Molecular screening of wheat entries for resistance to the toxins Ptr ToxA and Ptr ToxB from the tan spot pathogen Pyrenophora tritici-repentis

Intensified wheat production, changes in cultural practices including shifts from conventional tillage to reduced tillage practices, and wheat monoculture involving cultivation of susceptible cultivars has resulted in development of tan spot to epidemic proportions in Kazakhstan. Pyrenophora tritici-repentis, causal agent of tan spot on wheat. In recent years, there has been increasing distribution and harmfulness of P. tritici-repentis on wheat. The aim of the study was to identify and select wheat germplasm resistant to tan spot P. tritici-repentis using molecular markers. The results of field evaluation showed resistant reaction to tan spot in 76 wheat varieties (68%). Molecular screening of wheat germplasm was carried out based on the reaction to the fungal inoculum and to host-specific toxins (HST) produced by the P. tritici-repentis. The wheat germplasm insensitive to the toxins HST Ptr ToxA and Ptr ToxB was selected. As a result of molecular screening of 111 wheat genotypes using SSR marker Xfcp623 linked to insensitivity gene to the selective toxin Ptr ToxA of tan spot, 31 carriers of effective tsn1 gene were identified, which accounted for 27,9% of the genotypes studied. Ten samples of wheat (Jubileynaya 60, TOO11/TOOOO7, F3.71/TRM/VORONA/3/OC14, NANJTNG 82149 KAUZ, ECHA/LI115, Akmola 2, Kazakh-stanskaya rannespelaya, Kazakhstanskaya 25, 428g/MK-122A and 190-Naz/GF55) are characterized with complex resistance to the races Ptr 1 and 5, as well as to 2 toxins (ToxA and ToxB) and to the Septoria nodorum blotch isolate SNB7k. 20 promising wheat lines resistant to tan spot were selected. These genotypes also showed a moderate and high level of field resistance and recommended to use in the breeding programs for resistance to tan spot.

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Pyrenophora tritici-repentis population structure in the Republic of Kazakhstan and identification of wheat germplasm resistant to tan spot

Vavilov Journal of Genetics and Breeding ◽

10.18699/vj20.666 ◽

2020 ◽

Vol 24 (7) ◽

pp. 722-729

Author(s):

A. M. Kokhmetova ◽

N. M. Kovalenko ◽

M. T. Kumarbaeva

Keyword(s):

Wheat Breeding ◽

Tan Spot ◽

Point Of View ◽

Molecular Screening ◽

Breeding Programs ◽

Pyrenophora Tritici Repentis ◽

Ptr Toxa ◽

Race 1 ◽

The Republic ◽

Southeastern Region

Pyrenophora tritici-repentis is a causative agent of tan spot in wheat. In recent years, there has been an increasing spread and harmfulness of wheat tan spot. The aim of the research was to study the racial composition of the P. tritici-repentis population in the Republic of Kazakhstan. A collection of 30 common wheat accessions, including promising lines and cultivars from Kazakhstan and CIMMYT–ICARDA, was assessed for resistance to P. triticirepentis in a greenhouse and characterized using the Xfcp623 molecular marker, diagnostic for the Tsn1 gene. Monosporic isolates of P. tritici-repentis isolated from the southeastern region were assigned to certain races based on the manifestation of symptoms of necrosis/chlorosis on standard differentials (Glenlea, 6B662, 6B365). Five races of P. tritici-repentis have been identified, including races 1, 2, 3, 7 and 8. It has been shown that races 1 and 8 of P. tritici-repentis are dominant. As a result of the analysis of the frequency of occurrence of the P. tritici-repentis races, it was found that race 1 (50 %) producing Ptr ToxA and Ptr ToxB and race 8 (35 %) producing Ptr ToxA, Ptr ToxB and Ptr ToxC turned out to be dominant. From a practical point of view, of greatest interest are 16 wheat samples, which demonstrated resistance to race 1 and confirmed insensitivity to Ptr ToxA in a molecular screening. These include eight Kazakhstani (4_PSI, 10204_2_KSI, 10204_3_KSI, 10205_2_KSI, 10205_3_KSI, 605_SP2, 632_SP2, Dana) and seven foreign lines (KR11-20, KR11-03, KR11-9014, 11KR-13, KR12-9025, KR12-07, GN-68/2003). The results of this study are of interest in wheat breeding programs for tan spot resistance.

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A Novel Source of Resistance in Wheat to Pyrenophora tritici-repentis Race 1

Plant Disease ◽

10.1094/pdis-92-1-0091 ◽

2008 ◽

Vol 92 (1) ◽

pp. 91-95 ◽

Cited By ~ 22

Author(s):

Sukhwinder Singh ◽

William W. Bockus ◽

Indu Sharma ◽

Robert L. Bowden

Keyword(s):

Great Plains ◽

Recombinant Inbred Lines ◽

The United States ◽

Interval Mapping ◽

Tan Spot ◽

Sources Of Resistance ◽

Pyrenophora Tritici Repentis ◽

Ptr Toxa ◽

Chromosome 5B ◽

Race 1

Tan spot, caused by the fungus Pyrenophora tritici-repentis, causes serious yield losses in wheat (Triticum aestivum) and many other grasses. Race 1 of the fungus, which produces the necrosis toxin Ptr ToxA and the chlorosis toxin Ptr ToxC, is the most prevalent race in the Great Plains of the United States. Wheat genotypes with useful levels of resistance to race 1 have been deployed, but this resistance reduces damage by only 50 to 75%. Therefore, new sources of resistance to P. tritici-repentis are needed. Recombinant inbred lines developed from a cross between the Indian spring wheat cvs. WH542 (resistant) and HD29 (moderately susceptible) were evaluated for reaction to race 1 of the fungus. Composite interval mapping revealed quantitative trait loci (QTL) on the short arm of chromosome 3A explaining 23% of the phenotypic variation, and the long arm of chromosome 5B explaining 27% of the variation. Both resistance alleles were contributed by the WH542 parent. The QTL on 5BL is probably tsn1, which was described previously. The 3AS QTL (QTs.ksu-3AS) on 3AS is a novel QTL for resistance to P. tritici-repentis race 1. The QTL region is located in the most distal bin of chromosome 3AS in a 2.2-centimorgan marker interval. Flanking markers Xbarc45 and Xbarc86 are suitable for marker-assisted selection for tan spot resistance.

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Role of Host Sensitivity to Ptr ToxA in Development of Tan Spot of Wheat

Phytopathology ◽

10.1094/phyto.2003.93.4.397 ◽

2003 ◽

Vol 93 (4) ◽

pp. 397-401 ◽

Cited By ~ 51

Author(s):

T. L. Friesen ◽

S. Ali ◽

S. Kianian ◽

L. J. Francl ◽

J. B. Rasmussen

Keyword(s):

Genetic Variance ◽

Dominant Gene ◽

Tan Spot ◽

Wild Type ◽

Pyrenophora Tritici Repentis ◽

Ptr Toxa ◽

Recombinant Inbred Population ◽

Race 2 ◽

Wheat Lines

Pyrenophora tritici-repentis race 2 produces Ptr ToxA, a host-selective toxin previously described as a pathogenicity factor for tan spot on wheat. The objective of this research was to evaluate the role of host sensitivity to toxin, conditioned by a single dominant gene on chromosome 5BL, in the disease development by race 2. An F2-derived F6 recombinant inbred population of 108 wheat lines, produced from crosses of toxin-sensitive, disease-susceptible cv. Kulm with the toxin-insensitive, disease-resistant cv. Erik segregated 1:1 for toxin reaction. However, the population was skewed toward resistance to race 2 of the fungus. Toxin reaction accounted for 24.4% of the genetic variance for disease. Heritability estimates suggested the presence of four to five genes that influence disease reaction in the population. Toxin-insensitive mutants, previously derived Kulm, were susceptible to race 2, although disease developed more slowly on the mutants than it did on the wild-type Kulm. The data indicate that sensitivity to Ptr ToxA influences disease severity in some host genotypes without defining susceptibility.

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Identifcation of genotypescarriers of resistance to tan spot Ptr ToxA and Ptr ToxB of Pyrenophora tritici-repentis in common wheat collection

Vavilov Journal of Genetics and Breeding ◽

10.18699/vj18.440 ◽

2019 ◽

Vol 22 (8) ◽

pp. 978-986 ◽

Cited By ~ 5

Author(s):

A. М. Kokhmetova ◽

Sh. Ali ◽

Z. Sapakhova ◽

M. N. Atishova

Keyword(s):

Molecular Markers ◽

Common Wheat ◽

Wheat Breeding ◽

Tan Spot ◽

Wheat Genotype ◽

Genotype I ◽

Wheat Genotypes ◽

Pyrenophora Tritici Repentis ◽

Ptr Toxa ◽

Race 1

Pyrenophora tritici-repentis(Ptr) is the causative agent of tan spot, one of the yield limiting diseases of wheat, rapidly increasing in wheat growing countries including Kazakhstan. The aim of this study was the identifcation of wheat genotypes with resistance to Ptr race 1 and race 5 and their hostselective eﬀectors (toxins) Ptr ToxA and Ptr ToxB. A common wheat collection of 41 accessions (38 experimental and 3 controls) was characterized using the molecular markersXfcp623andXBE444541, diagnostic for theTsn1andTsc2genes conferring sensitivity to fungal toxins. The coincidence of the markerXBE444541with resistance to race 5 was 92.11 %, and with Ptr ToxB, 97.37 %. Genotyping results using the markerXfcp623confrmed the expected response to Ptr ToxA; the presence/absence of the markerXfcp623completely (100 %) coincided with sensitivity/resistance to race 1 and Ptr ToxA. This demonstrates the reliability of the diagnostic markerXfcp623for identifying wheat genotypes with resistance to the fungus and insensitivity to Ptr ToxA. The study of the reaction of wheat germplasm to the fungal inoculation and toxin infltration showed that out of 38 genotypes analyzed 30 (78 %) exhibited resistance to both race 1 and race 5, and insensitivity to toxins Ptr ToxA and ToxB. Of most signifcant interest are eight wheat genotypes that showed resistance/insensitivity both to the two races and two toxins. The results of phenotyping were reconfrmed by the molecular markers used in this study. Sensitivity to Ptr ToxB is not always correlated with susceptibility to race 5 and is dependent on the host’s genetic background of the wheat genotype, i. e. on a specifc wheat genotype. The results of the study are of interest for increasing the efciency of breeding based on the elimination of the genotypes with the dominant allelesTsn1andTsc2sensitive to the toxins Ptr ToxA and ToxB. The genotypes identifed will be used in wheat breeding for resistance to tan spot.

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The Identification of Two New Races of Pyrenophora tritici-repentis from the Host Center of Diversity Confirms a One-to-One Relationship in Tan Spot of Wheat

Phytopathology ◽

10.1094/phyto.2003.93.4.391 ◽

2003 ◽

Vol 93 (4) ◽

pp. 391-396 ◽

Cited By ~ 131

Author(s):

L. Lamari ◽

S. E. Strelkov ◽

A. Yahyaoui ◽

J. Orabi ◽

R. B. Smith

Keyword(s):

Mirror Image ◽

Tan Spot ◽

Pyrenophora Tritici Repentis ◽

Ptr Toxa ◽

Fertile Crescent ◽

Virulence Pattern ◽

One To One ◽

New Race ◽

New Races ◽

First Time

Pyrenophora tritici-repentis, causal agent of tan spot, induces necrosis and chlorosis in its wheat host. The tan spot system conforms to the toxin model and three host-specific toxins have been identified (Ptr ToxA, Ptr ToxB, and putative Ptr ToxC). Processing of a collection of isolates, obtained in the Fertile Crescent and Caucasus regions, yielded two new virulence patterns. Isolate Az35-5 combined the virulences of races 2 and 5 and was classified in the new race 7. Isolates TS93-71B and TS93-71F had a virulence pattern that combined those of races 2, 3, and 5 and were grouped in the new race 8. Southern analysis revealed that all three isolates possessed copies of the ToxA and ToxB genes, the first time the genes were found in a common background. The production of Ptr ToxA and Ptr ToxB by the isolates was confirmed by western blotting. Virulence patterns suggested that TS93-71B and TS93-71F may also produce Ptr ToxC, even though it was not present at detectable levels in culture filtrates. The identification of races 7 and 8 complete the theoretical maximum number of races that can be differentiated by three loci in the host (23 = 8), assuming a one-to-one relationship. It appears that the wheat/P. tritici-repentis system is a mirror image of the classical gene-for-gene relationship.

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Reaction of Ptr ToxA-Insensitive Wheat Mutants to Pyrenophora tritici-repentis Race 1

Phytopathology ◽

10.1094/phyto.2002.92.1.38 ◽

2002 ◽

Vol 92 (1) ◽

pp. 38-42 ◽

Cited By ~ 38

Author(s):

T. L. Friesen ◽

J. B. Rasmussen ◽

C. Y. Kwon ◽

L. J. Francl ◽

S. W. Meinhardt

Keyword(s):

Great Plains ◽

Dominant Gene ◽

Tan Spot ◽

Mutant Line ◽

Northern Great Plains ◽

Recessive Mutation ◽

Pyrenophora Tritici Repentis ◽

Ptr Toxa ◽

Race 1 ◽

Toxin Sensitivity

The host-selective toxin Ptr ToxA is produced by races 1 and 2 of Pyrenophora tritici-repentis, causal agent of tan spot of wheat. Ptr ToxA has been causally associated with pathogenicity by the race 2 phenotype in this system. However, the role of toxin in disease caused by race 1, the most prevalent form of the fungus in the central and northern Great Plains of North America, has not been rigorously investigated. Three independent wheat lines harboring mutations for insensitivity to Ptr ToxA were derived from ethylmethane sulfonate treatment of the hard red spring wheat cv. Kulm, possessing the single dominant gene for toxin sensitivity. Each of the three mutants was insensitive to Ptr ToxA in bioassays based on necrosis development and electrolyte leakage. Each mutant was crossed to each of the other mutants and to the wild-type Kulm. Segregation data indicate that each mutant line harbors a single recessive mutation for toxin insensitivity that maps to or near the same locus, possibly the toxin-sensitivity gene. Each toxin-insensitive mutant line was susceptible to two isolates of race 1 of P. tritici-repentis. F2 and F3 generations derived from crosses between Kulm and each mutant segregated for toxin reaction. However, segregation for fungal reaction was not evident, and all F3 families were tan spot susceptible regardless of toxin reaction. Host insensitivity to Ptr ToxA is not necessarily equivalent to resistance to race 1. Ptr ToxA should not be used alone as a proxy for fungal inoculations by breeding programs aimed at developing tan spot-resistant wheat.

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PacBio genome sequencing reveals new insights into the genomic organisation of the multi-copy ToxB gene of the wheat fungal pathogen Pyrenophora tritici-repentis

BMC Genomics ◽

10.1186/s12864-020-07029-4 ◽

2020 ◽

Vol 21 (1) ◽

Author(s):

Paula Moolhuijzen ◽

Pao Theen See ◽

Caroline S. Moffat

Keyword(s):

Virulence Factors ◽

Single Gene ◽

Tan Spot ◽

Effector Proteins ◽

Segmental Duplications ◽

Flanking Sequence ◽

Chromosome 10 ◽

Single Chromosome ◽

Pyrenophora Tritici Repentis ◽

Ptr Toxa

Abstract Background Necrotrophic effector proteins secreted by fungal pathogens are important virulence factors that mediate the development of disease in wheat. Pyrenophora tritici-repentis (Ptr), the causal agent of wheat tan spot, has a race structure dependent on the combination of effectors. In Ptr, ToxA and ToxB are known proteinaceous effectors responsible for necrosis and chlorosis respectively. While Ptr ToxA is encoded by the single gene ToxA, ToxB has multiple loci in the Ptr genome, which is postulated to be directly related to the level of ToxB production and leaf chlorosis. Although previous analysis has indicated that the majority of the ToxB loci lie on a single chromosome, the exact number and chromosomal locations for all the ToxB loci have not been fully identified. Results In this study, we have sequenced the genome of a race 5 ToxB-producing isolate (DW5), using PacBio long read technology, and found that ToxB duplications are nested in the complex subtelomeric chromosomal regions. A total of ten identical ToxB gene copies were identified and based on flanking sequence identity, nine loci appeared associated with chromosome 10 and a single copy with chromosome 5. Chromosome 10 multiple ToxB gene loci were separated by large sequence regions between 31 and 66 kb within larger segmental duplications in an alternating pattern related to loci strand, and flanked by transposable elements. Conclusion This work provides for the first time the full accompaniment of ToxB loci and surrounding regions, and identifies the organization and distribution of ten ToxB loci to subtelomeric regions. To our knowledge, this is the first report of an interwoven strand-related duplication pattern event. This study further highlights the importance of resolving the highly complex distal chromosomal regions, that remain difficult to assemble, and can harbour important effectors and virulence factors.

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Inheritance and interaction of spring wheat (Triticum aestivum L.) resistance to Race 2 and Race 3 of Pyrenophora tritici-repentis (Died.) Drechs.

Canadian Journal of Plant Science ◽

10.4141/p00-046 ◽

2001 ◽

Vol 81 (3) ◽

pp. 527-533 ◽

Cited By ~ 10

Author(s):

S. D. Duguid ◽

A. L. Brûlé-Babel

Keyword(s):

Triticum Aestivum ◽

Fungal Pathogen ◽

Nuclear Gene ◽

Triticum Aestivum L ◽

Tan Spot ◽

Pyrenophora Tritici Repentis ◽

Ptr Toxa ◽

Recessive Genes ◽

Race 2 ◽

Dominant Genes

Tan spot is a residue-borne leaf spotting disease caused by the fungal pathogen Pyrenophora tritici-repentis. An understanding of the inheritance of resistance is required to build a strategy for incorporating tan spot resistance into commercial cultivars of wheat. The objectives of this study were to determine the inheritance of host resistance to isolates of races 2 (a necrosis-inducing race) and 3 (a chlorosis-inducing race) of P. tritici-repentis. Crosses were made between seven wheat (Triticum aestivum) genotypes (Katepwa, BH1146, ST15, ST6, Erik, 6B1043, 6B367). Parents, F1, F2and F2-derived F3 populations were inoculated with isolates 86-124 and D308 (races 2 and 3, respectively) of P. tritici-repentis and infiltrated with Ptr ToxA. Resistance to 86-124 and insensitivity to Ptr ToxA was controlled by a single recessive nuclear gene in all of the resistant/susceptible crosses. In contrast, resistance to D308 was controlled by a single dominant nuclear gene in five crosses and two genes in two crosses. In the BH1146/ST15 cross two dominant genes controlled resistance to D308, while in the Katepwa/ST15 cross two recessive genes controlled resistance. Reactions to race 2 were independent of reactions to race 3 and controlled by independent genetic systems. Key words: Triticum aestivum L., Pyrenophora tritici-repentis (Died.) Drechs., disease resistance, inheritance, Ptr necrosis toxin, tan spot

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