Puccinia Striiformis Research Articles

Characterization of stem, stripe and leaf rust resistance in Tajik bread wheat accessions

Stem rust [causal organism: Puccinia graminis f. sp. tritici (Pgt)], stripe rust [Puccinia striiformis f. sp. tritici (Pst)], and leaf rust [Puccinia triticina (Pt)] are important fungal diseases of wheat in Central Asia and worldwide. Therefore, identification of seedling and adult plant resistance (APR) genes is of major importance for the national wheat breeding program in many countries. The objectives of this study were to identify genes that confer seedling and APR resistances in widely grown wheat cultivars, landraces and advanced lines from Tajikistan. A total of 41 wheat accessions were inoculated with eleven races of Pgt, twelve races of Pst and nine races of Pt for postulation of Sr (stem rust), Yr (yellow or stripe rust), and Lr Lr (leaf rust) resistance genes at the seedling stage. In addition, all of the accessions were tested in field trials for the response to stem rust and stripe rust. Genes for seedling stem rust resistance (i.e. Sr5, Sr6, Sr11, Sr31, and Sr38), stripe rust resistance (Yr9, Yr17, and Y27), and leaf rust resistance (Lr16 and Lr26) were postulated in the Tajik wheat. The presence of the pleiotropic APR genes Sr2/Yr30/Lr27 (associated with pseudo-black chaff phenotype) and Lr34/Yr18/Sr57 (associated with leaf tip necrosis phenotype), and also Lr37 were assessed in the field and confirmed with linked molecular markers. In most of the wheat accessions, resistance genes could not be postulated because their infection types did not match the avirulence or virulence profile of the Pgt, Pst and Pt races tested. Six, seven, and nine accessions were identified that likely possess new genes for resistance to stem rust, stripe rust, and leaf rust, respectively, which have not been described previously. The research demonstrates the presence of effective seedling resistance and APR genes in widely grown wheat accessions that could facilitate further rust resistance breeding in the national wheat breeding program in Tajikistan.

A major QTL co-localized on chromosome 6BL and its epistatic interaction for enhanced wheat stripe rust resistance.

Co-localization of a major QTL for wheat stripe rust resistance to a 3.9-cM interval on chromosome 6BL across both populations and another QTL on chromosome 2B with epistatic interaction. Cultivars with diverse resistance are the optimal strategy to minimize yield losses caused by wheat stripe rust (Puccinia striiformis f. sp. tritici). Two wheat populations involving resistant wheat lines P10078 and Snb"S" from CIMMYT were evaluated for stripe rust response in multiple environments. Pool analysis by Wheat660K SNP array showed that the overlapping interval on chromosome 6B likely harbored a major QTL between two populations. Then, linkage maps were constructed using KASP markers, and a co-localized locus with large effect on chromosome 6BL was detected using QTL analysis in both populations. The coincident QTL, named QYr.nwafu-6BL.2, explained 59.7% of the phenotypic maximum variation in the Mingxian 169 × P10078 and 52.5% in the Zhengmai 9023 × Snb"S" populations, respectively. This co-localization interval spanning 3.9cM corresponds to ~ 30.5-Mb genomic region of the newest common wheat reference genome (IWGSC RefSeq v.1.0). In addition, another QTL was also detected on chromosome 2B in Zhengmai 9023 × Snb"S" population and it can accelerate expression of QYr.nwafu-6BL.2 to enhance resistance with epistatic interaction. Allowing for Pst response, marker genotypes, pedigree analysis and relative genetic distance, QYr.nwafu-6BL.2 is likely to be a distinct adult plant resistance QTL. Haplotype analysis of QYr.nwafu-6BL.2 revealed specific SNPs or alleles in the target region from a diversity panel of 176 unrelated wheat accessions. This QTL region provides opportunity for further map-based cloning, and haplotypes analysis enables pyramiding favorable alleles into commercial cultivars by marker-assisted selection.

Ethyl-methanesulfonate mutagenesis generated diverse isolates of Puccinia striiformis f. sp. tritici, the wheat stripe rust pathogen.

Puccinia striiformis f. sp. tritici (Pst) is an obligate biotrophic fungal pathogen causing stripe rust, one of the most important diseases of wheat worldwide. Mutation is considered as one of the major mechanisms causing virulence changes in the pathogen population, but experimental evidence is limited. To study the effect of mutation on pathogen variation, we developed 33 mutant isolates by treating urediniospores of Pst race PSTv-18, avirulent to all of the 18 Yr single-gene lines used to differentiate Pst races, with ethyl methanesulfonate (EMS). These isolates were characterized as 24 races, including 19 new races, through virulence testing on the set of 18 wheat Yr single-gene differential lines; and as 21 multi-locus genotypes with 19 simple sequence repeat and 48 single-nucleotide polymorphism markers. Most of the mutant isolates had more than one avirulence gene and more than one marker locus changed compared to the wild type isolate, indicating that EMS is able to cause mutations at multiple genome sites. The results showed that mutation can cause substantial changes in both avirulence and other genomic regions. The different frequencies of virulence among the mutant isolates suggested homozygous or heterozygous avirulence loci in the parental isolate, or relative ease of mutation at some avirulence loci. The results are useful for understanding evolutionary mechanisms of the important fungal pathogen.

Identification and validation of a novel major QTL for all-stage stripe rust resistance on 1BL in the winter wheat line 20828.

A major, likely novel stripe rust resistance QTL for all-stage resistance on chromosome arm 1BL identified in a 1.76-cM interval using a saturated linkage map was validated in four populations with different genetic backgrounds. Stripe rust is a globally important disease of wheat. Identification and utilization of new resistance genes are essential for breeding resistant cultivars. Wheat line 20828 has exhibited high levels of stripe rust resistance for over a decade. However, the genetics of stripe rust resistance in this line has not been studied. A set of 199 recombinant inbred lines (RILs) were developed from a cross between 20828 and a susceptible cultivar Chuannong 16. The RIL population was genotyped with the Wheat55K SNP (single nucleotide polymorphism) array and SSR (simple sequence repeat) markers and evaluated in four environments with current predominant Puccinia striiformis f. sp. tritici t races including CYR32, CYR33 and CYR34. Four stable QTL were located on chromosomes 1B (2 QTL), 4A and 6A. Among them, the major QTL, QYr.sicau-1B.1 (LOD = 23-28, PVE = 16-39%), was localized to a 1.76-cM interval flanked by SSR markers Xwmc216 and Xwmc156 on chromosome 1BL. Eight resistance genes were previously identified in the physical interval of QYr.sicau-1B.1. Compared with previous studies, QYr.sicau-1B.1 is a new gene for resistant to stripe rust. It was further verified by analysis of the closely linked SSR markers Xwmc216 and Xwmc156 in four other populations with different genetic backgrounds. QYr.sicau-1B.1 reduced the stripe rust disease index by up to 82.8%. Three minor stable QTL (located on chromosomes 1B, 4A and 6A, respectively) also added to the resistance level of QYr.sicau-1B.1. Our results provide valuable information for further fine mapping and cloning as well as molecular-assisted breeding with QYr.sicau-1B.1.

Identification of Berberis Species Collected from the Himalayan Region of Pakistan Susceptible to Puccinia striiformis f. sp. tritici.

Puccinia striiformis f. sp. tritici (Pst), the stripe rust pathogen infecting cereal crops and grasses, was believed to have a hemicyclic life cycle consisting of uredinial and telial stages before the recent discovery of barberry (Berberis spp.) as an alternate (aecial) host for the fungus. This discovery has improved the understanding of the biology of the stripe rust pathogen. The Himalayan and near-Himalayan regions of Pakistan, China, and Nepal are considered as the center of diversity for Pst pathogen. High genetic diversity has been reported in these areas, probably resulting from the sexual reproduction of the stripe rust fungus. To determine if Berberis species growing in Pakistan are susceptible to Pst, we collected seeds of five species and two subspecies from the Himalayan region in 2016 and inoculated the seedlings with germinated teliospores of a Pakistani Pst isolate under controlled conditions. Pycnia and aecia were produced on all inoculated plants of these species and subspecies, and were demonstrated as Pst by successful infection of wheat plants with aeciospores. This study showed that the tested Pakistani Berberis species and subspecies are susceptible to Pst under controlled conditions.

Effect of Varieties, Fungicides and Application Frequencies to Wheat Yellow Rust Disease (<i>Puccinia striiformis</i> f. sp. <i>tritici</i>) Management in Arsi Highlands of Ethiopia

Wheat is one of Ethiopia’s foremost important cereal crops in terms of area coverage and volume produced. However, the production and productivity of wheat is constrained by various biotic and a biotic stresses, among which wheat yellow rust disease caused by <i>Puccinia striiformis</i> f.sp. <i>tritici</i> is the one. Field experiments were conducted to develop integrated wheat yellow rust management strategy based on optimal frequency of fungicide application and wheat varieties combination at hotspot environments of Meraro and Bekoji, Arsi zone, in 2017 main cropping season. Treatments included two different fungicides, Epoxiconazole + Thiophanate-methyl and Propiconazole applied in two frequencies; and four bread wheat cultivars (Kubsa, Danda'a, Lemu and Wane), known for their differential reaction to the disease. Unsprayed controls were also included for comparison purposes. The experiment was laid out in randomized complete block design in factorial arrangement with three replications. Terminal severity levels up to 13%, 37%, 53% and 90% at Bekoji, and 11.67%, 53.3%, 58.33%, 92% at Meraro were recorded on the unsprayed varieties of Wane, Lemu, Danda’a and Kubsa, respectively. Twice application frequency of Epoxiconazole + Thiophanate-methyl resulted in a significant (P<0.01) grain yield increment of up to 95.3%, 76.4%, and 1086.8% at Bekoji and 129.7%, 135.5%, 2883.2% at Meraro on unsprayed plots of Lemu, Danda’a, and Kubsa, respectively. But yield increments as a result of fungicide applications were relatively lower (29.8% and 65.9% at Bekoji and Meraro, respectively) on the resistant variety Wane. Twice application of Epoxiconazole + Thiophanate-methyl at 15 days interval starting from the appearance of disease has proved the most effective in terms of reducing the level of stripe rust, and increasing grain and crop biomass yield. The current findings demonstrate the role fungicides and host resistance may play in effectively managing stripe rust of wheat. However, further research is needed to come up with other management options to sustainable and cost effective manage the disease under different agro-ecological settings.

Assessment of yield losses due to stripe rust caused by Puccinia striiformis f. sp. tritici on bread wheat cultivars in Punjab

stripe rust caused by P. striiformis Westend f.sp. tritici eriks. is an important and the most damaging disease of wheat, appearing continuously since 2006–07 in sub-mountainous districts of Punjab, and causes enormous yield losses every year. For the effective and economical management of stripe rust, the present study was aimed to determine the extent of losses caused by stripe rust in different wheat cultivars recommended in Punjab and North Western Plains Zone (NWPZ) with different levels of resistance. The experiment was conducted in Randomized Block design in pair treatment (Protected versus unprotected) using systemic fungicide propiconazole (Tilt 25EC) @ 0.1% (200 ml in 200 litres of water/acre) during two crop seasons i.e. 2016–17 and 2017–18 on seven wheat varieties, namely HD 3086 (Resistant), PBW 725 (Resistant), PBW 677, Unnat PBW 343 (PBW 723), PBW 621, HD 2967 and PBW 343 (Susceptible check)). Three sprays of fungicide were given from disease initiation onwards at 15 days interval on the susceptible varieties. no disease was observed in the test varieties under protected conditions and it varied from 0–80S under unprotected conditions. The effect of stripe rust severity on grain yield was significant (P<0.05) between protected and unprotected plots in case of moderately susceptible and susceptible cultivars. in susceptible variety PbW 343, the yield losses were estimated to be 75.1%. the disease parameters were negatively correlated with the yield. The cost benefit ratio implied that maximum net returns were obtained in fungicide treated plots of susceptible varieties followed by moderately susceptible varieties and were negative for resistant cultivars.

Complete genome sequence of a novel mitovirus from the wheat stripe rust fungus Puccinia striiformis.

The complete genome of a novel mycovirus, Puccinia striiformis mitovirus 1 (PsMV1), derived from the wheat stripe rust fungus Puccinia striiformis strain SCSN-10, was sequenced and analyzed. The full-length cDNA sequence is 2496bp in length with a predicted AU content of 57.65% in the genomic RNA. Sequence analysis indicated that a single large open reading frame (ORF) is present on the positive strand when the fungal mitochondrial genetic code is used. The single ORF encodes a putative RNA-dependent RNA polymerase of 743 amino acids with a molecular mass of 84.9kDa that shares the closest similarity with the corresponding proteins of Cronartium ribicola mitovirus 5 and Helicobasidium mompa mitovirus 1-18 (34% and 35% aa sequence identity, respectively). Phylogenetic analysis further indicated that PsMV1 is a new member of the genus Mitovirus within the family Narnaviridae. This is the first report of the full-length nucleotide sequence of a novel mitovirus, PsMV1, from the causal agent of wheat stripe rust.

Soft Red and White Winter Wheat Response to Input‐Intensive Management

Core Ideas Prophylactic input applications failed to consistently increase wheat yield and net return without the presence of yield‐limiting factors. Traditional management significantly increased economic net return in three of four site‐years. Producers may wish to consider integrated pest management strategies for justification of input applications. Record grain yields and increased awareness of climate variability have more producers considering intensive (i.e., high‐input) wheat (Triticum aestivum L.) management. This study investigated soft winter wheat response to several agronomic inputs across intensive and traditional (i.e., low‐input) management systems. A four site‐year trial was established at Richville and Lansing, MI during 2015 and 2016 to evaluate the following inputs: increased rates of nitrogen (N) fertilizer, urease inhibitor (UI), nitrification inhibitor (NI), fungicide, plant growth regulator (PGR), and foliar micronutrients. Across four site‐years, intensive management did not increase yield compared to traditional management. In addition, traditional management increased average economic net return by $221 ha−1. At the reduced N rate, Richville 2016 yield decreased 0.94 Mg ha−1 within the intensive system suggesting greater N demand with intensive management. Due to significant stripe rust (Puccinia striiformis f. sp. tritici) occurrence, at 2016 Lansing, yield increased 0.75 Mg ha−1 when fungicide was added to the traditional system. Lansing 2017 yield decreased 0.52 Mg ha−1 when UI was removed from the intensive system, yet decreased 0.51 Mg ha−1 when UI was added to the traditional system. Heavy rainfall, lack of urea hydrolysis, and N rate likely contributed to the inconsistent UI response. The 2016 and 2017 growing seasons produced an overall absence of adverse environmental conditions which influenced negligible input responses. Although yield increases were observed, no single input increased net return. Results suggest intensive management benefits are unlikely at current wheat prices and without the presence of yield‐limiting factors.

KIRON INIA: TRIGO DE INVIERNO CON TOLERANCIA A SUELOS ACIDOS DEL SUR DE CHILE

‘Kiron INIA’ is a new wheat cultivar (Triticum aestivum L.) developed by the National Wheat Program at the Regional Experimental Center (CRI) Carillanca of the National Institute of Agricultural Research (INIA). The cultivar has medium plant height and late cycle; it is resistant to yellow rust (Puccinia striiformis West. f. sp. tritici Erikss) and oidium (Blumeria graminis D.C. f. sp. tritici Marchal), and moderately sensitive to leaf rust (Puccinia triticina f. sp. tritici Erikss y Henn) and septoria (Mycosphaerella graminicola (Fuckel) Sand). It is a high yielding winter wheat with good quality characteristics for direct baking, containing an allele of tolerance to soil acidity inherited from a parent. Its leaves are pale green, with a semi-erect flag leaf, with abundant cerosity (glaucosity) in the beam. The spike is white, decumbent, parallel in shape, high density, compact, with awns along its full length. The grain is round in shape, medium in size, and pale red in color. The height of the adult plant varies between 95 cm and 105 cm, with an average of 100 cm, and with a stem of very good resistance to lodging. It is a high yielding cultivar (12.9 t ha-1) exceeding the commercial check in different localities and seasons

Variation in Telial Formation of &lt;i&gt;Puccinia striiformis&lt;/i&gt; in the United States

Puccinia striiformis, the causal agent of stripe rust in wheat, barley, and various wild grasses, produces urediniospores and teliospores on these primary or auxiliary hosts. Telial formation, which stops producing infectious urediniospores, is affected by various host and environmental conditions. However, it is not clear if variation exists among different isolates in the United States. To determine the differences in the pathogen population, 1423 isolates collected in the United States from 2013 to 2016 were tested for telial formation in the seedling stage at a diurnal temperature profile of 4°C - 20°C. The percentages of telial formation varied greatly among the isolates. Of the 1423 isolates, 62.97% produced telia with the percentages of telial formation ranging from 1% to 95% under the test conditions. The formation of telia was significantly affected by the year and the month when the isolates were collected. The epidemiological regions or states, host plants (wheat, barley, and grasses), and races of the isolates did not significantly affect telial formation. However, significant effects on telial formation were observed by interactions between year and region, year and race, month and region and among year, month, and region, as well as between year and month. The results showed that telial formation is a complex trait under the genetic control of the pathogen isolates for adaptation to different environments. Further studies are needed to identify genes involved in the formation of telia and the relationship of telial formation to the survival, aggressiveness, fitness, and evolution of the pathogen.

Characterization of Yellow Rust (Puccinia striiformis) Resistance and Genetic Diversity in Nepalese Wheat Genotypes

Wheat (Triticum aestivum L.) is third important crop in Nepal after rice and maize. Yellow rust caused by Puccinia striiformis Westend. is a major disease of hills and adjoining foot hills. Both seedling and adult plant stage evaluations were carried out to characterize yellow rust resistance (Yr) genes in 105 Nepalese wheat genotypes at ICAR- Indian Wheat and Barley Research Institute, Regional Station, Shimla India. Eleven pathotypes of P. striiformis were used in seedling evaluation for identifying the resistance gene/s for yellow rust disease. Two most virulent and predominant pathotypes 78S84 and 46S119 were used to screen for adult plant resistance (APR). Four different resistance genes were inferred in tested material viz, YrA, Yr2, Yr9 and Yr27 by the seedling test. The postulated genes were observed either singly or in combination with other gene/s. The resistance genes YrA and Yr2 were detected alone whereas Yr27 was postulated in combination with Yr9. Among them, Yr9 was most dominant gene and was postulated in 48 genotypes either singly or in combination with Yr27. Twenty-one genotypes were found to confer low infection types (ITs) with hypersensitive and non-hypersensitive reaction against all the tested pathotypes. Twenty two of genotypes showed APR to both the pathotypes whereas 43 genotypes showed susceptibility to both pathotypes. In which 16 genotypes had susceptible response both seedling and Adult plant stage against both the pathotypes. Likewise, 53 genotypes had APR to one or other pathotype.

Grain quality in wheat—Impact of disease management

Abstract Winter wheat is commonly attacked by a range of major leaf diseases like septoria tritici blotch (Zymoseptoria tritici) (STB), yellow rust (Puccinia striiformis) (YR) and powdery mildew (Blumeria graminis) (PM), which have significant negative impacts on yields. Fungicides can mitigate these yield reductions and stabilize yields, mainly by helping to maintain green leaf area during grain filling. Trial data collected in the period 2007–2017 were analysed for links between disease control, yields and impact on grain quality parameters. The fungicides applied in this study were typically appropriate rates of mixtures of fungicides belonging to azoles, strobilurins and SDHIs and data represent different fungicide strategies carried out in different varieties, seasons and localities. Yield correlated positively to grain quality parameters such as thousand grain weight (TGW), specific weight (TW) and grain starch content (GSC). A negative correlation between yield and grain protein content (GPC) was found, while a strong positive correlation was measured between GPC and grain gluten content (GGC). Yield also correlated to % STB severity and % green leaf area (GLA). Overall, fungicide control strategies increased grain yields, TGW, TW and GSC significantly compared to untreated. No significant differences were measured between these parameters for three different strategies using either one or two treatments or treatments according to a decision support system. When treated and untreated plots were compared, a small but still significant reduction of GPC from 10.5% in untreated to 10.2% in fungicide treated plots was measured. Specific trials investigating impact from three dose rates of fungicides showed that full rate increased yield, TGW, TW and GSC significantly compared with the 25% of standard rate, while no significant differences for untreated and the three tested dose rates could be measured for GPC, GGC or grain moisture content (GMC). In four specifically analysed varieties with similar yields, TGW, GPC, GSC, TW and GMC were genotype specific and varied significantly between the four analysed varieties. In 57 trials with severe attack of either STB, YR or PM fungicides provided similar yield responses. Control of all three diseases reduced the GPC significantly. Control of YR and PM were found to have similar impacts on GPC, while STB had a steeper negative impact on GPC.

СРЕДИЗЕМНОМОРСКИЕ СТАРОМЕСТНЫЕ СОРТА ТВЕРДОЙ ПШЕНИЦЫ, СОХРАНЯЕМЫЕ В КОЛЛЕКЦИИ ВИР

Background . Landraces constitute a valuable pool for use in breeding. Even today, the collection of VIR contains this unique material, which has not been reproduced in the places of its origin for a long time, and for the most part does not occur in any collection of the world. About 60% of the landraces of the VIR durum wheat collection were collected in the countries of the Mediterranean basin where durum wheat is one of the leading cereals. Complex comparative study of this material according to its morphological and agrobiological traits makes it possible to identify valuable landraces and recommend them for the use in various studies. Objective. The research covered 313 landraces of durum wheat from 20 countries and regions of the Mediterranean basin preserved in the collection of VIR. The experiment was conducted in the fields of the Tel Hadiya Research Station of the International Center for Agricultural Research in the Dry Areas (ICARDA, Syria). Results and conclusion . As a result of the evaluation of economically useful traits, sources of earliness, short-stem characteristics, and productivity components were identified. The field assessment of resistance to the blotch of wheat (Septoria nodorum Belk.), wheat yellow rust (Puccinia striiformis West.) and wheat leaf rust (Puccinia recondita Rob. ex Desm. f. sp. tritici Erikss.) showed differences in the resistance to these diseases among landraces of different origin. Immunity to yellow rust was observed in the varieties from Algeria, Spain, Italy and Syria, to brown rust in the varieties from North Africa and Portugal, and to blotch in the varieties from Italy and Portugal. The studied durum wheat landraces possess valuable morphological characteristics. Identification of the Triticum durum Desf. accessions revealed new varieties and forms. An analysis of the results of the comparative study of the Mediterranean landraces manifested great diversity of their morphological characteristics and undoubted value of individual varieties possessing various important economic traits.

Antifungal Activities of Isoflavonoids from Uromyces striatus Infected Alfalfa.

Fungal pathogens constitute a severe yield-limiting factor for the pasture crop alfalfa (Medicago sativa L.). Eleven phenolic compounds, including a new isoflavane, were isolated from the Uromyces striatus Schroet. infected alfalfa. The effect of infection with U. striatus Schroet. on the phytochemical profile of alfalfa was investigated using ultra-performance liquid chromatography (UPLC), and the antifungal properties of isolated compounds against a range of pathogens were tested. It was found that the contents of most of the isolated compounds in U. striatus infected alfalfa were higher than those in healthy alfalfa. Compounds 1-5 exhibited a moderate inhibitory activity against Curvularia lunata with 40.14±1.63 %, 48.03±1.22 %, 57.54±1.18 %, 50.10±1.56 %, and 61.54±2.14 % inhibition ratio at the concentration of 50 μg/mL. Compounds 3 and 5 showed a weak inhibitory activity against Fusarium graminearum with the EC50 values of 104.2±2.66 and 123.0±1.23 μg/mL, and a moderate inhibitory activity against Bipolaris sorokinianum with the EC50 values of 39.1±2.05 and 95.0±1.01 μg/mL, respectively. In pot experiments with wheat, compounds 1-5 possessed desirable protective efficacy of over 80 % and curative effectiveness of over 50 % against Puccinia striiformis f. sp. tritici at a concentration of 0.5 mg/mL.

Histological and biochemical aspects of compatible and incompatible wheat- Puccinia striiformis interactions

The resistant, slow and fast-rusting cultivars were selected from 15 wheat cultivars to study biochemical and histological aspects of compatible and incompatible wheat-Puccinia striiformis interactions. Final rust severity (%) and area under disease progress curve were significantly decreased in resistant cultivars compared with susceptible ones. Biochemical analysis revealed that reactive oxygen species (ROS), i.e. superoxide (O2•-) and hydrogen peroxide (H2O2) significantly accumulated in the susceptible cultivars. While, activities of catalase (CAT), peroxidase (POX) and chlorophyll concentrations were increased in resistant cultivars. Histological examination using scanning and transmission electron microscope indicated that approximately all haustoria and hyphae were inhibited in resistant cultivar (Misr-1), development of haustorial mother cells and haustoria were retarded, and they were abnormal. On the other hand, large amounts of intercellular hyphae presented in the intercellular spaces and many haustoria were produced in fast-rusting cultivar (Sids-12). Nevertheless, a little of sours and spores on upper epidermis and in mesophyll tissue were observed in slow-rusting cultivar (Sakha-93)..

Pathotypic and molecular evolution of contemporary population of Puccinia striiformis f. sp. tritici in Egypt during 2016–2018

AbstractThe contemporary races of Puccinia striiformis f. sp. tritici (Pst) in Egypt during 2016–2018 were differentiated based on virulence and molecular patterns. Virulence patterns based on the reaction of the 17 World/European differential sets carrying stripe rust resistance genes (Yr genes) resulted in ten races including four new (first recorded in Egypt) and six old (previously recorded in Egypt). The new races were identified as 64E0 (virulence [V] Yr4, Su), 0E16 (V Yr8, 19), 66E0 (V Yr4, 7, 22, 23, Su) and 4E130 (V Yr2, 6, 7, 25, HVII), while the old were 0E0 (avirulence), 2E0 (V Yr7, 22, 23), 2E16 (V Yr7, 8, 19, 22, 23), 4E0 (V Yr2, 6), 6E4 (V Yr2, 6, 7, 22, 23, 25) and 70E4 (V Yr2, 4, 6, 7, 22, 23, 25, Su). Cluster analysis differentiated Pst races based on virulence frequency to Yr genes. Simple sequence repeat (SSR) markers were used to detect the molecular polymorphism of the Pst races. Clustering separated the old and new races into two groups, indicating their common ancestry since the new races were very distinct from the old races. Although clustering based on virulence revealed some evolutionary patterns, where the new races 64E0 and 66E0 may have probably evolved from the old races (2E16, 2E0, 6E4, 70E4) and the new race 4E130 may be evolved from the joint race 4E0. However, clustering based on molecular patterns indicated that the new races appear to be genetically distinct and may represent an exotic introduction rather than a mutation in isolates of the old races. A weak association between virulence and molecular patterns revealed that they are independent of each other. The SSR markers did not correspond to the virulences in the pathogen. Further studies on the potential virulence genes of the detected Pst virulences are needed.

Molecular and Cytogenetic Characterization of Six Wheat-Aegilops markgrafii Disomic Addition Lines and Their Resistance to Rusts and Powdery Mildew.

Aegilops markgrafii (Greuter) Hammer is an important source of genes for resistance to abiotic stresses and diseases in wheat (Triticum aestivum L.). A series of six wheat ‘Alcedo’-Ae. markgrafii chromosome disomic addition lines, designated as AI(B), AII(C), AIII(D), AV(E), AIV(F), and AVIII(G) carrying the Ae. markgrafii chromosomes B, C, D, E, F, and G, respectively, were tested with SSR markers to establish homoeologous relationships to wheat and identify markers useful in chromosome engineering. The addition lines were evaluated for resistance to rust and powdery mildew diseases. The parents Alcedo and Ae. markgrafii accession ‘S740-69’ were tested with 1500 SSR primer pairs and 935 polymorphic markers were identified. After selecting for robust markers and confirming the polymorphisms on the addition lines, 132 markers were considered useful for engineering and establishing homoeologous relationships. Based on the marker analysis, we concluded that the chromosomes B, C, D, E, F, and G belong to wheat homoeologous groups 2, 5, 6, 7, 3, and 4, respectively. Also, we observed chromosomal rearrangements in several addition lines. When tested with 20 isolates of powdery mildew pathogen (Blumeria graminis f. sp. tritici) from five geographic regions of the United States, four addition lines [AIII(D), AV(E), AIV(F), and AVIII(G)] showed resistance to some isolates, with addition line AV(E) being resistant to 19 of 20 isolates. The addition lines were tested with two races (TDBJ and TNBJ) of the leaf rust pathogen (Puccinia triticina), and only addition line AI(B) exhibited resistance at a level comparable to the Ae. markgrafii parent. Addition lines AII(C) and AIII(D) had been previously identified as resistant to the Ug99 race group of the stem rust pathogen (Puccinia graminis f. sp. tritici). The addition lines were also tested for resistance to six United States races (PSTv-4, PSTv-14, PSTv-37, PSTv-40, PSTv-51, and PSTv-198) of the stripe rust pathogen (Puccinia striiformis f. sp. tritici); we found no resistance either in Alcedo or any of the addition lines. The homoeologous relationships of the chromosomes in the addition lines, molecular markers located on each chromosome, and disease resistance associated with each chromosome will allow for chromosome engineering of the resistance genes.

Pathogenesis-related protein genes involved in race-specific all-stage resistance and non-race specific high-temperature adult-plant resistance to Puccinia striiformis f. sp. tritici in wheat

Interactions of the stripe rust pathogen (Puccinia striiformis f. sp. tritici) with wheat plants activate a wide range of host responses. Among various genes involved in the plant-pathogen interactions, the expressions of particular pathogenesis-related (PR) protein genes determine different defense responses. Different types of resistance have been recognized and utilized for developing wheat cultivars for resistance to stripe rust. All-stage resistance can be detected in seedling stage and remains at high levels throughout the plant growth stages. This type of resistance is race-specific and not durable. In contrast, plants with only high-temperature adult-plant (HTAP) resistance are susceptible in seedling stage, but become resistant when plants grow older and the weather becomes warmer. HTAP resistance controlled by a single gene is partial, but usually non-race specific and durable. The objective of this study was to analyze the expression of PR protein genes involved in different types of wheat resistance to stripe rust. The expression levels of 8 PR protein genes (PR1, PR1.2, PR2, PR3, PR4, PR5, PR9 and PR10) were quantitatively evaluated at 0, 1, 2, 7 and 14 days after inoculation in single resistance gene lines of wheat with all-stage resistance genes YrTr1, Yr76, YrSP and YrExp2 and lines carrying HTAP resistance genes Yr52, Yr59, Yr62 and Yr7B. Races PSTv-4 and PSTv-37 for compatible and incompatible interactions were used in evaluation of PR protein gene expression in wheat lines carrying all-stage resistance genes in the seedling-stage experiment while PSTv-37 was used in the HTAP experiment. Analysis of quantitative real-time polymerase chain reaction (qRT-PCR) revealed that all of the PR protein genes were involved in the different types of resistance controlled by different Yr genes. However, these genes were upregulated at different time points and at different levels during the infection process among the wheat lines with different Yr genes for either all-stage resistance or HTAP resistance. Some of the genes were also induced in compatible interactions, but the levels were almost always higher in the incompatible interaction than in the compatible interaction at the same time point for each Yr gene. These results indicate that both allsalicylic acid and jasmonate signaling pathways are involved in both race-specific all-stage resistance and non-race specific HTAP resistance. Although expressing at different stages of infection and at different levels, these PR protein genes work in concert for contribution to different types of resistance controlled by different Yr genes.

Antioxidant potential of barley genotypes inoculated with five different pathotypes of Puccinia striiformis f. sp. hordei.

The stripe rust caused by the fungal pathogen, Puccinia striiformis f. sp. hordei in barley (Hordeum vulgare L.) is a global problem that threatens the production of barley. The present study examined the disease reaction, free radical scavenging potential, non-enzymatic antioxidants like total phenols, o-dihydroxy phenols, flavonoids along with total chlorophyll, chlorophyll a, chlorophyll b and total carotenoids of the four barley genotypes viz. Jyoti (susceptible), RD2900, RD2901 and RD2552 (resistant) infected with five different pathotypes (M, G, 57, Q and 24) of P. striiformis f. sp. hordei. The disease reaction showing RD2901 in the category of immune to very resistant genotype followed by RD2552 in immune to resistant and RD2900 as moderately resistant and Jyoti as susceptible, which was well correlated with biochemical studies. RD2901 possessed higher antioxidant potential in terms of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·) scavenging activity, ferric reducing antioxidant power, reducing power and nitric oxide scavenging activity under control conditions and were maintained sufficiently high on inoculation with different pathotypes (M, G, 57, Q and 24) of P. striiformis f. sp. hordei. Further, these free radical scavenging activities showed the positive correlation with total phenols, o-dihydroxy phenols, flavonoids which in turn might be contributing in tolerance behaviour of this genotype. However, Jyoti with sensitive behaviour towards M, G, and 24 pathotypes depicted minimum DPPH activity and reducing power under control conditions.