Barley Net Blotch Disease Management: A Review
Abstract
Barley (Hordeum vulgare L.)is one of the ancient grain crops cultivated and used worldwide. In Ethiopia, barley is among important staple crops next to tef, maize, wheat and sorghum mainly grown on about 1 million ha of land with average yield of 2.1t ha. It is the predominant cereal in the high altitudes and it accounts nearly 25% of the total production in Africa.
The fungi Pyrenophora teresf. teres (Ptt) and P. teresf. maculata (Ptm) cause net form net blotch (NFNB) and spot form net blotch (SFNB) of barley, respectively. Net blotch is one of the most important barley diseases which reduce both quality and quantity of barley grain. Yield loss due to this disease reaches up to 100% insusceptible cultivars under severe epidemics. In Ethiopia, barley net blotch is among widely distributed and destructive diseases in cool highland areas and yield losses reaching about 67% have been recorded. Currently, the disease can be controlled using different approaches such as cultural, chemical and biological controls as well as using resistant cultivars of which development and deployment of resistant cultivars is the best management method. However, it is argued that using integrated disease management is one of the most important strategies that should be followed to reduce the effect of barley net blotch diseases. This review discusses recent information on economic importance, epidemiology, life cycle, host range, geographical distribution and disease management of barley net blotch disease. It also presents the barley net blotch disease management methods such as cultural, chemical, biological and use of host resistance methods. Under host resistance method, information on types of resistance, sources of resistance have been presented.
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Introduction
Barley (Hordeum vulgare L.)is one of the most important crops grown worldwide at an altitude ranging from 1400 to 4000 meters above sea level (Zemede, 2002). At global level, barley ranks fourth among cereal crops in both yield and hectare coverage after wheat, rice and maize (Munck, 1981). In Ethiopia, barley grown from 1500 to 3500 meters above sea levels predominantly as food crops (Berhane, 1996) and ranks fifth after teff, maize, sorghum and wheat (Abdi, 2011).Barley is staple food for many people globally, especially for poor households, in addition to its uses in malting and as an animal feed (Newton et al., 2011). Barley grain is used for the preparation of different foodstuffs in Ethiopia, such as malt production, injera, porridge, roasted grains; and different local drinks and the straw and stem stub are good source of feed for animals and roof thatching, respectively, in Ethiopia (Fenta, 2018).
Barley productivity is low (1.97 t/ha) in Ethiopia as compared to world average of 3.1 t/ha and the reduction in productivity of the crop is mainly directed to multidimensional abiotic and biotic stresses (EIAR, 2019). In Ethiopia, net blotch is one of the most important barley diseases causing significant yield and quality loss (Yitbarek et al., 1996). Diseases such as scald, net blotch, spot blotch and rusts, can reduce yields by up to 67% (Chilot, 1998). Net blotch is one of the most widespread and a common foliar disease of barley, occurring in all barley-growing regions of the world (Weibull et al. 2003). This disease is of economic importance worldwide and can cause yield losses ranging from a trace to 100%, but typically cause losses from 10% to 40% (Mathre, 1997). The disease occurs in two forms, Pyrenophora teresf. sp. teres causes the net-form of net blotch (NTNB) and P. teresf. sp. maculata causes the spot-form of net blotch (STNB).
Conclusion
Net blotch of barley caused by the fungal pathogen Pyrenophora teres is a major foliar disease in major barley-growing regions throughout the world. It causes significant grain yield loss and reduces grain quality. Net blotch develops quickly when the environmental conditions are optimal including long periods of wet and cultural practice used.. It is the most important constraint that limits productivity of barley and results inconstantly low yield of barley in Ethiopia. The net blotch control provides a significant challenge now and in the future.
There are several methods to reduce yield losses due to barley net blotch disease. For example, crop rotation, fungicide application, and the deployment of resistant cultivars can be used to manage net blotch of barley. However, integrated disease management is one of the most important strategies that should be followed to reduce the effect of plant diseases in crops. A promising approach to achieve this aim while minimising use of pesticides is to apply and combine different agriculture practices that contribute to increasing crop yield by decreasing plant diseases directly or indirectly. For instance, combining good crop hygiene practices, the use of resistant cultivars and chemical control (both as seed dressing and foliar applications), is currently the most effective net blotch disease management strategy.
