Effects of Net Blotch (Pyrenophora teres) on Malt Barley Yield and Grain Quality at Holeta, Central Ethiopia

arley (Hordeum vulgare L.) production is constrained by diseases such as net blotch caused by Pyrenophora teres Drechsl. The objectives of this study were to assess the effects of net blotch disease on malt barley yield and grain quality under natural infection. Four malt barley varieties (Beka, HB 120, HB 52 and Holker), three fungicide (propiconazole) spray intervals (at 7, 14 and 21 day) and no spray control were arranged in a randomized complete block design in four replications. The experiment was conducted at Holeta Agricultural Research Center, Ethiopia in the summer of 2005, on a plot of 12 m2 for each treatment. Disease incidence and severity, yield and grain quality parameters were measured and analyzed. The results indicated a significant (P< 0.05) difference in disease incidence and percentage severity index at 107 days after planting and for the Area under the Disease Progress Curve among spray intervals and the varieties. Variation in yield and yield components were indicated among the varieties. Relative yield losses of 7.711.5% occurred in Beka and 15.321.2% in HB 120. The hectoliter weight (HLW) for both the varieties and the spray intervals ranged from 63.5 to 66.8 kg and were significantly different among the spray intervals and the varieties. The varieties had thousand-kernel weight (TKW) in the range of 32.5 to 46.4 g. Net blotch severity reduced yield and TKW in Beka and HB 120. However, in other grain quality factors analyzed, significant variations were observed only mong the varieties. On slotted sieve screens (mm): 2.8, 2.5, 2.8 + 2.5, 2.2 and < 2.2 the % grain mass retained ranged from 30.647.3, 40.650.6, 74.792.3, 6.618.8 and 1.05.7, respectively. The grain protein content (GPC) of the varieties ranged from 8.49.5%. The germination- capacity varied from 99.1 to 99.8% and germination energy from 98.5 to 99.4%. The study showed that the grain plumpness, GPC and germination characteristics of the varieties meet the malt and brewery industry requirements. However, HB 120 and HB 52 appeared superior to Beka and Holker.