Net blotch (Pyrenophora teres Drechsler): An increasingly significant threat to barley production

Abstract

Pyrenophora teres is a pathogen causing a net blotch disease in cultivated barley, which is present worldwide and can thus significantly reduce barley yields. This fungus also infects wild barley and other plants of the Hordeum genus, as well as barley grass, wheat, oats and plants from various genera, including Agropyron, Bromus, Elymus, Hordelymus and Stipa. Based on the symptoms it causes on the infected barley plants, the pathogen can be divided into two forms: P. teres f. teres, which causes net-like symptoms, and P. teres f. maculata, which causes blotchy symptoms. Infected seeds, stubble and plant debris, and volunteer and weed plants represent primary sources of pathogen inoculum. During the growing season, the pathogen enters a sexual stage, developing pseudothecia with asci and ascospores. This is followed by an asexual stage, during which conidiophores with conidia are formed. The conidial (anamorphic) stage is much more common, whereby conidia is a source of inoculum for secondary infection during the barley growing season. The first symptoms appear at the end of winter and the beginning of spring, often during the tilling phase. The most characteristic symptoms form on barley leaves. Frequently, symptoms of the net form can be mistaken for other diseases occurring on barley, making molecular analysis essential for accurate detection of P. teres, its forms, mating types and hybrids. Current net blotch control measures are based on the combined application of cultural, chemical and biological control methods and the selection of resistant varieties.