Pyrenophora Tritici-repentis Race Research Articles

Changes in Phenolic Acid Levels in Wheat Cultivars Inoculated with Pyrenophora tritici-repentis race 1

Changes in Phenolic Acid Levels in Wheat Cultivars Inoculated with Pyrenophora tritici-repentis race 1

Characterization of Pyrenophora tritici-repentis (tan spot of wheat) races in Kazakhstan

Tan spot, caused by Pyrenophora tritici-repentis, is an economically important foliar disease of wheat in Kazakhstan. Population structure of the pathogen changes every year due to climate change. This study aimed to characterize the race structure of P. tritici-repentis isolates recovered from wheat in south and north Kazakhstan, and identify tan spot resistance in host genotypes based on disease phenotypes and molecular screening. Virulence profiles were determined within 40 isolates of the pathogen from wheat crops during the 2020 growing season. Seven races, (1, 3, 4, 5, 6, 7 and 8) were identified. A collection of 80 wheat accessions, including promising lines and cultivars from Kazakhstan and Russia, were evaluated for their reactions to races 1 and 5 of the pathogen, and to Ptr ToxA and Ptr ToxB, using greenhouse assessments and molecular markers diagnostic for the Tsn1 and Tsc2 genes. From a practical viewpoint, 18 wheat genotypes were insensitive to the two races and the two Ptr toxins. This resistant germplasm can be used in breeding programmes aiming to develop wheat varieties resistant to P. tritici-repentis.

Association Mapping of Seedling Resistance to Tan Spot (Pyrenophora tritici-repentis Race 1) in CIMMYT and South Asian Wheat Germplasm

Tan spot caused by Pyrenophora tritici-repentis (Ptr) is an important disease of wheat in many wheat producing areas of the world. A genome wide association study (GWAS) was conducted using 11,401 SNP markers of the Illumina Infinium 15K Bead Chip with whole genome coverage to identify genomic regions associated with resistance to tan spot in a diverse panel of 184 wheat genotypes originating from South Asia and CIMMYT. The GWAS panel was phenotyped for seedling resistance to tan spot with Ptr race 1 in two greenhouse experiments. Besides CIMMYT germplasm, several lines from South Asia (India, Bangladesh and Nepal) showed good degree of resistance to tan spot. Association mapping was conducted separately for individual experiments and for pooled data using mixed linear model (MLM) and Fixed and random model Circulating Probability Unification (FarmCPU) model; no significant MTAs were recorded through the MLM model, whereas FarmCPU model reported nine significant MTAs located on chromosomes 1B, 2A, 2B, 3B, 4A, 5A, 5B, 6A, and 7D. The long arms of chromosomes 5A and 5B were consistent across both environments, in which the Vrn-A1 locus was found in identified region of chromosome 5A, and MTA at IACX9261 on 5BL appears to represent the resistance gene tsn 1. MTAs observed on chromosomes 1B, 2A, 2B, 3B, 4A, 6A, and 7D have not been reported previously and are likely novel.

Assessing the genetic diversity and characterizing genomic regions conferring Tan Spot resistance in cultivated rye.

Rye (Secale cereale L.) is known for its wide adaptation due to its ability to tolerate harsh environments in semiarid areas. To assess the diversity in rye we genotyped a panel of 178 geographically diverse accessions of four Secale sp. from U.S. National Small Grains Collection using 4,037 high-quality SNPs (single nucleotide polymorphisms) developed by genotyping-by-sequencing (GBS). PCA and STRUCTURE analysis revealed three major clusters that separate S. cereale L. from S. strictum and S. sylvestre, however, genetic clusters did not correlate with geographic origins and growth habit (spring/winter). The panel was evaluated for response to Pyrenophora tritici-repentis race 5 (PTR race 5) and nearly 59% accessions showed resistance or moderate resistance. Genome-wide association study (GWAS) was performed on S. cereale subsp. cereale using the 4,037 high-quality SNPs. Two QTLs (QTs.sdsu-5R and QTs.sdsu-2R) on chromosomes 5R and 2R were identified conferring resistance to PTR race 5 (p < 0.001) that explained 13.1% and 11.6% of the phenotypic variation, respectively. Comparative analysis showed a high degree of synteny between rye and wheat with known rearrangements as expected. QTs.sdsu-2R was mapped in the genomic region corresponding to wheat chromosome group 2 and QTs.sdsu-5R was mapped to a small terminal region on chromosome 4BL. Based on the genetic diversity, a set of 32 accessions was identified to represents more than 99% of the allelic diversity with polymorphic information content (PIC) of 0.25. This set can be utilized for genetic characterization of useful traits and genetic improvement of rye, triticale, and wheat.

Phenotypical and genotypical characterization of Pyrenophora tritici-repentis races in Brazil

Tan spot, caused by Pyrenophora tritici-repentis, is one of the major wheat diseases in southern Brazil as well as in the wheat production areas of several other countries. The fungal isolates have been classified into eight races according to the production of three fungal necrotrophic effectors. The knowledge about the pathogen population structure is essential for disease control strategies, but such information is lacking in Brazil. The aim of this study was to determine the P. tritici-repentis race structure of Brazilian isolates using, for the first time, biological and molecular techniques. P. tritici-repentis isolates were characterized for their virulence on a set of wheat genotypes, and for the presence of ToxA and ToxB gene. The results from the PCR amplification with the gene specific primers showed that all Brazilian P. tritici-repentis isolates carried ToxA, but no ToxB is present. Race typing on the set of wheat genotypes indicate 65% of the isolates were race 2 while 35% were race 1. This is the first study on the P. tritici-repentis race structure in Brazil and the information will be useful to the local wheat breeders who aim to improve tan spot resistance in wheat cultivars.

Reaction of Global Collection of Rye (Secale cereale L.) to Tan Spot and Pyrenophora tritici-repentis Races in South Dakota.

Rye (Secale cereale L.) serves as an alternative host of Pyrenophora tritici-repentis (PTR) the cause of tan spot on wheat. Rye is cultivated as a forage or cover crop and overlaps with a significant portion of wheat acreage in the U.S. northern Great Plains; however, it is not known whether the rye crop influences the evolution of PTR races. We evaluated a global collection of 211 rye accessions against tan spot and assessed the diversity in PTR population on rye in South Dakota. All the rye genotypes were inoculated with PTR races 1 and 5, and infiltrated with Ptr ToxA and Ptr ToxB, at seedling stage. We observed 21% of the genotypes exhibited susceptibility to race 1, whereas, 39% were susceptible to race 5. All 211 accessions were insensitive to both the Ptr toxins. It indicates that though rye exhibits diversity in reaction to tan spot, it lacks Ptr ToxA and ToxB sensitivity genes. This suggests that unknown toxins or other factors can lead to PTR establishment in rye. We characterized the race structure of 103 PTR isolates recovered from rye in South Dakota. Only 22% of the isolates amplified Ptr ToxA gene and were identified as race 1 based on their phenotypic reaction on the differential set. The remaining 80 isolates were noted to be race 4. Our results show that races 1 and 4 are prevalent on rye in South Dakota with a higher frequency of race 4, suggesting a minimal role of rye in the disease epidemiology.

Characterization of Pyrenophora tritici-repentis (Tan Spot of Wheat) Races in Baltic States and Romania.

Tan spot, caused by the fungus Pyrenophora triticirepentis, is economically important foliar disease in Latvia, Lithuania, and Romania; however, race structure from Baltic States and Romania is not known. In this study, we performed genotypic and phenotypic race characterization of a large collection of P. triticirepentis isolates from these countries to determine race structure and utilize this information for better disease management and breeding wheat for tan spot resistance. We characterized 231 single spore isolates from Latvia (n = 15), Lithuania (n = 107), and Romania (n = 109) for Ptr ToxA and Ptr ToxB genes using two genes specific primers. A subset (139) of 231 isolates were further characterized for their race structure by inoculating them individually on tan spot wheat differentials set. Majority (83%) of the 231 isolates amplified Ptr ToxA gene suggesting prevalence of race 1 and 2. Further, phenotypic characterization of 139 isolates also showed wide prevalence of races 1 (68%), 2 (8%), 3 (11%), and 4 (5%) were also identified from Baltic States as well as Romania. Eighteen of the isolates (13%) did not seem to be of any of the eight known races as they lacked Ptr ToxA gene but they behaved like either race 1 or race 2, suggesting possibility of novel toxins in these isolates as their virulence tools.

First Report of Pyrenophora tritici-repentis Race 5 From South Dakota

First Report of <i>Pyrenophora tritici-repentis</i> Race 5 From South Dakota

Association mapping for resistance to tan spot induced by Pyrenophora tritici-repentis race 1 in CIMMYTs historical bread wheat set

Tan spot, a major foliar disease of wheat, is caused by an ascomycete Pyrenophora tritici-repentis (PTR). Association mapping on germplasm collection is a novel approach for the discovery and validation of major genes/QTLs for a trait. Linkage disequilibrium, the genetic basis of association mapping, can be an important tool to identify genomic regions associated with tan spot resistance. Association analysis utilizing the population structure and additive genetic covariance between relatives was conducted for tan spot resistance on a set of historical bread wheat germplasm comprising of 170 lines developed at CIMMYT, Mexico with the genotypic data generated with 1644 molecular markers. Tan spot resistance data was obtained by screening the germplasm with PTR race 1 isolate Ptr-1. Two weeks old seedlings were inoculated and rated 8 days later on a lesion type disease scale. Three experiments were conducted in the greenhouse with each experiment as arranged in completely randomized design with two replicates. Over half of the entries were resistant to tan spot induced by PTR race 1. The genome-wide scan revealed significant marker-phenotype associations on the short arm of chromosomes 1A, 1B, and 6B and long arm of chromosomes 4A, 6A1, 6A2, 2B, 3B, 5B, and 7B that play an important role in conferring resistance to tan spot. Although some genomic regions contributing to tan spot resistance have been previously identified; novel regions on long arm of chromosomes 6A1, 6A2, and 7B, were identified in this study. Findings of this study reveal that a high proportion of CIMMYT wheat germplasm is resistant to tan spot caused by PTR race 1 and genetic base of CIMMYT germplasm resistance involves race specific and non-race specific resistance genes.

Identification of novel genomic regions associated with resistance to Pyrenophora tritici-repentis races 1 and 5 in spring wheat landraces using association analysis

Tan spot, caused by Pyrenophora tritici-repentis, is a major foliar disease of wheat worldwide. Host plant resistance is the best strategy to manage this disease. Traditionally, bi-parental mapping populations have been used to identify and map quantitative trait loci (QTL) affecting tan spot resistance in wheat. The association mapping (AM) could be an alternative approach to identify QTL based on linkage disequilibrium (LD) within a diverse germplasm set. In this study, we assessed resistance to P. tritici-repentis races 1 and 5 in 567 spring wheat landraces from the USDA-ARS National Small Grains Collection (NSGC). Using 832 diversity array technology (DArT) markers, QTL for resistance to P. tritici-repentis races 1 and 5 were identified. A linear model with principal components suggests that at least seven and three DArT markers were significantly associated with resistance to P. tritici-repentis races 1 and 5, respectively. The DArT markers associated with resistance to race 1 were detected on chromosomes 1D, 2A, 2B, 2D, 4A, 5B, and 7D and explained 1.3-3.1% of the phenotypic variance, while markers associated with resistance to race 5 were distributed on 2D, 6A and 7D, and explained 2.2-5.9% of the phenotypic variance. Some of the genomic regions identified in this study correspond to previously identified loci responsible for resistance to P. tritici-repentis, offering validation for our AM approach. Other regions identified were novel and could possess genes useful for resistance breeding. Some DArT markers associated with resistance to race 1 also were localized in the same regions of wheat chromosomes where QTL for resistance to yellow rust, leaf rust and powdery mildew, have been mapped previously. This study demonstrates that AM can be a useful approach to identify and map novel genomic regions involved in resistance to P. tritici-repentis.

Genetics and mapping of resistance to spore inoculum and culture filtrate of Phaeosphaeria nodorum in spring wheat line ND 735

Stagonospora nodorum blotch (SNB), caused by Phaeosphaeria nodorum, is one of the most devastating foliar diseases on wheat ( Triticum aestivum L.) in the northern Great Plains of North America. This study was conducted, under controlled environmental conditions, to elucidate the genetics and map the resistance to SNB caused by spore inoculum and culture filtrate of P. nodorum isolate Sn2000. A hard red spring wheat population was developed from a cross between the susceptible cultivar Steele-ND and the resistant line ND 735 for this study. Two-leaf seedlings of the parents, F 1 and F 2 generations, and F 2:6 recombinant-inbred lines (RILs) were inoculated with spore suspensions while independent two week old seedlings of segregating generations were infiltrated with culture filtrate. Disease reaction was assessed 8 days after inoculation based on a lesion-type scale while plants were evaluated for culture filtrate response four days after infiltration for the presence or absence of necrosis. Genetic analysis revealed that a single recessive gene, Tsn1, in ND 735 confers resistance to both spore suspension and culture filtrate of P. nodorum isolate Sn2000. Mapping analysis using Diversity Arrays Technology (DArT) and simple sequence repeat (SSR) markers indicates the gene, Tsn1, is located on the long arm of chromosome 5B and is flanked by the DArt markers wPt-8285 and wPt-3049 at a distance of 7.0 cM and 2.9 cM, respectively. This gene also controls resistance to tan spot caused by Pyrenophora tritici-repentis race 2. Results of this study reveal that wheat- P. nodorum interaction follows the toxin model of gene-for-gene hypothesis. Additionally, the finding of single gene control in the line ND 735 for both tan spot and SNB enhances the utility of the line ND 735 in wheat breeding program as a source of multiple disease resistance.

Genetic and molecular analysis of wheat tan spot resistance effective against Pyrenophora tritici-repentis races 2 and 5

Tan spot, a major foliar disease of wheat (Triticum aestivum L.), is caused by an ascomycete Pyrenophora tritici-repentis. Both culture filtrates and conidiospore inocula induce disease symptoms in susceptible wheat genotypes. The objectives of this study were to determine and map the genetic control of resistance to spore inocula and culture filtrates of P. tritici-repentis races 2 and 5. The F1 and F2 generations and an F2:6 recombinant inbred lines (RIL) population were developed from a cross between the resistant ND 735 and the susceptible Steele-ND. Disease assessments of the segregating generations were done at the seedling stage using culture filtrates and spore inocula under controlled environmental conditions. Genetic and mapping analyses of the F1 and F2 generations and the RIL by both methods indicated that the same single recessive gene, Tsr1, located on chromosome 5BL, controlled resistance and insensitivity to necrosis induced by race 2. A second recessive gene, designated Tsr6, located on chromosome 2BS, conferred resistance/insensitivity to chlorosis induced by spore inocula or culture filtrates of race 5. Diversity Arrays Technology markers wPt-3049 (2.9 cM) and wPt-0289 (4.6 cM) were closely linked to Tsr1 and Tsr6, respectively. The results further indicated that culture filtrates can be used as surrogates for spore inoculation. Tsr1 and Tsr6 can be selected by marker-assisted selection in breeding for resistance to tan spot.

A quantitative trait locus on chromosome 5B controls resistance of Triticum turgidum (L.) var. diccocoides to Stagonospora nodorum blotch

Stagonospora nodorum blotch (SNB) is an important foliar disease of durum wheat (Triticum turgidum var. durum) worldwide. The combined effects of SNB and tan spot, considered as components of the leaf spotting disease complex, result in significant damage to wheat production in the northern Great Plains of North America. The main objective of this study was the genetic analysis of resistance to SNB caused by Phaeosphaeria nodorum in tetraploid wheat, and its association with tan spot caused by Pyrenophora tritici-repentis race 2. The 133 recombinant inbred chromosome lines (RICL) developed from the cross LDN/LDN(Dic-5B) were evaluated for SNB reaction at the seedling stage under greenhouse conditions. Molecular markers were used to map a quantitative trait locus (QTL) on chromosome 5B, explaining 37.6% of the phenotypic variation in SNB reaction. The location of the QTL was 8.8 cM distal to the tsn1 locus coding for resistance to P. tritici-repentis race 2. The presence of genes for resistance to both SNB and tan spot in close proximity in tetraploid wheat and the identification of molecular markers linked to these genes or QTLs will be useful for incorporating resistance to these diseases in wheat breeding programs.

Molecular mapping of resistance genes to tan spot [Pyrenophora tritici-repentis race 1] in synthetic wheat lines

Synthetic wheat lines (2n = 6x = 42, AABBDD), which are amphiploids developed from the hybrid between tetraploid wheat (Triticum turgidum L., 2n = 4x = 28, AABB) and Aegilops tauschii Coss. (2n = 2x = 14, DD), are important sources of resistance against tan spot of wheat caused by Pyrenophora tritici-repentis. In the present study, inheritance, allelism and genetic linkage analysis in synthetic wheat lines have been carried out. Segregation analysis of the phenotypic and molecular data in F(2:3) populations of CS/XX41, CS/XX45, and CS/XX110 has revealed a 1:2:1 segregation ratio indicating that resistance of tan spot in these synthetic lines is controlled by a single gene. Allelism tests detected no segregation for susceptibility among F(1) and F(2) plants derived from intercrosses of the resistance lines XX41, XX45 and XX110 indicating that the genes are either allelic or tightly linked. Linkage analysis using SSR markers showed that all the three genes: tsn3a in XX41, Tsn3b in XX45 and tsn3c in XX110 are clustered in the region around Xgwm2a, located on the short arm of chromosome 3D. The linked markers and genetic relationship of these genes will greatly facilitate their use in wheat breeding and deployment of cultivars resistant to tan spot.

Reaction of 50 Winter Wheat Cultivars Grown in the Czech Republic to Pyrenophora tritici-repentis Races 1, 3, and 6

The reaction of 50 winter wheat cultivars/lines to artificial infection with Pyrenophora tritici-repentis (PTR) races 1, 3, and 6 was studied under greenhouse conditions. The set of tested cultivars/lines included predominantly cultivars registered in the Czech Republic and some new breeding lines. A high level of resistance to P. tritici-repentis was detected in the cultivars Clarus, Rheia, Cubus, SHMK WW 14-92, &amp;Scaron;&amp;aacute;rka, Vlasta and Dromos (SWS 799.14953), susceptible reactions were observed in the cultivars Caphorn, Corsaire, Karolinum, Heroldo (PBIS 00/91), Hedvika, Biscay, Svitava, Barroko (PBIS 00/140) to all three races tested. The majority of the tested cultivars possess a moderate level of resistance to PTRraces 1, 3, and 6. Significant differences were proved not only in the reaction of the tested cultivars but also in the aggressiveness of the three used isolates. &amp;nbsp;

Annual Meeting, Québec, Quebec, 2006, The Canadian Phytopathological Society / Réunion annuelle, Québec, Québec, 2006, La Société canadienne de phytopathologie

Annual Meeting, Québec, Quebec, 2006, The Canadian Phytopathological Society / Réunion annuelle, Québec, Québec, 2006, La Société canadienne de phytopathologie

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

ABSTRACT 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 F(2)-derived F(6) 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.

Identification of a Chlorosis-Inducing Toxin from Pyrenophora tritici-repentis and the Chromosomal Location of an Insensitivity Locus in Wheat

ABSTRACT Culture filtrate from Pyrenophora tritici-repentis race 1 isolate 78-62 contained a genotype-specific toxin which elicited extensive chlorosis on sensitive wheat genotypes. This toxin was partially purified using gel filtration, ion exchange, and reversed-phase chromatography. The chlorosis toxin was found to be a polar, nonionic, low-molecular-weight molecule. Wheat genotypes infiltrated with crude culture filtrate and partially purified chlorosis toxin exhibited the same chlorotic symptoms seen with conidial inoculations of isolate 78-62. All tested wheat genotypes that exhibited extensive chlorosis to the toxin also exhibited extensive chlorosis to conidial inoculations, and all wheat genotypes insensitive to the toxin did not exhibit extensive chlorosis to conidial inoculations. The recombinant inbred population derived from the cross W-7984 x Opata 85 segregated for chlorosis induction from infiltration with partially purified chlorosis toxin from isolate 78-62. The locus identified by the marker XGli1, associated with resistance to conidial inoculations from race 1 isolates Pti2 and 78-62 and race 3 isolate D308, also was associated with insensitivity to infiltration of crude culture filtrate and partially purified chlorosis toxin. The marker XGli1, located on the short arm of chromosome 1A, is linked to the insensitivity locus within 5.7 cM. We propose that this chlorosis toxin be designated Ptr ToxC.

Saskatchewan Regional Meeting, 2000, The Canadian Phytopathological Society

Pathogenic variability within a population of Mycosphaerella graminicola, a leaf-spotting pathogen of wheat. M. Razavi and G.R. Hughes. Department of Plant Sciences, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada. Genetic control of insensitivity to necrosis induced by the culture filtrate of Pyrenophora tritici-repentis race 2. P.K. Singh and G.R. Hughes. Department of Plant Sciences, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada. Chromosomal Location of Bt10 Common Bunt Resistance. R.E. Knox, J.G. Menzies, Z. Popovic, and J.D. Procunier. Semiarid Prairie Agricultural Research Centre, Agriculture and Agri-Food Canada, Box 1030, Swift Current, SK S9H 3X2, Canada; and (J.G.M., Z.P., J.D.P.) Cereal Research Centre, Agriculture and Agri-Food Canada, 195 Dafoe Road, Winnipeg, MB R3T 2M9, Canada. Effect of lodging resistance and apetalous canola cultivars on sclerotinia stem rot incidence and seed yield. H.R. Kutcher, T.K. Turkington, and G. Clayton. Saskatoon Re-search Centre, Agriculture and Agri-Food Canada, Melfort, SK S0E 1A0, Canada; and (T.T., G.C.) Lacombe Research Centre, Lacombe, AB T4L 1W8, Canada. Dollar spot disease on golf fairway turf in Saskatchewan. J. Drew Smith. Nos. 309–318, 108th Street, Saskatoon, SK S7N 1P8, Canada. Fusarium head blight in common and durum wheat and barley in Saskatchewan in 2000. M.R. Fernandez, P. Pearse, G. Holzgang, and G. Hughes. Semiarid Prairie Agricultural Research Centre, Agriculture and Agri-Food Canada, P.O. Box 1030, Swift Current, SK S9H 3X2, Canada; (P.P., G.H.) Saskatchewan Agriculture and Food, 3085 Albert St., Regina, SK S4S 0B1, Canada; and (G.H.) Department of Plant Science, University of Saskatchewan, Saskatoon, SK S7N 0W0, Canada.