the area under the disease progress curve (AUDPC) was used for comparison. The correlations between DS and AUDPC across inoculum concentrations varied from medium to high (r = 0.559*-0.909**; *P < 0.05, **P < 0.01) for isolates with higher aggressiveness, whereas it was high (r = 0.785**-0.939**) for those with lower aggressiveness. The correlations between DS and AUDPC across isolates were high (r = 0.769**-0.939**) for lower inoculum concentrations of 0.5 × 10^3 and 1 × 10^3, whereas they varied from medium to high (r = 0.559*-0.785**) for the highest spore concentration, 5 × 10^3. All of the concentrations can be successfully used for the evaluation of resistance considering DS development and the subsequent differentiation of accessions. However, the lower inoculum concentrations provided a higher differentiation of the accessions tested. Cultivar BR8, described in the literature as being resistant, exhibited the highest resistance among the accessions tested for AUDPC and DS, with results of 77.5 and 30.5%, respectively. Cultivar BH1146, referred to in the literature as having medium resistance, was evaluated by DS at 44.2% and by AUDPC at 146.4. About 23% of the accessions tested possessed the same resistance level as BH1146, or higher. Cultivars Dream, Aspirant, and Biscay were the most common among the ancestry of the most resistant lines. This suggests that it may be possible to select modern European winter wheat cultivars with sufficient spot blotch resistance when large numbers of accessions are screened.

Keywords: Bipolaris sorokiniana, inoculum concentration, resistance, winter wheat

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