Resistance of European winter wheat cultivars to spot blotch at juvenile growth stages

A total of 99 modern European winter wheat cultivars and breeding lines were studied for resistance to four Bipolaris sorokiniana isolates, obtained from wheat straw and grain, under laboratory conditions using a detached leaf technique. The resistance was evaluated on a 0 to 100% scale, where the lowest percent represents the highest resistance. Four checks with known resistance levels were employed as references. The screening technique used revealed low resistance of the tested material when compared for percent of disease severity (DS), but considerably higher variability of resistance when compared for area under the disease progress curve (AUDPC) index. The accessions showed the AUDPC index to vary from 0.11-0.84, 0.11-0.75, 0.10-0.84, and 0.09-0.68, respectively, for the four isolates. The correlation between DS and AUDPC index was strong (r = 0.82-0.92, P<0.01) for the isolates. However, comparison among different isolates exhibited weak correlation (r = 0.30-0.50) between DS and AUDPC index. The most resistant accession with an AUDPC index of 0.101 had the DS of 17%, whereas the most susceptible ones with an AUDPC index of 0.837 had the DS of 100% on the 10th day of disease development. The cultivar BR8 (DS = 27.5%; AUDPC index = 0.123), referred to in literature as resistant, showed the highest resistance in our study, and the cultivar BH1146 (DS = 46.3%; AUDPC index = 0.248), referred to as moderately resistant, was among the most resistant. Accessions SW53114, Hadm.0272199, Campari, Hadm.06886-98, Sj03-6 and Solitär (DS 36.3 to 50.0% and AUDPC indices 0.162 to 0.283) possessed similar resistance levels to that of the cultivar BH1146. This suggests that screening a large number of accessions will enable selection of modern European winter wheat cultivars with useful spot blotch resistance.