title: Inverse gene-for-gene interactions contribute additively to tan spot susceptibility in wheat.
abstract: Tan spot susceptibility is conferred by multiple interactions of necrotrophic effector and host sensitivity genes. Tan spot of wheat, caused by Pyrenophora tritici-repentis, is an important disease in almost all wheat-growing areas of the world. The disease system is known to involve at least three fungal-produced necrotrophic effectors (NEs) that interact with the corresponding host sensitivity (S) genes in an inverse gene-for-gene manner to induce disease. However, it is unknown if the effects of these NE-S gene interactions contribute additively to the development of tan spot. In this work, we conducted disease evaluations using different races and quantitative trait loci (QTL) analysis in a wheat recombinant inbred line (RIL) population derived from a cross between two susceptible genotypes, LMPG-6 and PI 626573. The two parental lines each harbored a single known NE sensitivity gene with LMPG-6 having the Ptr ToxC sensitivity gene Tsc1 and PI 626573 having the Ptr ToxA sensitivity gene Tsn1. Transgressive segregation was observed in the population for all races. QTL mapping revealed that both loci (Tsn1 and Tsc1) were significantly associated with susceptibility to race 1 isolates, which produce both Ptr ToxA and Ptr ToxC, and the two genes contributed additively to tan spot susceptibility. For isolates of races 2 and 3, which produce only Ptr ToxA and Ptr ToxC, only Tsn1 and Tsc1 were associated with tan spot susceptibility, respectively. This work clearly demonstrates that tan spot susceptibility in this population is due primarily to two NE-S interactions. Breeders should remove both sensitivity genes from wheat lines to obtain high levels of tan spot resistance.
authors.affiliation: Department of Plant Pathology, North Dakota State University, Fargo, ND, 58108, USA. zhh.liu@ndsu.edu.
authors.forename: Zhaohui
authors.identifier: http://orcid.org/0000-0002-8106-9186
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Plant Pathology, North Dakota State University, Fargo, ND, 58108, USA.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Zurn
authors.affiliation: Department of Plant Pathology, North Dakota State University, Fargo, ND, 58108, USA.
authors.forename: Gayan
authors.initials: G
authors.lastname: Kariyawasam
authors.affiliation: USDA-ARS Cereal Crops Research Unit, Northern Crop Science Laboratory, Fargo, ND, 58102, USA.
authors.forename: Justin D
authors.initials: JD
authors.lastname: Faris
authors.affiliation: Department of Plant Pathology, North Dakota State University, Fargo, ND, 58108, USA.
authors.forename: Gongjun
authors.initials: G
authors.lastname: Shi
authors.affiliation: Department of Plant Pathology, North Dakota State University, Fargo, ND, 58108, USA.
authors.forename: Jana
authors.initials: J
authors.lastname: Hansen
authors.affiliation: Department of Plant Pathology, North Dakota State University, Fargo, ND, 58108, USA.
authors.forename: Jack B
authors.initials: JB
authors.lastname: Rasmussen
authors.affiliation: Department of Plant Pathology, North Dakota State University, Fargo, ND, 58108, USA.
authors.forename: Maricelis
authors.initials: M
authors.lastname: Acevedo
mesh_terms: D001203:Ascomycota; D002874:Chromosome Mapping; D060467:Disease Resistance / Q000235:genetics*; D004843:Epistasis, Genetic; D017343:Genes, Plant; D005838:Genotype; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D040641:Quantitative Trait Loci; D014908:Triticum / Q000235:genetics* / Q000382:microbiology