Characterizing Virulence of the Pyrenophora tritici-repentis Isolates Lacking Both ToxA and ToxB Genes.

Jingwei Guo,Zhaohui Liu,Gongjun Shi

doi:10.3390/pathogens7030074

Jingwei Guo, Zhaohui Liu + Show 1 more

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https://doi.org/10.3390/pathogens7030074

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Journal: Pathogens	Publication Date: Sep 12, 2018
Citations: 12	License type: CC BY 4.0

Affiliation: North Dakota State University

Abstract

The fungus Pyrenophora tritici-repentis (Ptr) causes tan spot of wheat crops, which is an important disease worldwide. Based on the production of the three known necrotrophic effectors (NEs), the fungal isolates are classified into eight races with race 4 producing no known NEs. From a laboratory cross between 86–124 (race 2 carrying the ToxA gene for the production of Ptr ToxA) and DW5 (race 5 carrying the ToxB gene for the production of Ptr ToxB), we have obtained some Ptr isolates lacking both the ToxA and ToxB genes, which, by definition, should be classified as race 4. In this work, we characterized virulence of two of these isolates called B16 and B17 by inoculating them onto various common wheat (Triticum aestivum L.) and durum (T. turgidum L.) genotypes. It was found that the two isolates still caused disease on some genotypes of both common and durum wheat. Disease evaluations were also conducted in recombinant inbred line populations derived from two hard red winter wheat cultivars: Harry and Wesley. QTL mapping in this population revealed that three genomic regions were significantly associated with disease, which are different from the three known NE sensitivity loci. This result further indicates the existence of other NE-host sensitivity gene interactions in the wheat tan spot disease system.

Highlights

Tan spot is a devastating foliar disease on both common wheat (Triticum aestivum L.) and durum wheat (T. turgidum L.) [1]
QTL mapping in this population revealed that three genomic regions were significantly associated with disease, which are different from the three known necrotrophic effectors (NEs) sensitivity loci
This disease is caused by the fungal pathogen Pyrenophora tritici-repentis (Ptr), which belongs to the family of dothideomycetes in ascomycete

Summary

Introduction

Tan spot is a devastating foliar disease on both common wheat (Triticum aestivum L.) and durum wheat (T. turgidum L.) [1] This disease is caused by the fungal pathogen Pyrenophora tritici-repentis (Ptr), which belongs to the family of dothideomycetes in ascomycete. The lesions can coalesce, which forms a large area of dead leaf tissue These symptoms can be indicative of the necrotrophic nature of lifestyle where the fungus may produce necrotrophic effectors to cause the death of plant cells. Since the 1980s, several studies have revealed that the symptoms of necrosis and chlorosis induced in the host by Ptr were genetically distinct [3,4,5] These studies led to the development of a wheat differential set for tan spot, a lesion type disease rating scale, and a basic race classification system, which have been widely adopted today.

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