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Worldwide food security is severely threatened by the devastating wheat stripe rust disease. The utilization of resistant wheat cultivars represents the most cost‐effective and efficient strategy for combating this disease. However, the lack of resistant resources has been a major bottleneck in breeding for wheat disease resistance. Therefore, revealing novel gene resources for combating stripe rust and elucidating the underlying resistance mechanism is of utmost urgency. In this study, we identified that the soybean NF‐YB transcription factor GmNF‐YB20 in wheat provides resistance to the stripe rust fungus (Puccinia striiformis f. sp. tritici, Pst). Wheat lines with stable overexpression of the GmNF‐YB20 enhanced resistance against multiple Pst races. Transcriptome profiling of GmNF‐YB20 transgenic wheat under Pst infection unveiled its involvement in the lipid signaling pathway. RT‐qPCR assays suggested that GmNF‐YB20 increased transcript levels of multiple nonspecific lipid transfer protein (LTP) genes during wheat‐Pst interaction, luciferase reporter analysis illustrates that it activates the transcription of TaLTP1.50 in wheat protoplast, and GmNF‐YB20 overexpressed wheat plants had higher total LTP content in vivo during Pst infection. Overexpression of TaLTP1.50 in wheat significantly increased resistance to Pst, whereas knockdown of TaLTP1.50 exhibited the opposite trends, indicating that TaLTP1.50 plays a positive role in wheat resistance. Taken together, our findings provide perspective regarding the molecular mechanism of GmNF‐YB20 in wheat and highlight the potential use for wheat breeding. Summary statement: The soybean transcription factor GmNF‐YB20 confers resistance to stripe rust in transgenic wheat by regulating nonspecific lipid transfer protein genes. Our findings provide perspective regarding the molecular mechanism of GmNF‐YB20 in wheat and highlight the potential use for wheat breeding. [ABSTRACT FROM AUTHOR]

SUMMARY: Plant fungal parasites manipulate host metabolism to support their own survival. Among the many central metabolic pathways altered during infection, the glyoxylate cycle is frequently upregulated in both fungi and their host plants. Here, we examined the response of the glyoxylate cycle in bread wheat (Triticum aestivum) to infection by the obligate biotrophic fungal pathogen Puccinia striiformis f. sp. tritici (Pst). Gene expression analysis revealed that wheat genes encoding the two unique enzymes of the glyoxylate cycle, isocitrate lyase (TaICL) and malate synthase, diverged in their expression between susceptible and resistant Pst interactions. Focusing on TaICL, we determined that the TaICL B homoeolog is specifically upregulated during early stages of a successful Pst infection. Furthermore, disruption of the B homoeolog alone was sufficient to significantly perturb Pst disease progression. Indeed, Pst infection of the TaICL‐B disruption mutant (TaICL‐BY400*) was inhibited early during initial penetration, with the TaICL‐BY400* line also accumulating high levels of malic acid, citric acid, and aconitic acid. Exogenous application of malic acid or aconitic acid also suppressed Pst infection, with trans‐aconitic acid treatment having the most pronounced effect by decreasing fungal biomass 15‐fold. Thus, enhanced TaICL‐B expression during Pst infection may lower accumulation of malic acid and aconitic acid to promote Pst proliferation. As exogenous application of aconitic acid and malic acid has previously been shown to inhibit other critical pests and pathogens, we propose TaICL as a potential target for disruption in resistance breeding that could have wide‐reaching protective benefits for wheat and beyond. Significance Statement: Isocitrate lyase (ICL) is a unique enzyme of the glyoxylate cycle that frequently accumulates in fungi and their host plants. We uncovered a critical role for wheat ICL in supporting Puccinia striiformis f. sp. tritici (Pst) infection. Disruption of ICL function in wheat prevented Pst disease progression, likely due to the accumulation of glyoxylate cycle intermediates that can suppress Pst infection. ICL thus represents a new potential target for disruption in resistance breeding. [ABSTRACT FROM AUTHOR]

The dynamic balance and distribution of sphingolipid metabolites modulate the level of programmed cell death and plant defence. However, current knowledge is still limited regarding the molecular mechanism underlying the relationship between sphingolipid metabolism and plant defence. In this study, we identified a wheat RNA‐binding protein 1 (TaRBP1) and TaRBP1 mRNA accumulation significantly decreased in wheat after infection by Puccinia striiformis f. sp. tritici (Pst). Knockdown of TaRBP1 via virus‐induced gene silencing conferred strong resistance to Pst by enhancing host plant reactive oxygen species (ROS) accumulation and cell death, indicating that TaRBP1 may act as a negative regulator in response to Pst. TaRBP1 formed a homopolymer and interacted with TaRBP1 C‐terminus in plants. Additionally, TaRBP1 physically interacted with TaGLTP, a sphingosine transfer protein. Knockdown of TaGLTP enhanced wheat resistance to the virulent Pst CYR31. Sphingolipid metabolites showed a significant accumulation in TaGLTP‐silenced wheat and TaRBP1‐silenced wheat, respectively. In the presence of the TaRBP1 protein, TaGLTP failed to be degraded in a 26S proteasome‐dependent manner in plants. Our results reveal a novel susceptible mechanism by which a plant fine‐tunes its defence responses by stabilizing TaGLTP accumulation to suppress ROS and sphingolipid accumulation during Pst infection. [ABSTRACT FROM AUTHOR]

Although Blufensins (Bln) have important functions in the response of plants to biotic stress the precise functioning of Bln in wheat remains largely unknown. Here we isolated a Bln gene (TaBln4) from Suwon 11 infected by Puccinia striiformis f. sp. tritici (Pst). Expression of TaBln4 increased in host plants at the early stage of infection with a virulent Pst race (CYR31) but was unchanged in response to infection by an avirulent race (CYR23). Transcription levels of TaBln4 were also regulated by hormone and abiotic stresses. Expression of TaBln4 in tobacco leaves suppressed Bax-induced programmed cell death. Knockdown of TaBln4 by virus-induced gene silencing inhibited colonization of race CYR31 by increasing the accumulation of H2O2 and formation of hypersensitive responses (HR). Transient overexpression of TaBln4 by a transient overexpression system (BSMV-VOX) increased the susceptibility of wheat to CYR31. Results from bimolecular fluorescence complementation and pull-down assays demonstrated that TaBLN4 interacted with calmodulin. Taken together, our results suggest that TaBln4 negatively regulates resistance in wheat to Pst in a reactive oxygen species (ROS)- and HR-dependent manner.

Puccinia striiformis Westend. f. sp. tritici (Pst) pathotype CYR34 is widely virulent and prevalent in China. Here, we report identification of a strpie rust resistance (Yr) gene, designated Yr041133, in winter wheat line 041133. This line produced a hypersensitive reaction to CYR34 and conferred resistance to 13 other pathotypes. Resistance to CYR34 in line 041133 was controlled by a single dominant gene. Bulked segregant RNA sequencing (BSR-Seq) was performed on a pair of RNA bulks generated by pooling resistant and susceptible recombinant inbred lines. Yr041133 was mapped to a 1.7 cM genetic interval on the chromosome arm 7BL that corresponded to a 0.8 Mb physical interval (608.9–609.7 Mb) in the Chinese Spring reference genome. Based on its unique physical location Yr041133 differred from the other Yr genes on this chromosome arm.

SUMMARY: Puccinia striiformis f. sp. tritici (Pst), the causal agent of stripe rust, is a destructive pathogen of Triticum aestivum (wheat), threatening wheat production worldwide. Pst delivers hundreds of effectors to manipulate processes in its hosts during infection. The SGT1 (suppressor of the G2 allele of skp1), RAR1 (required for Mla12 resistance) and HSP90 (heat‐shock protein 90) proteins form a chaperone complex that acts as a core modulator in plant immunity. However, little is known about how Pst effectors target this immune component to suppress plant immunity. Here, we identified a Pst effector PstSIE1 that interacts with TaSGT1 in wheat and is upregulated during the early infection stage. Transient expression of PstSIE1 suppressed cell death in Nicotiana benthamiana induced by VmE02 and PcNLP2. Transgenic expression of PstSIE1‐RNAi constructs in wheat significantly reduced the virulence of Pst. Overexpression of PstSIE1 in wheat increased the number of rust pustules and reduced the accumulation of reactive oxygen species (ROS), indicating that PstSIE1 functions as an important pathogenicity factor in Pst. PstSIE1 was found to compete with TaRAR1 to bind TaSGT1, thus disrupting the formation of the TaRAR1–TaSGT1 subcomplex. Taken together, PstSIE1 is an important Pst effector targeting the immune component TaSGT1 and involved in suppressing wheat defense. Significance Statement: PstSIE1 is an important Pst effector targeting the immune component TaSGT1 and involved in suppressing wheat defense. This work broadens our understanding of how the molecular mechanisms of fungal effectors suppress plant immunity. [ABSTRACT FROM AUTHOR]

A biotrophic fungus, Puccinia striiformis f.sp. tritici (Pst), which causes stripe rust disease in wheat is the most yield-limiting factor in wheat production. Plants have complex defense mechanisms against invading pathogens. Hypersensitive response (HR), a kind of programmed cell death (PCD) at the infection site, is among these defense mechanisms. Transcription factors (TFs) play a crucial role in plant defense response against invading pathogens. Myeloblastosis (MYB) TFs are among the largest TFs families that are involved in response to both biotic and abiotic stresses. However, little is known about the mechanisms of MYB TFs during the interaction between wheat and the stripe rust fungus. Here, we identified an R2R3 MYB TF from wheat, designated as TaMYB391, and characterized its functional role during wheat–Pst interaction. Our data indicated that TaMYB391 is induced by Pst infection and exogenous application of salicylic acid (SA) and abscisic acid (ABA). TaMYB391 is localized in the nucleus of both wheat and Nicotiana benthamiana. Transient overexpression of TaMYB391 in N. benthamiana triggered HR-related PCD accompanied by increased electrolyte leakage, high accumulation of reactive oxygen species (ROS), and transcriptional accumulation of SA defense-related genes and HR-specific marker genes. Overexpression of TaMYB391 in wheat significantly enhanced wheat resistance to stripe rust fungus through the induction of pathogenesis-related (PR) genes, ROS accumulation and hypersensitive cell death. On the other hand, RNAi-mediated silencing of TaMYB391 decreased the resistance of wheat to Pst accompanied by enhanced growth of the pathogen. Together our findings demonstrate that TaMYB391 acts as a positive regulator of HR-associated cell death and positively contributes to the resistance of wheat to the stripe rust fungus by regulating certain PR genes, possibly through SA signaling pathways. [ABSTRACT FROM AUTHOR]

Stripe rust disease is caused by the fungus Puccinia striiformis f. sp. tritici and severely threatens wheat worldwide, repeatedly breaking resistance conferred by resistance genes and evolving more aggressive strains. Wild emmer wheat, Triticum dicoccoides, is an important source for novel stripe rust resistance (Yr) genes. Yr15, a major gene located on chromosome 1BS of T. dicoccoides, was previously reported to confer resistance to a broad spectrum of stripe rust isolates, at both seedling and adult plant stages. Introgressions of Yr15 into cultivated T. aestivum bread wheat and T. durum pasta wheat that began in the 1980s are widely used. In the present study, we aimed to validate SSR markers from the Yr15 region as efficient tools for marker-assisted selection (MAS) for introgression of Yr15 into wheat and to compare the outcome of gene introgression by MAS and by conventional phenotypic selection. Our findings establish the validity of MAS for introgression of Yr15 into wheat. We show that the size of the introgressed segment, defined by flanking markers, varies for both phenotypic selection and MAS. The genetic distance of the MAS marker from Yr15 and the number of backcross steps were the main factors affecting the length of the introgressed donor segments. Markers Xbarc8 and Xgwm493, which are the nearest flanking markers studied, were consistent and polymorphic in all 34 introgressions reported here and are therefore the most recommended markers for the introgression of Yr15 into wheat cultivars. Introgression directed by markers, rather than by phenotype, will facilitate simultaneous selection for multiple stripe rust resistant genes and will help to avoid escapees during the selection process.

Bread wheat (Triticum aestivum L.) is one of the most important cereals in the world, its production in recent years was affected by yellow rust (RA), caused by the Puccinia striiformis f. sp. tritici fungus. Planting resistant varieties has allowed to counteract the effects of the disease in some parts of the world. Adult plants of the Mexican variety Huites F95 bread wheat have shown resistance to yellow rust (RPA) since their release. The hypothesis of this study was that minor genes confer resistance to yellow rust in the Huites F95 variety. The objective was to determine the type of resistance and estimate the number of genes that condition it. To that end, a population of 198 recombinant inbred lines (RIL) was generated by crossing Huites F95 and Avocet-YrA. The phenotypic characterization was carried out in Toluca, Mexico State, in the Spring-Summer cycles of 2013, 2014 and 2015, and in El Batán, Texcoco, Mexico State, during Spring-Summer 2015. Artificial epidemics were created using a mixture of MEX96.11, MEX08.13, CMEX14.25 and MEX14.191 races of P. striiformis f. sp. tritici. Temperature and humidity were favorable for the development of the disease in the four evaluation environments. The resistance of Huites F95 to RA was found to be quantitative and caused by the effect of minor genes. The X² analysis indicated the presence of four to five genes that confer RPA to yellow rust. Huites F95 does not have race-specific resistance to the races evaluated, but the adult plant has high resistance to several races in the main wheat regions of the country, and it is a parent that can be incorporated into global breeding programs and contribute to achieving durable resistance to yellow rust. [ABSTRACT FROM AUTHOR]

Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) is a devastating foliar disease that affects common wheat and barley throughout the world. The reasonable deployment of adult plant resistance (APR) wheat varieties is one of the best methods for controlling this disease. Wheat landraces are valuable resources for identifying the genes/QTLs responsible for disease resistance. Humai 15 is a Chinese spring wheat landrace and it has exhibited adequate levels of APR to the prevalent Pst races in field environments for many years. In this study, a population of 177 recombinant inbred lines (RILs) was derived from Humai 15 × Mingxian 169. After screening based on a 90K chip array using 45 RILs and Kompetitive Allelic Specific PCR marker genotyping for the population of RILs, a major effect QTL in Humai 15 was located on the centromere of chromosome 2B, where it accounted for up to 47.2% of the phenotypic variation. Two other minor QTL genes from Humai 15 were located on chromosome arms 3BS and 4BL. The Yr18 gene was identified on chromosome arm 7DS in Mingxian 169.

Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) is a devastating foliar disease that affects common wheat and barley throughout the world. The reasonable deployment of adult plant resistance (APR) wheat varieties is one of the best methods for controlling this disease. Wheat landraces are valuable resources for identifying the genes/QTLs responsible for disease resistance. Humai 15 is a Chinese spring wheat landrace and it has exhibited adequate levels of APR to the prevalent Pst races in field environments for many years. In this study, a population of 177 recombinant inbred lines (RILs) was derived from Humai 15 × Mingxian 169. After screening based on a 90K chip array using 45 RILs and Kompetitive Allelic Specific PCR marker genotyping for the population of RILs, a major effect QTL in Humai 15 was located on the centromere of chromosome 2B, where it accounted for up to 47.2% of the phenotypic variation. Two other minor QTL genes from Humai 15 were located on chromosome arms 3BS and 4BL. The Yr18 gene was identified on chromosome arm 7DS in Mingxian 169. [ABSTRACT FROM AUTHOR]

We examined the commercial life cycle of varieties of arable crops that could bring a better understanding of the drivers of their commercial success. In the current study, we propose indicators to describe the commercial life cycle of a variety and test their relevance on a case study centered on bread wheat varieties in France. We focus on yellow (stripe) rust, caused by Puccinia striiformis Westend. f. sp. tritici Eriks., an important disease that led to the rapid withdrawal from the French market of susceptible varieties during the last decades. In the present study, we assess how yellow rust pressure influenced the commercial life cycle of 31 bread wheat varieties over the period 1987–1991 which was characterized by the breakdown of resistance based on two race-specific genes Yr6 and Yr9 . We defined areas of bread wheat production located in the northern half of France based on homogeneity for yellow rust pressure, virulence frequencies, varietal composition and varietal replacement. We identified four groups of non-redundant indicators and retained one indicator per group based on its biological relevance when considering a priori hypotheses on the influence of yellow rust epidemics on the commercial life cycle of susceptible varieties. These four indicators describe the commercial life-cycle duration, the growth phase duration, the coincidence between an epidemic peak and the end of the growth phase, and the cumulative percentages of acreage of the variety during the growth phase duration. For each homogeneous production area, we calculated these four indicators for a set of varieties and performed a principal component analysis associated with a clustering algorithm. In the northwest coastline production area, known to be highly affected by yellow rust, we identify eight varieties presenting a combination of indicator values suggesting a rapid withdrawal from the market. All these varieties were susceptible to yellow rust, among which five were concerned by the breakdown of resistance based on Yr6 or Yr9 race-specific gene. In contrast, in the northeast production area, much less affected by yellow rust over the period studied, no variety presented a combination of indicator values related to a rapid withdrawal. Beyond the identification of susceptible varieties, our statistical procedure has also permitted to highlight two varieties, Soissons and Scipion, with potential durable resistance in the northwest coastline production area. A promising perspective for breeders could be a more complete identification of varieties with durable resistance that could promote the long-term durability of yellow rust control to face future epidemics. [ABSTRACT FROM AUTHOR]

Actin filament assembly in plants is a dynamic process, requiring the activity of more than 75 actin-binding proteins. Central to the regulation of filament assembly and stability is the activity of a conserved family of actin-depolymerizing factors ( ADFs), whose primarily function is to regulate the severing and depolymerization of actin filaments. In recent years, the activity of ADF proteins has been linked to a variety of cellular processes, including those associated with response to stress. Herein, a wheat ADF gene, Ta ADF4, was identified and characterized. Ta ADF4 encodes a 139-amino-acid protein containing five F-actin-binding sites and two G-actin-binding sites, and interacts with wheat ( Triticum aestivum) Actin1 (Ta ACT1), in planta. Following treatment of wheat, separately, with jasmonic acid, abscisic acid or with the avirulent race, CYR23, of the stripe rust pathogen Puccinia striiformis f. sp. tritici, we observed a rapid induction in accumulation of Ta ADF4 mRNA. Interestingly, accumulation of Ta ADF4 mRNA was diminished in response to inoculation with a virulent race, CYR31. Silencing of Ta ADF4 resulted in enhanced susceptibility to CYR23, demonstrating a role for Ta ADF4 in defense signaling. Using a pharmacological-based approach, coupled with an analysis of host response to pathogen infection, we observed that treatment of plants with the actin-modifying agent latrunculin B enhanced resistance to CYR23, including increased production of reactive oxygen species and enhancement of localized hypersensitive cell death. Taken together, these data support the hypothesis that Ta ADF4 positively modulates plant immunity in wheat via the modulation of actin cytoskeletal organization. [ABSTRACT FROM AUTHOR]

The gene, designated TaMADS2, was obtained from wheat leaves infected with the wheat stripe rust fungus by in silico cloning and RT-PCR. TaMADS2 encodes a predicted 159-amino-acid polypeptide that contains a highly conserved MADS domain. Phylogenetic analysis revealed that TaMADS2 is a type I MADS-box gene. The TaMADS2 transcript was detected in wheat leaves, stems, and roots. The expression of TaMADS2 was substantially down-regulated in the compatible interaction between wheat and Puccinia striiformis f. sp. tritici (Pst) at 36 and 48 h post-inoculation (hpi), whereas in the incompatible interaction the down-regulation was only observed at 48 hpi. Exogenous salicylic acid (SA) and abscisic acid (ABA) greatly induced the expression of TaMADS2 at 12 h post treatment (hpt), whereas methyl jasmonate (MeJA) down-regulated TaMADS2 at 6 hpt by approximately two-fold.

Expressed sequenced tags containing simple sequence repeats (EST-SSRs) were used to identify molecular markers associated with yellow rust resistance in wheat (Triticum aestivum L.). A cross between yellow rust resistant (PI178383) and susceptible (Harmankaya99) wheat genotypes was performed and respective DNA pools from the resistant and susceptible F2 seedlings were constructed. 78 EST-SSR primers were used for bulked segregant analysis and one EST-SSR marker (Pk54), identified as 200 bp fragment, was present in the resistant parent and resistant F2 hybrids but not in the susceptible ones. 108 wheat genotypes differing in yellow rust resistance were screened with Pk54 and 68 % of the wheat genotypes, known to be yellow rust resistant, had the Pk54 marker, further suggesting that the presence of this marker correlates with yellow rust resistance.

Stripe rust of winter bread wheat ( Triticum aestivum L.) causes substantial grain yield loss in Central Asia. This study involved two replicated field experiments undertaken in 2009-2010 and 2010-2011 winter wheat crop seasons. The first experiment was conducted to determine grain yield reductions on susceptible winter wheat cultivars using single and two sprays of fungicide at Zadoks growth stages Z61-Z69 in two farmers' fields in Tajikistan and one farmer's field in Uzbekistan. In the second experiment, four different fungicides at two concentrations were evaluated at Zadoks growth stage Z69. These included three products from BASF - Opus (0.5 l/ha and 1.0 l/ha), Platoon (0.5 l/ha and 1.0 l/ha) and Opera (0.75 l/ha and 1.5 l/ha) - and locally used fungicide Titul 390 (0.5 l/ha and 1.0 l/ha). One and two sprays of fungicides did not differ significantly (P > 0.05) in increasing grain yield. Stripe rust reduced grain yield and 1000-kernel weight ( TKW) from 24 to 39% and from 16 to 24%, respectively. The benefits from the two concentrations of the same fungicide did not consistently resulted in significantly higher grain yield, suggesting that the lower concentrations could be more cost effective. Our study provides important information about the selection of fungicides, spray concentrations and number of spray to control stripe rust and increase grain yield. The findings could play an important role in developing stripe rust management approaches such as fungicide rotation and strategic fungicide applications in Central Asian countries. [ABSTRACT FROM AUTHOR]

Tyrosine phosphorylation protein A (TypA/BipA) belongs to the ribosome-binding GTPase superfamily. In many bacterial species, TypA acts as a global stress and virulence regulator and also mediates resistance to the antimicrobial peptide bactericidal permeability-increasing protein. However, the function of TypA in plants under biotic stresses is not known. In this study, we isolated and functionally characterized a stressresponsive TypA gene (TaTypA) from wheat, with three copies located on chromosomes 6A, 6B, and 6D, respectively. Transient expression assays indicated chloroplast localization of TaTypA. The transcript levels of TaTypA were up-regulated in response to treatment with methyl viologen, which induces reactive oxygen species (ROS) in chloroplasts through photoreaction, cold stress, and infection by an avirulent strain of the stripe rust pathogen. Knock down of the expression of TaTypA through virusinduced gene silencing decreased the resistance of wheat to stripe rust accompanied by weakened ROS accumulation and hypersensitive response, an increase in TaCAT and TaSOD expression, and an increase in pathogen hyphal growth and branching. Our findings suggest that TaTypA contributes to resistance in an ROS-dependent manner. [ABSTRACT FROM AUTHOR]

Stripe rust of wheat (Triticum aestivum), caused byPuccinia striiformisf. sp.tritici, is highly affected by temperature, but the role of crop canopy temperature in stripe rust resistance is poorly understood. Five wheat varieties, which have different canopy temperatures and are susceptible toP. striiformisf. sp.triticiat the seedling stage, were investigated for resistance to stripe rust at the adult-plant stage in greenhouse and field experiments. In the greenhouse tests, all five varieties were resistant to stripe rust at the adult-plant stage. At the grain-filling stage in the 2007–2010 field experiments at two locations, the two varieties (NR 9405 and 9430) with higher canopy temperatures had lower disease index and smaller area under the disease progress curve values than the three varieties (Shaan 229, RB 6 and Xiaoyan 6) with lower canopy temperatures. The results indicated that the five tested wheat varieties had similar resistance reactions to stripe rust at the adult-plant stage in the greenhouse experiment, but showed different levels of resistance under natural infection conditions in the field. The negative correlation between canopy temperature and disease index during the grain-filling stage was significant. Thus, high wheat canopy temperatures provide unfavourable conditions for the development of stripe rust. This study is helpful for further developing an ecological approach for reducing stripe rust damage. [ABSTRACT FROM AUTHOR]

Stripe rust (or yellow rust), caused by Puccinia striiformis f. sp. tritici ( Pst), is a devastating fungal disease of common wheat. Wheat line P9897 showed adult-plant resistance (APR) to stripe rust for several years. To map resistance quantitative trait loci (QTL), F lines from a cross of P9897 with susceptible Mingxiang 169 were phenotyped for stripe rust response in replicated field trials in 2013. Resistance gene analog polymorphism and simple sequence repeat markers were used to identify markers linked to the resistance QTL. Two QTL, QYr.nafu- 2BL and QYr.nafu- 3BS conferring APR to stripe rust, were mapped to 8.8 and 3.3 cM intervals on chromosome 2BL and 3BL, respectively. QYr.nafu- 2BL is likely a new APR gene for resistance to stripe rust, and QYr.nafu- 3BS is likely the same locus as previously identified QYr.uga- 3BS.1. These QTL with linked markers could be used in developing wheat cultivars with stripe rust resistance. [ABSTRACT FROM AUTHOR]

Yellow (or stripe) rust, caused by Puccinia striiformis f. sp. tritici ( Pst), is an important wheat disease worldwide. The development of wheat cultivars with adult plant resistance (APR) has been given increasing emphasis in recent years because of the reputed durability of APR compared to all-stage resistance. Wheat landrace Caoxuan 5 showed a high level of APR in field nurseries from 2008 to 2014. Bulked segregant analysis using resistance gene analog polymorphism, simple sequence repeat and sequence-tagged site markers identified molecular markers linked to resistance genes. A total of 176 F lines were evaluated for stripe rust response in field nurseries at two sites for 2 years. Broad sense heritability of APR in the population was estimated as 0.81. Inclusive composite interval mapping identified quantitative trait loci (QTL) QYrcx.nafu- 3BS and QYrcx.nafu- 6AL conferring adult plant resistance and they explained 17.3-38.1 % and 9.7-19.8 % of the phenotypic variations, respectively. Based on molecular markers, both QTL appear to be different from previously identified stripe rust resistance genes. The resistance QTL and their molecular markers identified in Caoxuan 5 should be useful in breeding for stripe rust resistance. [ABSTRACT FROM AUTHOR]

The actin cytoskeleton is involved in plant defense responses; however, the role of the actin-depolymerizing factor (ADF) family, which regulates actin cytoskeletal dynamics, in plant disease resistance, is largely unknown. Here, we characterized a wheat ( Triticum aestivum) ADF gene, TaADF7, with three copies located on chromosomes 1A, 1B, and 1D, respectively. All three copies encoded the same protein, although there were variations in 19 nucleotide positions in the open reading frame. Transcriptional expression of the three TaADF7 copies were all sharply elevated in response to avirulent Puccinia striiformis f. sp. tritici ( Pst) infection, with similar expression patterns. TaADF7 regulated the actin cytoskeletal dynamics by targeting the actin cytoskeleton to execute actin binding/severing activities. When the TaADF7 copies were all silenced by virus-induced gene silencing, the growth of Pst hypha increased and sporadic urediniospores were observed, as compared with control plants, upon inoculation with avirulent Pst. In addition, the accumulation of reactive oxygen species (ROS) and the hypersensitive response (HR) were greatly weakened, whereas cytochalasin B partially rescued the HR in TaADF7 knock-down plants. Together, these findings suggest that TaADF7 is likely to contribute to wheat resistance against Pst infection by modulating the actin cytoskeletal dynamics to influence ROS accumulation and the HR. [ABSTRACT FROM AUTHOR]

Stripe rust (caused by Puccinia striiformis f. sp. tritici) of wheat (Triticum aestivum) is a devastating disease in temperate regions when susceptible varieties are grown and environmental conditions sustain high disease pressures. With frequent and severe outbreaks, disease resistance is a key tool for controlling stripe rust on wheat. The goal of this research was to identify quantitative trait loci (QTL) involved in stripe rust resistance from the important US Pacific Northwest soft white winter wheat varieties “Eltan” and “Finch”. An F2:5 recombinant inbred line (RIL) mapping population of 151 individuals derived from the Finch × Eltan cross was developed through single seed descent. A linkage map comprising 683 unique single nucleotide polymorphism (SNP) loci and 70 SSR markers were used to develop 22 linkage groups consisting of 16 of the 21 chromosomes. Stripe rust data were collected on the RILs during the summers of 2012 to 2014. QTL analysis identified two genomic regions on chromosomes 4A (QYrel.wak-4A) and 6B (QYrfi.wak-6B) associated with resistance from Eltan and Finch, respectively. The results of the QTL analysis showed that QYrel.wak-4A and QYrfi.wak-6B reduced infection type and disease severity. Based upon both molecular and phenotypic differences, QYrel.wak-4A is a novel QTL for adult plant resistance (APR) to stripe rust.

The gene, designated TaMADS2, was obtained from wheat leaves infected with the wheat stripe rust fungus by in silico cloning and RT-PCR. TaMADS2 encodes a predicted 159-amino-acid polypeptide that contains a highly conserved MADS domain. Phylogenetic analysis revealed that TaMADS2 is a type I MADS-box gene. The TaMADS2 transcript was detected in wheat leaves, stems, and roots. The expression of TaMADS2 was substantially down-regulated in the compatible interaction between wheat and Puccinia striiformis f. sp. tritici ( Pst) at 36 and 48 h post-inoculation (hpi), whereas in the incompatible interaction the down-regulation was only observed at 48 hpi. Exogenous salicylic acid (SA) and abscisic acid (ABA) greatly induced the expression of TaMADS2 at 12 h post treatment (hpt), whereas methyl jasmonate (MeJA) down-regulated TaMADS2 at 6 hpt by approximately two-fold. [ABSTRACT FROM AUTHOR]

High grain yield and resistance to stripe (yellow) rust are the most important traits for successful adoption of winter wheat varieties in Central and West Asia. This study was conducted to determine the stripe rust response and agronomic performance of a set of breeding lines recently developed by the International Winter Wheat Improvement Program (IWWIP). Replicated field studies were conducted in 2010 and 2011 using 38 experimental lines, one regional check (Konya) and one local check. Stripe rust scores were recorded at Karshi, Uzbekistan, and Karaj and Mashhad, Iran, in 2010. Grain yield was recorded at two sites each in Uzbekistan (Karshi and Kibray) and Iran (Karaj and Mashhad) and one site in Turkey (Eskisehir). The test lines showed variation for stripe rust severity, grain yield, 1,000-kernel weight, days to heading and plant height. Several stripe rust resistant genotypes were either higher yielding or equal to the local checks at different sites. Based on stripe rust resistance and yield performance in 2010, a set of 16 genotypes was selected and evaluated in 2011. All 16 were resistant at Almaty, Kazakhstan, and Dushanbe, Tajikistan, in 2011, whereas 9 of the 16 were resistant at Terter, Azerbaijan. The genotypes 'TCI-02-138, 'Solh', 'CMSS97M00541S', 'TCI -2-88(A)' and 'TCI-02-88(C)' were consistently resistant to stripe across all sites in both years. Several lines showed high grain yields and superior agronomic performance across four sites in Uzbekistan and one site in Tajikistan. One genotype has been released in Uzbekistan and another in Tajikistan. [ABSTRACT FROM AUTHOR]

Abstract: Endophytic Bacillus subtilis strain E1R-j, isolated from wheat roots, inhibits a wide range of microorganisms. In this study, we determined its inhibitory effect on urediniospore germination of Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat stripe rust and biocontrol effect on the rust development using bacterial cell suspension (BCS) and fermentation liquid with and without bacterial cells (FLBC and FL). Urediniospore germination was significantly inhibited by all three formulations in vitro. The maximum inhibition rate was 84.1% treated with the 10-fold dilution of original formulation of FLBC. Microscopic observation revealed that the bacterial treatments caused urediniospores and germ tubes ruptured, which resulted in protoplasm release and dysfunction of fungal structures. Urediniospore germination was also significantly inhibited by spraying E1R-j on leaf surface before inoculation. Formulations FLBC and FL were both better than formulation BCS. In a condition-controlled greenhouse, application of FLBC and FL 24 and 0 h before Pst inoculation displayed a protective mode in reducing disease severity, and the control efficacy was between 54.0% and 87.7%. For formulation BCS, only the application of 24 h before Pst inoculation significantly reduced rust severity with control efficacy 51.8%. The incidence of diseased leaves in the treatments of FLBC and FL were significantly reduced compared to the non-treated plots in the field experiments conducted in the season 2007–2008. The control efficacy was 51% and 43% for the two treatments, respectively. This study is helpful for further developing a biocontrol approach for managing stripe rust. [Copyright &y& Elsevier]

In China, wheat stripe rust, caused by Puccinia s triiformis f. sp. tritici, is one of the most destructive diseases of wheat. The Longnan and Linxia regions in Gansu Province and Qinghai Province are the major over-summering regions for the pathogen and key epidemiological zones in Northwest China. Population genetic diversity and interregional long-distance spread of the wheat stripe rust pathogen in Northwest China were studied using SSR markers. The genetic diversity in the Longnan population was much higher than those in the Linxia and Qinghai populations. Therefore, the molecular data confirmed that the Longnan region is a center of genetic diversity for P. striiformis f. sp. tritici in Northwest China. The low genetic differentiation ( Gst = 0.15) and the extensive gene flow ( Nm = 1.37) were found among the three regions in Northwest China. The most important conclusion of this study is that the stripe rust inoculum in Qinghai can come from both Longnan and Linxia, but mainly from Longnan directly in the spring. [ABSTRACT FROM AUTHOR]

Plants exhibit resistance to incompatible pathogens by localized and systemic defense responses. In this study, a proteomics approach was used to study compatible and incompatible interactions between wheat and Puccinia striiformis f. sp. tritici ( Pst) . Seedlings of wheat cv. Suwon 11 were inoculated with isolates of compatible race CYR31 and incompatible race CYR23. Total proteins isolated from wheat leaves were separated by two-dimensional gel electrophoresis. Compared with the mock inoculation, 41 differentially expressed proteins at 24 and 72 h post-inoculation were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and 23 of these proteins were positively identified. Of those, six were further examined for changes at the transcriptional level in wheat leaves infected with Pst. They were categorized into classes related to photosynthesis, antioxidant defense, signal transduction, and metabolism. Annotation of proteins induced in incompatible interactions revealed a rapid resistance response that included the induction of protein kinase signaling and the production of reactive oxygen species, which usually occur during R-gene-mediated responses. Proteins with antioxidant functions, e.g., ascorbate peroxidase, dehydroascorbate reductase, and glutathione S-transferase, were differentially expressed between compatible and incompatible interactions, indicating differential accumulation of reactive oxygen species in infected tissues. In addition, fragments of ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) were identified in proteins isolated from Pst-infected leaves. Rubisco fragmentation in response to Pst inoculation was confirmed by western blot analysis, indicating that chloroplasts and photosynthesis in both the incompatible and compatible situations were affected by Pst infection. [ABSTRACT FROM AUTHOR]

Wheat is the most important cereal in Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan) and the Caucasus (Armenia, Azerbaijan and Georgia). Stripe rust, caused by Puccinia striiformis f. sp. tritici is considered the most important disease of wheat in Central Asia and the Caucasus (CAC). Although stripe rust has been present in the region for a long time, it has become a serious constraint to wheat production in the past 10 years. This is reflected by the occurrence of five epidemics of stripe rust in the CAC region since 1999, the most recent in 2010. Several wheat varieties occupying substantial areas are either susceptible to stripe rust or possess a low level of resistance. Information on the stripe rust pathogen in terms of prevalent races and epidemiology is not readily available. Furthermore, there is an insufficient understanding of effective stripe rust resistance genes in the region, and little is known about the resistance genes present in the commercial varieties and advanced breeding lines. The deployment of resistant varieties is further complicated by putative changes in virulence in the pathogen population in different parts of the CAC. Twenty four out of 49 improved wheat lines received through international nurseries or other exchange programs showed high levels of resistance to stripe rust to local pathogen populations in 2009. Fifteen of the 24 stripe rust resistant lines also possessed resistance to powdery mildew. It is anticipated that this germplasm will play an important role in developing stripe rust resistant wheat varieties either through direct adoption or using them as parents in breeding programs. [ABSTRACT FROM AUTHOR]

Expressed sequenced tags containing simple sequence repeats (EST-SSRs) were used to identify molecular markers associated with yellow rust resistance in wheat ( Triticum aestivum L.). A cross between yellow rust resistant (PI178383) and susceptible (Harmankaya99) wheat genotypes was performed and respective DNA pools from the resistant and susceptible F seedlings were constructed. 78 EST-SSR primers were used for bulked segregant analysis and one EST-SSR marker ( Pk54), identified as 200 bp fragment, was present in the resistant parent and resistant F hybrids but not in the susceptible ones. 108 wheat genotypes differing in yellow rust resistance were screened with Pk54 and 68 % of the wheat genotypes, known to be yellow rust resistant, had the Pk54 marker, further suggesting that the presence of this marker correlates with yellow rust resistance. [ABSTRACT FROM AUTHOR]

The effect of stripe rust (Puccinia striiformis) on yield and yield components of three common wheat cultivars was studied in 2002 and 2003 in Bale highlands, Ethiopia. The objectives were to quantify amount of loss in yield and yield components incurred by stripe rust on common wheat, and assess the relationship between stripe rust and yield. Different severity levels were created by varying triademefon spray intervals. Stripe rust significantly affected grain yield, kernels per spike (NKPS) and thousand kernels weight (TKW) of the susceptible Wabe cultivar. Losses of 3819 kg ha-1 (71%) grain yield, 21.5 (35%) NKPS and 13.9 g (37%) TKW occurred on Wabe. Each unit increase in stripe rust severity resulted in yield reduction of 41 - 47 kg ha-1 at Agarfa. The study indicated that stripe rust causes intolerable high yield loss in common wheat production and the importance of using resistant cultivars and applying fungicide on susceptible cultivars. [ABSTRACT FROM AUTHOR]

The tendency of unpaired meiotic chromosomes to undergo centric misdivision was exploited to translocate leaf rust and stripe rust resistance genes from an Aegilops kotschyi addition chromosome to a group 2 chromosome of wheat. Monosomic and telosomic analyses showed that the translocation occurred to wheat chromosome arm 2DL. The introgressed region did not pair with the corresponding wheat 2DL telosome during meiosis suggesting that a whole arm may have been transferred. Female transmission of the resistance was about 55% whereas male transmission was strongly preferential (96%). The symbols Lr54 and Yr37 are proposed to designate the new resistance genes. [ABSTRACT FROM AUTHOR]

A hexaploid wheat (Triticum aestivum L.) bacterial artificial chromosome (BAC) library was constructed for cloning Yr5 and other genes conferring resistance to stripe rust (Puccinia striiformis f. sp. tritici). Intact nuclei from a Yr5 near-isogenic line were used to isolate high molecular weight DNA, which was partially cleaved with HindIII and cloned into pECBAC1 and pIndigoBAC-5 vectors. The wheat BAC library consisted of 422 400 clones arrayed in 1100 micro-titer plates (each plate with 384 wells). Random sampling of 300 BAC clones indicated an average insert size of 140 kb, with a size range from 25 to 365 kb. Ninety percent of the clones in the library had an insert size greater than 100 kb and fewer than 5% of the clones did not contain inserts. Based on an estimated genome size of 15 966 Mb for hexaploid wheat, the BAC library was estimated to have a total coverage of 3.58× wheat genome equivalents, giving approximately 96% probability of identifying a clone representing any given wheat DNA sequence. Twelve BAC clones containing an Yr5 locus-specific marker (Yr5STS7/8) were successfully selected by PCR screening of 3-dimensional BAC pools. The results demonstrated that the T. aestivum BAC library is a valuable genomic resource for positional cloning of Yr5. The library also should be useful in cloning other genes for stripe rust resistance and other traits of interest in hexaploid wheat. [ABSTRACT FROM AUTHOR]

Autophagy-related 8 (ATG8) protein has been reported to be involved in plant’s innate immune response, but it is not clear whether such genes play a similar role in cereal crops against obligate biotrophic fungal pathogens. Here, we reported an ATG8 gene from wheat (Triticum aestivum), designated TaATG8j. This gene has three copies located in chromosomes 2AS, 2BS, and 2DS. The transcriptions of all three copies were upregulated in plants of the wheat cultivar Suwon 11, inoculated with an avirulent race (CYR23) of Puccinia striiformis f. sp. tritici (Pst), the causal fungal pathogen of stripe rust. The transient expression of TaATG8j in Nicotiana benthamiana showed that TaATG8j proteins were distributed throughout the cytoplasm, but mainly in the nucleus and plasma membrane. The overexpression of TaATG8j in N. benthamiana slightly delayed the cell death caused by the mouse apoptotic protein BAX (BCL2-associated X protein). However, the expression of TaATG8j in yeast (Schizosaccharomyces pombe) induced cell death. The virus-induced gene silencing of all TaATG8j copies rendered Suwon 11 susceptible to the avirulent Pst race CYR23, accompanied by an increased fungal biomass and a decreased necrotic area per infection site. These results indicate that TaATG8j contributes to wheat resistance against stripe rust fungus by regulating cell death, providing information for the understanding of the mechanisms of wheat resistance to the stripe rust pathogen. [ABSTRACT FROM AUTHOR]

A new gene, Yr24, for resistance to stripe rust was transferred from a durum accession to common wheat via an amphiploid (synthetic wheat) with Aegilops tauschii. Yr24 was located in chromosome 1B by monosomic analysis. Its genetic linkage of 4 cm with Yr15 indicated its localization to the short arm. [ABSTRACT FROM AUTHOR]