Abstract
Net blotch, induced by the ascomycete Pyrenophora teres, has become among the most important disease of barley (Hordeum vulgare L.). Easily recognizable by brown reticulated stripes on the sensitive barley leaves, net blotch reduces the yield by up to 40% and decreases seed quality. The life cycle, the mode of dispersion and the development of the pathogen, allow a quick contamination of the host. Crop residues, seeds, and wild grass species are the inoculum sources to spread the disease. The interaction between the barley plant and the fungus is complex and involves physiological changes with the emergence of symptoms on barley and genetic changes including the modulation of different genes involved in the defense pathways. The genes of net blotch resistance have been identified and their localizations are distributed on seven barley chromosomes. Considering the importance of this disease, several management approaches have been performed to control net blotch. One of them is the use of beneficial bacteria colonizing the rhizosphere, collectively referred to as Plant Growth Promoting Rhizobacteria. Several studies have reported the protective role of these bacteria and their metabolites against potential pathogens. Based on the available data, we expose a comprehensive review of Pyrenophora teres including its morphology, interaction with the host plant and means of control.
Highlights
Net blotch caused by Pyrenophora teres Drechsler [anamorph Drechslera teres (Sacc.) Shoem] is a major foliar disease of barley (Hordeum vulgare L.) causing economic losses by reducing the grain quantity and quality
P. teres f. teres (Ptt) behaves as a necrotroph, while P. teres f. maculata (Ptm) acts as a hemibiotroph (Lightfoot and Able, 2010)
This review provides a reference point on net blotch of barley by highlighting P. teres severity, the changing complexity during the interaction between barley and P. teres and the management of net blotch control
Summary
Net blotch caused by Pyrenophora teres Drechsler [anamorph Drechslera teres (Sacc.) Shoem] is a major foliar disease of barley (Hordeum vulgare L.) causing economic losses by reducing the grain quantity and quality. Twenty-two hours post infection on a six row winter barley named Siberia, the first symptoms appear as brown necrotic spots on infected tissues increasing in size to form elliptical or fusiform lesions to 3 by 6 mm (Figure 2B; Keon and Hargreaves, 1983; Mclean et al, 2009). In addition to pyrenolines and pyrenolides, P. teres produces three other toxins, designated as N-(2-amino-2carboxyethyl) aspartic acid, anhydrospergillomarasmine A, and aspergilomarasmine A, symbolized by A, B, and C, respectively (Barrault et al, 1982; Friis et al, 1991) These peptides are thermostable with a low molecular weight and cause chlorosis, rather than the classical net blotch necrosis, after infiltration of the pure compound (Muria-Gonzalez et al, 2020). Once secondary infection is completed, P. teres colonizes the senescent tissues and produces pseudothecia on straw or weed residues (Figure 4; Liu et al, 2011)
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