Isolates Of Pyrenophora Tritici-repentis Research Articles

Baseline sensitivity of QoI-resistant isolates of Pyrenophora tritici-repentis from Argentina to fenpicoxamid

Baseline sensitivity of QoI-resistant isolates of Pyrenophora tritici-repentis from Argentina to fenpicoxamid

Characterization of commercial common wheat cultivars for resistance to tan spot causative agent

Tan spot of wheat (pyrenophorosis) is a worldwide spread and economically significant disease of wheat. Growing resistant cultivars is an environmentally friendly method of disease control. The aim of the present work was to assess tan spot resistance in common wheat cultivars recommended for cultivation in the Russian Federation, and to identify the dominant Tsn1 allele using a molecular marker. The assessment involved 39 winter and 31 spring wheat cultivars included in the State Register of Selection Achievement in 2018-2020. Evaluation of wheat resistance was carried out in laboratory conditions under artificial inoculation of seedlings and leaf segments. Two isolates of Pyrenophora tritici-repentis (Died.) Drechs, producing ToxA toxin (I_ToxA) and ToxB toxin (ToxB) were used. The dominant allele of the Tsn1 gene was identified using the Xfcp623 marker. A high level of resistance (R) to both isolates (I_ToxA and I_ToxB) was shown by spring cultivars ‘Grenada’ and ‘Silach’; moderate resistance (MR) was demonstrated by winter cultivars ‘Felicia’ and ‘Akhmat’ and spring cultivars ‘Omskaya 42’, ‘Zauralskaya Zhemchuzhina’, ‘Radmira’, ‘Tarskaya 12’ and ‘Extra’. A resistant reaction (R, MR) to the isolate I_ToxA was typical for 26% of winter cultivars and 45% of spring ones. The number of cultivars resistant to the I_ToxB isolate was significantly higher (59% and 52%, respectively). The total fraction of cultivars resistant to the isolate I_ToxA (reaction R, MR) in the collection of winter wheat was 26% and 45% in the spring wheat collection; while the fractions of cultivars resistant to the I_ToxB isolate in these collections were equal to 59% and 52%, respectively. By using the Xfcp623 marker, the diagnostic product was amplified in winter cultivars ‘Bodry’, ‘Kavalerka’, ‘Timiryazevka 150’, ‘Shef’, ‘Anastasia’, ‘Barynya’, ‘Donskaya Step’, ‘Elanskaya’ and spring cultivars ‘Odeta’, ‘Stolypinskaya 2’, ‘Iren’ 2’ and ‘OMGAU 100’. All these cultivars were moderately susceptible to the isolate I_ToxA, with the exception of ‘Odeta’ and ‘Iren’ 2’, which may indicate a decrease in the expression level of the ToxA gene in genotypes of these cultivars.

Variability of Pyrenophora tritici-repentis isolated from different wheat areas of Tunisia: Morpho-cultural characterization, pathogenic analysis and virulence effector genes

Sixty-three isolates of Pyrenophora tritici-repentis collected from various wheat areas of the north of Tunisia were characterized and studied for their variability. Under in vitro conditions, morpho-cultural characterization showed the presence of several colors of colonies. An inoculation bioassay was performed identifying the presence of three symptoms type i.e., small brown spots, chlorosis, and necrosis with chlorosis. ANOVA of leaf infected area and lesion length data caused by isolates showed significant difference, and Ascending Hierarchical Clustering discriminated them into two distinct pathogenic profiles. Molecular detection of virulence effector genes demonstrated the presence of ToxA, ToxB, and toxb gene individually or in combination, resulting in five different gene profiles. These results indicate large variability of features. Multiple Correspondence Analysis and Ascending Hierarchical Clustering identified four distinct isolates classes. Both pathogenic profiles of isolates appeared in all the groups. Hence, it was not possible to establish a relationship between variability characters and geographical regions from which the isolates were collected.

Races, disease symptoms and genetic variability in Pyrenophora tritici-repentis isolates from Oklahoma that cause tan spot of winter wheat

In recent years, tan spot of wheat caused by the fungus Pyrenophora tritici-repentis has become more prevalent in Oklahoma. Experiments were conducted to investigate the race structure, disease symptoms and genetic variability in P. tritici-repentis isolates collected from winter wheat over three decades. Race determination was conducted for 16 isolates based on expression of necrosis and/or chlorosis produced on wheat differentials. Variability in disease symptoms expressed by 12 isolates was determined on 13 hard red winter wheat cultivars grown in Oklahoma. In addition, genetic variability among 17 isolates was determined using amplified fragment length polymorphism-polymerase chain reaction (AFLP-PCR). All isolates except one (El Reno) were classified as race 1. Isolates varied widely in producing necrosis and/or chlorosis symptoms on wheat cultivars, but necrosis with a chlorotic halo was predominant (56.4%). AFLP-PCR analysis using 13 primer pairs produced a total of 494 alleles of which 285 were polymorphic. The overall genetic diversity among the isolates was 25.2%. Genetic relationships based on cluster analysis and principal component analysis showed only minor differences between isolates, and isolates did not form tight clusters or groups. The isolates of P. tritici-repentis were predominantly race 1; however, they produced a range of tan spot symptoms on wheat cultivars. The lack of distinct genetic grouping by the AFLP marker study indicates that the isolates used in this study likely originated from a single lineage.

Determining the presence of host specific toxin genes, ToxA and ToxB, in New Zealand Pyrenophora tritici-repentis isolates, and susceptibility of wheat cultivars

Tan spot, caused by Pyrenophora tritici-repentis (Ptr), is an important disease of wheat worldwide, and an emerging issue in New Zealand. The pathogen produces host-specific toxins which interact with the wheat host sensitivity loci. Identification of the prevalence of the toxin encoding genes in the local population, and the susceptibility of commonly grown wheat cultivars to Ptr will aid selection of wheat cultivars to reduce disease risk. Twelve single spore isolates collected from wheat-growing areas of the South Island of New Zealand representing the P. tritici-repentis population were characterised for the Ptr ToxA and ToxB genes, ToxA and ToxB, respectively, using two gene specific primers. The susceptibility of 10 wheat cultivars to P. tritici-repentis was determined in a glasshouse experiment by inoculating young plants with a mixed-isolate spore inoculum. All 12 New Zealand P. tritici-repentis isolates were positive for the ToxA gene but none were positive for the ToxB gene. Tan spot lesions developed on all inoculated 10 wheat cultivars, with cultivars ‘Empress’ and ‘Duchess’ being the least susceptible and ‘Discovery’, ‘Reliance’ and ‘Saracen’ the most susceptible cultivars to infection by the mixed-isolate spore inoculum used. The results indicated that the cultivars ‘Empress’ and ‘Duchess’ may possess a level of tolerance to P. tritici-repentis and would, therefore, be recommended for cultivation in regions with high tan spot incidence.

Simple sequence repeat marker analysis reveals grouping of Pyrenophora tritici-repentis isolates based on geographic origin

The population structure and genetic diversity of Pyrenophora tritici-repentis from hexaploid wheat were examined using 51 simple sequence repeat (SSR) markers designed to represent each chromosome of the pathogen. A total of 83 isolates representing races 1 and 2 of Ptr were analysed, including 35 isolates from Canada and 48 isolates from Iran. Isolates of the same two races but originating from different regions were compared in order to examine the effect of geographic origin on grouping. Most of the variation (91%) was observed within the examined populations and only 9% between populations. In addition, a moderate amount of gene flow (Nm = 2.8134) was found between populations. The average gene diversity and the percentage of polymorphic loci were estimated to be 0.2764 and 68.63%, respectively. Applying the unweighted pair group method with arithmetic mean procedure and Dice similarity coefficient revealed no obvious clustering of isolates based on race designation. In contrast, the grouping of isolates was consistent with geographic origin to some extent, with most isolates from Iran and Canada clustering separately regardless of race. These results indicate a link between geographic origin and the grouping of Ptr isolates, which could be detected by comparison of the same two races from two different regions. Previous research compared variable races, making it difficult to draw conclusions regarding the effect of geographic origin.

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.

Race structure of Pyrenophora tritici-repentis in Morocco

The virulence of 135 single-spore isolates of Pyrenophora tritici-repentis , collected from durum wheat fields representing most of the major agro-ecological zones of Morocco from 2013 to 2015, was assessed on six international differential wheat genotypes under controlled conditions. Races 1, 5, 6 and 7 were identified with races 5 and 6 being most frequent, representing 47% and 44% of isolates tested, respectively. Only eight isolates (6%) collected at two research stations and a farm field near a station in 2014 and 2015 were race 1, while three isolates collected in 2014 in a farm field in north-eastern Morocco were race 7. The uniform race structure in farm fields may be due to overreliance on a limited and narrow genetic base for durum wheat crops in Morocco. However, the identification of four races is significant since P. tritici-repentis can generate new combinations of virulence, thereby increasing race diversity. Combined with the low wheat diversity this may lead to future severe disease epidemics.

Influence of nitrogen sources on growth and mycotoxin production by isolates of Pyrenophora tritici-repentis from wheat

The fungus Pyrenophora tritici-repentis (Died.) Drechs. infects the leaves and kernels of wheat, causing tan spot and red smudge, respectively. Isolates of P. tritici-repentis have been reported to be both phytopathogenic and mycotoxigenic. This research investigates the influence of nitrogen sources on growth and production of mycotoxins by eight different isolates of P. tritici-repentis. A synthetic agar medium (SAM) was used with different nitrogen sources, both inorganic [(NH4Cl, NH4NO3 and (NH4)2SO4)] and organic (l-alanine, l-histidine, and l-lysine), at a concentration of 37.5mmolL−1. Individual isolates exhibited different growth rates that varied according to the nitrogen source added to the medium. The choice of nitrogen source also had a major effect on production of the mycotoxins emodin, catenarin and islandicin. The highest concentrations of emodin, 54.40±4.46μgg−1, 43.07±23.39μgg−1 and 28.91±4.64μgg−1 of growth medium, were produced on the complex medium (V8-potato dextrose agar) by the isolates Alg-H2, 331-2 and TS93-71B, respectively. A relatively high concentration of emodin also was produced by isolates Az35-5 (28.29±4.71μgg−1 of medium) and TS93-71B (27.03±4.09μgg−1 of medium) on synthetic medium supplemented with l-alanine. The highest concentrations of catenarin (174.54±14.46μgg−1 and 104.87±6.13μgg−1 of medium) were recorded for isolates TS93-71B and Alg-H2 on synthetic medium supplemented with l-alanine and NH4Cl, respectively. The highest concentration of islandicin (4.64±0.36μgg−1 medium) was observed for isolate 331-2 in the presence of l-lysine. There was not a close relationship between mycelial growth and mycotoxin production by the fungal isolates. This is the first report on the influence of nitrogen sources on the production of mycotoxins by P. tritici-repentis.

Evaluation and Association Mapping of Resistance to Tan Spot and Stagonospora Nodorum Blotch in Adapted Winter Wheat Germplasm.

Tan spot and Stagonospora nodorum blotch (SNB), often occurring together, are two economically significant diseases of wheat in the Northern Great Plains of the United States. They are caused by the fungi Pyrenophora tritici-repentis and Parastagonospora nodorum, respectively, both of which produce multiple necrotrophic effectors (NE) to cause disease. In this work, 120 hard red winter wheat (HRWW) cultivars or elite lines, mostly from the United States, were evaluated in the greenhouse for their reactions to the two diseases as well as NE produced by the two pathogens. One P. nodorum isolate (Sn4) and four Pyrenophora tritici-repentis isolates (Pti2, 331-9, DW5, and AR CrossB10) were used separately in the disease evaluations. NE sensitivity evaluation included ToxA, Ptr ToxB, SnTox1, and SnTox3. The numbers of lines that were rated highly resistant to individual isolates ranged from 11 (9%) to 30 (25%) but only six lines (5%) were highly resistant to all isolates, indicating limited sources of resistance to both diseases in the U.S. adapted HRWW germplasm. Sensitivity to ToxA was identified in 83 (69%) of the lines and significantly correlated with disease caused by Sn4 and Pti2, whereas sensitivity to other NE was present at much lower frequency and had no significant association with disease. As expected, association mapping located ToxA and SnTox3 sensitivity to chromosome arm 5BL and 5BS, respectively. A total of 24 potential quantitative trait loci was identified with -log (P value) > 3.0 on 12 chromosomes, some of which are novel. This work provides valuable information and tools for HRWW production and breeding in the Northern Great Plains.

Distribution of races and Tox genes in Pyrenophora tritici-repentis isolates from wheat in Argentina

Fil: Moreno, Maria Virginia. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Agronomia; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Global population structure and migration patterns suggest significant population differentiation among isolates of Pyrenophora tritici-repentis

The global population structure and migration patterns of foliar wheat pathogen Pyrenophora tritici-repentis (PTR) were determined using 12 microsatellite loci. Analysis of 439 single-spore isolates of PTR from five continents (18 wheat-producing countries) showed high level of genetic diversity, and moderate to high population differentiation between continents. A high level of gene diversity (HS=0.31 to 0.56) was observed within each population. Allelic richness indicated the European and the North American population have a high effective population size. Bayesian analyses showed five clusters where the inferred clusters did not represent geographical populations. Corrected standardized fixation index (GST″) estimates ranged from 0.042 to 0.265 between populations, indicating low to high genetic differentiation exists between populations. We found migration (gene flow) between old world (Europe) and new world (Americas) population; however, little migration was observed among other continents. The European population was the major source of immigrants for the North American, South American, Australian and the Asian populations. Significant (P<0.001) linkage disequilibrium (LD) was detected in the Australian and the South American populations. In contrast, non-significant (P<0.001) LD values were observed in the Asian, European and the North American populations. Overall, our findings demonstrate the population differentiation exits among the global populations and strict quarantine measures should be applied to prevent the accelerated global spread of this pathogen.

Genetic analysis and comparative virulence of isolates of Pyrenophora tritici-repentis from wheat in Argentina

Tan spot caused by the fungus Pyrenophora tritici-repentis, occurs in many wheat-growing regions worldwide and is considered among the major diseases of wheat in Argentina. In nature, this pathogen reproduces both sexually and asexually, but the extent of genetic variability in the P. tritici-repentis Argentinian population is unknown. The genetic structure of P. tritici-repentis populations was assessed with amplified polymorphic markers with sequence data from the internal transcribed spacer region of the ribosomal deoxyribonucleic acid (DNA) (ITS) analysis. Eighty-nine (89) P. tritici-repentis isolates were collected from 14 geographically distinct regions of the wheat-growing areas in Argentina. Clustered analysis of random amplified polymorphic DNAs (RAPDs) showed seven different groups of isolates at 43% similarity. Analyses of the ITS1 and ITS4 primers grouped the isolates in fifteen separated clusters and resulted in a sensible method by providing valuable information on the genotypic diversity detected in the populations. Additionally, diversity was assayed by analysis of severity and type of symptoms reaction indicating significant differences between cultivars and isolates. The utility of cleaved amplified polymorphic sequence analysis for molecular differentiation of pathotypes was demonstrated. It appears that the P. tritici-repentis population in Argentina is fairly diverse, and caution should be taken in any breeding strategy, since rare pathotypes may quickly become predominant if susceptible host genotypes are continuously grown. Key words: Tan spot, Pyrenophora tritici-repentis, wheat, genetic diversity, virulence.

Pyraclostrobin sensitivity of baseline and fungicide exposed isolates of Pyrenophora tritici-repentis

Tan spot, caused by Pyrenophora tritici-repentis, is an important disease of wheat (Triticum aestivum L.) in the United States (U.S). Wheat growers sometimes rely on fungicide applications to manage foliar diseases. Pyraclostrobin is one of the recommended quinone outside inhibitor (QoI) fungicides and is commonly used to manage tan spot on wheat. Although P. tritici-repentis isolates has been reported as insensitive to QoI fungicides in Europe, little is known regarding the sensitivity of the P. tritici-repentis population to fungicides in the U.S. Twenty-eight isolates collected prior to 1997 and 136 isolates collected from pyraclostrobin treated fields in North Dakota were collected in 2007 and 2009 to determine if P. tritici-repentis isolates can use alternative respiration in the presence or absence of salicylhydroxamic acid (SHAM) in vitro and to determine the effective fungicide concentration that inhibited conidia germination by 50% (EC50). Six of 10 baseline isolates of P. tritici-repentis assayed had significantly higher (P ≤ 0.05) EC50 values when SHAM was not added to agar medium amended with pyraclostrobin, confirming that the fungus can utilize alternative respiration to overcome QoI toxicity in vitro. EC50 values of the baseline isolates ranged from 0.0012 to 0.0024 μg/ml (mean EC50 value of 0.0017 μg/ml and standard deviation is ±0.00039 μg/ml) while EC50 values of the 136 fungicide exposed isolates ranged from 0.0013 μg/ml to 0.0027 μg/ml (mean EC50 value of 0.0017 μg/ml and standard deviation is ±0.00030). These results indicate that the field exposed isolates have not shifted to reduced sensitivity to pyraclostrobin and that the baseline sensitivity values can be useful for a fungicide resistance monitoring program for P. tritici-repentis in the U.S.

Influence of carbon source on growth and mycotoxin production by isolates of Pyrenophora tritici-repentis from wheat

The fungus Pyrenophora tritici-repentis can infect wheat kernels, causing red smudge, and has been shown to produce the anthraquinone mycotoxins emodin, catenarin, and islandicin. The growth of 8 fungal isolates from diverse regions was evaluated on various culture media and was found to be generally slowest on the semisynthetic Fries medium. The choice of carbon source had a significant effect on mycotoxin production, as assessed by high-performance liquid chromatography. The highest emodin concentration (194.18 ± 16.26 µg/g medium) was observed for isolate Alg 3-24 on Fries medium supplemented with fructose, while the highest catenarin concentration (302.54 ±13.92 µg/g medium) was observed for TS93-71B on Fries medium supplemented with starch. Islandicin was not produced by any isolate under the conditions tested. Evaluation of the dynamics of mycotoxin production by isolate 331-2 on V8-potato dextrose agar medium revealed a rapid accumulation of emodin and catenarin during the first week of incubation, followed by a large decline by 14 days. Differences in the growth of and mycotoxin production by isolates of P. tritici-repentis likely resulted from the differential composition of the media and (or) intraspecies variability. Accordingly, the optimization of growth medium should be considered when evaluating the potential of specific isolates for mycotoxin production.

Influence of water activity and temperature on growth and mycotoxin production by isolates of Pyrenophora tritici-repentis from wheat

Pyrenophora tritici-repentis is a phytopathogenic fungus that can infect wheat kernels and leaves, causing red smudge and tan spot, respectively. A number of P. tritici-repentis isolates have been shown to be mycotoxigenic, producing the anthraquinone mycotoxins emodin, catenarin and islandicin. The influence of water activity ( a w; 0.75–0.99 a w) and temperature (5–45 °C) on growth and mycotoxin production by five isolates of P. tritici-repentis was studied. All isolates grew at 0.95–0.99 a w and 15–25 °C on a wheat-based medium, with three isolates also producing small colonies at 5 °C. The optimal growth conditions for all isolates consisted of 0.99 a w and 25 °C, and growth was significantly reduced at 0.95 a w and/or 15 °C. Emodin and catenarin were detected in cultures of all isolates, at concentrations ranging from 0.06 ± 0.04 to 11.31 ± 2.96 µg emodin/g medium, and from 0.09 ± 0.06 to 53.42 ± 4.36 µg catenarin/g medium. In most isolates, the concentrations of emodin and catenarin declined under suboptimal growth conditions. However, in some isolates, significant increases in the concentrations of both compounds were observed under suboptimal conditions. Islandicin was detected in cultures of only three isolates, at concentrations ranging from 0.07 ± 0.05 to 5.69 ± 0.76 µg/g medium. The results suggest that growth and mycotoxin formation by P. tritici-repentis are markedly influenced by a w and temperature, and that this fungus is hygrophilic. Therefore, infection and contamination of kernels by P. tritici-repentis are likely to occur in the field rather than in storage. To our knowledge, this is the first study on the effect of environmental factors on mycelial growth and mycotoxin production by P. tritici-repentis.

Prevalence of ToxA-sensitive alleles of the wheat gene Tsn1 in Australian and Chinese wheat cultivars

A recent survey of worldwide isolates of Stagonospora nodorum showed that all Australian isolates expressed the host-specific toxin ToxA (Stukenbrock and McDonald 2007). In contrast, very few Chinese isolates did. All the Australian Pyrenophora tritici-repentis isolates that were tested expressed ToxA. We therefore postulated that the wheat gene that confers sensitivity to ToxA, Tsn1, would vary in prevalence in wheat cultivars in use in the two countries. Contrary to expectation, 10 out of 21 Chinese cultivars responded to ToxA as did 26 out of 46 Australian cultivars. The result suggests that ToxA has not had a determining effect on the survival of wheat cultivars in either country. They also suggest that despite the widespread use of Tsn1 markers in Australia, sensitive alleles are still commonplace. The removal of sensitive alleles from breeders’ lines could be readily achieved and could significantly affect the resistance of wheat to both diseases.

Genetic diversity of Pyrenophora tritici-repentis isolates as revealed by AFLP analysis.

The population structure and genotypic diversity of 100 Pyrenophora tritici-repentis isolates originating mainly from the Czech Republic, but also from the Slovak Republic, Russia, Canada, the USA and Argentina, were studied with molecular markers. As an outgroup, eight isolates of Pyrenophora teres f. teres and 7 isolates of P. teres f. maculata were added into the analysis. A total of 115 single monosporic cultures were subjected to molecular marker analysis using the amplified fragment length polymorphism technique (AFLP). When both species of Pyrenophora were analysed with 21 AFLP primer combinations, 664 polymorphic bands were detected. Considering only P. tritici-repentis isolates, 335 polymorphic bands were detected, which corresponds to an average of 16.0 bands per primer combination. UPGMA cluster analysis based on genetic distances clearly distinguished between P. teres and P. tritici-repentis isolates. Isolates of race 4 and isolates collected from non-wheat host plants grouped into two clusters distinct from a main cluster formed by the rest of P tritici-repentis isolates. Analysis of molecular variance (AMOVA) showed that 98.1% of genetic variance occurred within local populations and 1.9% was found among populations. The occurrence of sexual reproduction and longdistance dispersal of inoculum could contribute to the occurrence of genetic variability independently of race structure or geographic origin.

Pathogenic and molecular variability among isolates of Pyrenophora tritici-repentis, causal agent of tan spot of wheat in Argentina

Tan spot, caused by Pyrenophora tritici-repentis, is a common disease of wheat (Triticum aestivum) responsible for economic losses in some wheat growing areas worldwide. In this study the pathogenic and genetic diversity of 51 P. tritici-repentis isolates collected from different ecological regions of Argentina were analyzed. Virulence tests were conducted on 10 selected wheat cultivars: Buck Halcon, Chris, Gabo, Glenlea, Klein Dragon, Klein Sendero, Max, ND 495, ProInta Guazu and ProInta Imperial. Data revealed significant differences between all main factors evaluated and the interactions for 19 of the isolates analyzed. Based on the reaction type of each isolate/cultivar combination, 48 different pathogenic patterns were detected. The molecular analysis using Inter-Simple Sequence Repeats (ISSR) revealed the existence of 36 different haplotypes among 37 isolates of P. tritici-repentis originally selected for this study. These results indicate that P. tritici-repentis on wheat in Argentina is a heterogeneous fungus, implying that screening wheat germoplasm for resistance for tan spot disease requires a wide range of pathogen isolates.

Annual Meeting, Saskatoon, Saskatchewan, 2007 / Réunion annuelle, Saskatoon, Saskatchewan, 2007

Annual Meeting, Saskatoon, Saskatchewan, 2007 / Réunion annuelle, Saskatoon, Saskatchewan, 2007