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Necrotrophic effector‐triggered susceptibility (NETS) underlies the barley–Pyrenophora teres f. teres interaction specific to chromosome 6H

Zhaohui Liu, Danielle J. Holmes, Justin D. Faris, Shiaoman Chao, Robert S. Brueggeman, Michael C. Edwards, Timothy L. Friesen
Molecular plant pathology 2015 v.16 no.2 pp. 188-200
Pyrenophora teres, apoptosis, barley, electrolytes, fungi, gel chromatography, genes, high performance liquid chromatography, inbred lines, leaf blotch, loci, models, oxygen, pathogens, proteinases, quantitative trait loci, reactive oxygen species, species diversity
Barley net form net blotch (NFNB), caused by the necrotrophic fungus Pyrenophora teres f. teres, is a destructive foliar disease in barley‐growing regions worldwide. Little is known about the genetic and molecular basis of this pathosystem. Here, we identified a small secreted proteinaceous necrotrophic effector (NE), designated PttNE1, from intercellular wash fluids of the susceptible barley line Hector after inoculation with P. teres f. teres isolate 0–1. Using a barley recombinant inbred line (RIL) population developed from a cross between the sensitive/susceptible line Hector and the insensitive/resistant line NDB 112 (HN population), sensitivity to PttNE1, which we have named SPN1, mapped to a common resistance/susceptibility region on barley chromosome 6H. PttNE1–SPN1 interaction accounted for 31% of the disease variation when the HN population was inoculated with the 0–1 isolate. Strong accumulation of hydrogen peroxide and increased levels of electrolyte leakage were associated with the susceptible reaction, but not the resistant reaction. In addition, the HN RIL population was evaluated for its reactions to 10 geographically diverse P. teres f. teres isolates. Quantitative trait locus (QTL) mapping led to the identification of at least 10 genomic regions associated with disease, with chromosomes 3H and 6H harbouring major QTLs for resistance/susceptibility. SPN1 was associated with all the 6H QTLs, except one. Collectively, this information indicates that the barley–P. teres f. teres pathosystem follows, at least partially, an NE‐triggered susceptibility (NETS) model that has been described in other necrotrophic fungal disease systems, especially in the Dothideomycete class of fungi.