Characterization of the Barley Net Blotch Pathosystem at the Center of Origin of Host and Pathogen

Abstract

Net blotch (NB) is a major disease of barley caused by the fungus Pyrenophora teres f. teres (Ptt), and P. teres f. maculata (Ptm). Ptt and Ptm infect the cultivated crop (Hordeum vulgare) and its wild relatives (H. vulgare ssp. spontaneum and H. murinum ssp. glaucum). The main goal of this research was to study the NB-causing pathogen in the crop center of origin. To address this, we have constructed a Ptt (n = 15) and Ptm (n = 12) collection isolated from three barley species across Israel. Isolates were characterized genetically and phenotypically. Aggressiveness of the isolates was determined based on necrotrophic growth rate on detached leaves of barley. In addition, isolates were genetically characterized by the mating type, followed by phylogenetic analysis, clustering them into seven groups. The analysis showed no significant differentiation of isolates based on either geographic origin, host of origin or form (Ptt vs. Ptm). Nevertheless, there was a significant difference in aggressiveness among the isolates regardless of host species, geographic location or sampling site. Moreover, it was apparent that the isolates derived from wild hosts were more variable in their necrotrophic growth rate, compared to isolates sampled from cultivated hosts, thereby suggesting that NB plays a major role in epidemiology at the center of barley origin where most of the diversity lies. Ptm has significantly higher necrotrophic and saprotrophic growth rates than Ptt, and for both a significant negative correlation was found between light intensity exposure and growth rates.

Pyrenophora teres: Taxonomy, Morphology, Interaction With Barley, and Mode of Control

“…Thus, Ptt behaves as a necrotroph, while Ptm acts as a hemibiotroph ( Lightfoot and Able, 2010 ). A recent study has demonstrated that Ptm has significantly higher necrotrophic and saprotrophic growth rates than Ptt ( Ronen et al, 2019 ). Several toxins are produced by both forms of P. teres ( Bach et al, 1979 ; Nukina et al, 1980 ; Barrault et al, 1982 ; Friis et al, 1991 ; Weiergang et al, 2002 ), namely proteinaceous toxins and low molecular weight aspergillomarasmine-derived toxins contributing to the necrosis and chlorosis ( Sarpeleh et al, 2007 , 2008 ).…”

Identification and characterization of Pyrenophora species causing leaf spot on oat (Avena sativa) in western China

“…Drechslera leaf spot (DLS) caused by Pyrenophora species (asexual morph: Drechslera ) is common in major cereal‐growing areas of the world (Moolhuijzen et al, 2020). Pyrenophora teres and Pyrenophora graminea cause net blotch and leaf stripe of barley (Arabi et al, 2020; Ronen et al, 2019); Pyrenophora tritici ‐ repentis results in wheat disease tan spot (Liu et al, 2020; Loughman & Deverall, 1986; See et al, 2018); and P . dictyoides and P .…”

“…Drechslera leaf spot (DLS) caused by Pyrenophora species (asexual morph: Drechslera) is common in major cereal-growing areas of the world (Moolhuijzen et al, 2020). Pyrenophora teres and Pyrenophora graminea cause net blotch and leaf stripe of barley (Arabi et al, 2020;Ronen et al, 2019); Pyrenophora tritici-repentis results in wheat disease tan spot (Liu et al, 2020;Loughman & Deverall, 1986;See et al, 2018); and P. dictyoides and P. nobleaewere both cause ryegrass leaf spots (Xue et al, 2020). DLS mainly causes the destruction of the leaf tissues of infected plants, interfering with the accumulation of photosynthates and resulting in low output and quality; this leads to the formation of shrivelled and darkened grains of inadequate quality for milling processing (Bocchese et al, 2006).…”

Genetic Diversity of Barley Foliar Fungal Pathogens

“…Different researchers have examined the genetic variation of P. teres populations together or according to forms separately. Genetic variation in net blotch fungus has been studied in North America [60], Italy [61], Sweden [62], the Northern Hemisphere and Austria [63], Lithuania [64], Australia and South Africa [65][66][67], western Canada [2,58], Turkey [68] and Israel [69] by using different molecular markers.…”

“…It is thought that P. teres isolates obtained from different hosts also have an effect on the genetic diversity of the pathogen population. In Israel, Ronen et al [69] genetically and phenotypically characterized the barley net blotch (Ptt and Ptm) populations obtained from cultivated barley (H. vulgare) and wild barleys (H. vulgare ssp. spontaneum and H. murinum ssp.…”