Stripe Rust Resistance Research Articles

High-density mapping of durable and broad-spectrum stripe rust resistance gene Yr30 in wheat.

The durable stripe rust resistance gene Yr30 was fine-mapped to a 610-kb region in which five candidate genes were identified by expression analysis and sequence polymorphisms. The emergence of genetically diverse and more aggressive races of Puccinia striiformis f. sp. tritici (Pst) in the past twenty years has resulted in global stripe rust outbreaks and the rapid breakdown of resistance genes. Yr30 is an adult plant resistance (APR) gene with broad-spectrum effectiveness and its durability. Here, we fine-mapped the YR30 locus to a 0.52-cM interval using 1629 individuals derived from residual heterozygous F5:6 plants in a Yaco"S"/Mingxian169 recombinant inbred line population. This interval corresponded to a 610-kb region in the International Wheat Genome Sequencing Consortium (IWGSC) RefSeq version 2.1 on chromosome arm 3BS harboring 30 high-confidence genes. Five genes were identified as candidate genes based on functional annotation, expression analysis by RNA-seq and sequence polymorphisms between cultivars with and without Yr30 based on resequencing. Haplotype analysis of the target region identified six haplotypes (YR30_h1-YR30_h6) in a panel of 1215 wheat accessions based on the 660K feature genotyping array. Lines with YR30_h6 displayed more resistance to stripe rust than the other five haplotypes. Near-isogenic lines (NILs) with Yr30 showed a 32.94% higher grain yield than susceptible counterparts when grown in a stripe rust nursery, whereas there was no difference in grain yield under rust-free conditions. These results lay a foundation for map-based cloning Yr30.

Identification and molecular mapping of resistance genes for adult-plant resistance to stripe rust in spring wheat germplasm line PI660076

Wheat is one of the major food crops worldwide. Stripe rust can cause a great loss of wheat yield, especially when the disease is prevalent. Chemical control not only causes the loss of resistance to stripe rust but also has a serious impact on the human body and environment. Therefore, the most economical measure to control wheat stripe rust is to cultivate resistant varieties. Rapid variation of stripe rust races often leads to rapid "loss" of resistance to stripe rust disease; therefore, breeders and researchers have to continuously explore new stripe rust resistance genes to provide new resistance sources for the rapid variation of stripe rust races. Previous studies have confirmed that PI660076, a spring wheat line, showed stripe rust resistance under natural conditions at the adult stage, which has great value in breeding programs. In this study, a recombinant inbred lines (RIL) population was constructed by crossing the wheat line PI660076 with the stripe rust-susceptible line AvS. Genotyping of the population was performed using a wheat 15 K SNP array. Three QTLs were identified using phenotypic data over four years across three environments. The resistance type of each QTL was determined by inoculating the RIL lines with single and homozygous QTL during the seedling and adult stages under controlled conditions. The all-stage resistance (ASR) QTL, QYr076.jaas-2A (flanked by SNP marker AX-11048464 and Kompetitive Allele-Specific PCR (KASP) marker KASP_4940) explained 7.13–16.58% and 6.95–7.25% of infection type (IT) and disease severity (DS), respectively. The adult-plant resistance (APR) resistance QTL, QYr076.jaas-4D.1 (flanked by KASP marker KASP_0795 and SNP marker AX-111567243,) explained 6.85–12.70% and 7.94–17.26% of IT and DS, respectively. The APR resistance QTL, QYr076.jaas-4D.2 flanked by KASP markers KASP_9130 and KASP_6535, explained 7.97–39.19% and 8.77–20.55% of the phenotypic variation in IT and DS, respectively. All the three QTLs are likely to be new. The obtained results lay a foundation for further utilization of the stripe rust-resistant line PI660076, as well as for fine mapping and molecular marker-assisted selection breeding.Graphical

Characterization of a 4.1 Mb inversion harboring the stripe rust resistance gene YR86 on wheat chromosome 2AL

Wheat cultivar Zhongmai 895 was earlier found to carry YR86 in an 11.6 Mb recombination-suppressed region on chromosome 2AL when crossed with Yangmai 16. To fine-map the YR86 locus, we developed two large F2 populations from crosses Emai 580/Zhongmai 895 and Avocet S/Zhongmai 895. Remarkably, both populations exhibited suppressed recombination in the same 2AL region. Collinearity analysis across Chinese Spring, Aikang 58, and 10+ wheat genomes revealed a 4.1 Mb chromosomal inversion spanning 708.5–712.6 Mb in the Chinese Spring reference genome. Molecular markers were developed in the breakpoint and were used to assess a wheat cultivar panel, revealing that Chinese Spring, Zhongmai 895, and Jimai 22 shared a common sequence named InvCS, whereas Aikang 58, Yangmai 16, Emai 580, and Avocet S shared the sequence named InvAK58. The inverted configuration explained the suppressed recombination observed in all three bi-parental populations. Normal recombination was observed in a Jimai 22/Zhongmai 895 F2 population, facilitating mapping of YR86 to a genetic interval of 0.15 cM corresponding to 710.27–712.56 Mb falling within the inverted region. Thirty-three high-confidence genes were annotated in the interval using the Chinese Spring reference genome, with six identified as potential candidates for YR86 based on genome and transcriptome analyses. These results will accelerate map-based cloning of YR86 and its deployment in wheat breeding.

Identification of a stripe rust resistance gene in Chinese wheat line Shaannong69 using bulked-segregant sequencing

Identification of a stripe rust resistance gene in Chinese wheat line Shaannong69 using bulked-segregant sequencing

Molecular Cytogenetic Characterization of Novel Wheat-Rye T1RS.1AL Translocation Lines with Resistance to Powdery Mildew and Stripe Rust Derived from the Chinese Rye Landrace Qinling.

Stripe rust and powdery mildew are serious diseases that severely decrease the yield of wheat. Planting wheat cultivars with powdery mildew and stripe rust resistance genes is the most effective way to control these two diseases. Introducing disease resistance genes from related species into the wheat genome via chromosome translocation is an important way to improve wheat disease resistance. In this study, nine novel T1RS.1AL translocation lines were developed from the cross of wheat cultivar Chuannong25 (CN25) and a Chinese rye Qinling. The results of non-denaturing fluorescence in situ hybridization and PCR showed that all new lines were homozygous for the T1RS.1AL translocation. These new T1RS.1AL translocation lines exhibited strong resistance to stripe rust and powdery mildew. The cytogenetics results indicated that the resistance of the new lines was conferred by the 1RS chromosome arms, which came from Qinling rye. The genetic analysis indicated that there were new dominant resistance genes on the 1RS chromosome arm resistant to stripe rust and powdery mildew, and their resistance patterns were different from those of Yr9, Pm8, and Pm17 genes. In addition, the T1RS.1AL translocation lines generally exhibited better agronomic traits in the field relative to CN25. These T1RS.1AL translocations have great potential in wheat-breeding programs in the future.

Comparative analysis of stripe rust resistance in seedling stage and Yr gene incidence in spring and winter wheat from Xinjiang, China.

Stripe rust, caused by the fungus Puccinia striiformis f.sp. tritici (Pst), poses a significant threat to global wheat production. This study aims to analyze the distribution of stripe rust resistance genes, characterize resistance phenotypes at the seedling stage of 137 spring and 149 winter wheat varieties in Xinjiang, China, and discern differences in resistance between spring and winter wheat varieties. We used various Pst races (CYR23, CYR29, CYR31, CYR32, CYR33, CYR34) to characterize seedling resistance of spring and winter wheat varieties and to correlate resistance to the presence of wheat resistance genes (Yr5, Yr9, Yr10, Yr15, Yr17, Yr18, Yr26, Yr41, Yr80, Yr81) using molecular markers. Among spring wheat varieties, 62, 60, 42, 26, 51, and 24 varieties exhibited resistance to CYR23, CYR29, CYR31, CYR32, CYR33, and CYR34, respectively, with four varieties resistant to all varieties. Among winter wheat varieties, 66, 32, 69, 26, 83, 40 varieties demonstrated resistance to CYR23, CYR29, CYR31, CYR32, CYR33, and CYR34, respectively, with four varieties resistant to all varieties. Molecular testing revealed that, in spring wheat, 2, 17, 21, 61, 10, 0, 10, 79, and 32 varieties carried Yr9, Yr10, Yr15, Yr17, Yr18, Yr26, Yr41, Yr80, and Yr81 genes, respectively. In winter wheat, 40, 20, 7, 143, 15, 1, 6, 38, and 54 varieties carried Yr9, Yr10, Yr15, Yr17, Yr18, Yr26, Yr41, Yr80, and Yr81 genes, respectively. Notably, winter wheat exhibited a significantly higher resistance frequency than spring wheat, particularly in the incidence of Yr9, Yr10, Yr17, Yr18, and multi-gene combinations. In summary, this study provides information on seedling stage resistance to stripe rust 286 Xinjiang wheat varieties, elucidates the distribution of resistance genes in this population, and offers a mechanistic basis for breeding durable resistance in wheat. varieties from Xinjiang.

Identification of candidate genes for adult plant stripe rust resistance transferred from Aegilops ventricosa 2NvS into wheat via fine mapping and transcriptome analysis.

An adult plant gene for resistance to stripe rust was narrowed down to the proximal one-third of the 2NvS segment translocated from Aegilops ventricosa to wheat chromosome arm 2AS, and based on the gene expression analysis, two candidate genes were identified showing a stronger response at the adult plant stage compared to the seedling stage. The 2NvS translocation from Aegilops ventricosa, known for its resistance to various diseases, has been pivotal in global wheat breeding for more than three decades. Here, we identified an adult plant resistance (APR) gene in the 2NvS segment in wheat line K13-868. Through fine mapping in a segregating near-isogenic line (NIL) derived population of 6389 plants, the candidate region for the APR gene was narrowed down to between 19.36Mb and 33Mb in the Jagger reference genome. Transcriptome analysis in NILs strongly suggested that this APR gene conferred resistance to stripe rust by triggering plant innate immune responses. Based on the gene expression analysis, two disease resistance-associated genes within the candidate region, TraesJAG2A03G00588940 and TraesJAG2A03G00590140, exhibited a stronger response to Puccinia striiformis f. sp. tritici (Pst) infection at the adult plant stage than at the seedling stage, indicating that they could be potential candidates for the resistance gene. Additionally, we developed a co-dominant InDel marker, InDel_31.05, for detecting this APR gene. Applying this marker showed that over one-half of the wheat varieties approved in 2021 and 2022 in Sichuan province, China, carry this gene. Agronomic trait evaluation of NILs indicated that the 2NvS segment effectively mitigated the negative effects of stripe rust on yield without affecting other important agronomic traits. This study provided valuable insights for cloning and breeding through the utilization of the APR gene present in the 2NvS segment.

Fine mapping and characterization of stripe rust resistance gene YrAYH in near-isogenic lines derived from a cross involving wheat landrace Anyuehong

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease in wheat worldwide. Discovering and characterizing new resistance genes/QTL is crucial for wheat breeding programs. In this study, we fine-mapped and characterized a stripe rust resistance gene, YRAYH, on chromosome arm 5BL in the Chinese wheat landrace Anyuehong (AYH). Evaluations of stripe rust response to prevalent Chinese Pst races in near-isogenic lines derived from a cross of Anyuehong and Taichung 29 showed that YrAYH conferred a high level of resistance at all growth stages. Fine mapping using a large segregating population of 9748 plants, narrowed the YRAYH locus to a 3.7 Mb interval on chromosome arm 5BL that included 61 annotated genes. Transcriptome analysis of two NIL pairs identified 64 upregulated differentially expressed genes (DEGs) in the resistant NILs (NILs-R). Annotations indicated that many of these genes have roles in plant disease resistance pathways. Through a combined approach of fine-mapping and transcriptome sequencing, we identified a serine/threonine-protein kinase SRPK as a candidate gene underlying YrAYH. A unique 25 bp insertion was identified in the NILs-R compared to the NILs-S and previously published wheat genomes. An InDel marker was developed and co-segregated with YrAYH. Agronomic trait evaluation of the NILs suggested that YrAYH not only reduces the impact of stripe rust but was also associated with a gene that increases plant height and spike length.

Integrated genome-wide association and transcriptomic analysis to identify receptor kinase genes to stripe rust resistance in wheat germplasm from southwestern China

Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat worldwide. Identification of new and elite Pst-resistance loci or genes has the potential to enhance overall resistance to this pathogen. Here, we conducted an integrated genome-wide association study (GWAS) and transcriptomic analysis to screen for loci associated with resistance to stripe rust in 335 accessions from Yunnan, including 311 landraces and 24 cultivars. Based on the environmental phenotype, we identified 113 protein kinases significantly associated with Pst resistance using mixed linear model (MLM) and generalized linear model (GLM) models. Transcriptomic analysis revealed that 52 of 113 protein kinases identified by GWAS were up and down regulated in response to Pst infection. Among these genes, a total of 15 receptor kinase genes were identified associated with Pst resistance. 11 candidate genes were newly discovered in Yunnan wheat germplasm. Our results revealed that resistance alleles to stripe rust were accumulated in Yunnan wheat germplasm, implying direct or indirect selection for improving stripe rust resistance in elite wheat breeding programs.

Characterization and identification of sources of rust resistance in Triticum militinae derivatives

Triticum militinae (2n = 4X = 28, AtAtGG), belonging to the secondary gene pool of wheat, is known to carry resistance to many diseases. Though some disease resistance genes were reported from T. timopheevii, the closest wild relative of T. militinae, there are no reports from T. militinae. Twenty-one T. militinae Derivatives (TMD lines) developed at the Division of Genetics, IARI, New Delhi, were evaluated for leaf and stripe rusts at seedling and adult plant stages. Eight TMD lines (6–4, 6–5, 11–6, 12–4, 12–8, 12–12, 13–7 and 13–9) showed seedling resistance to both leaf and stripe rusts while six TMD lines (7–5, 7–6, 11–5, 13–1, 13–3 and 13–4) showed seedling resistance to leaf rust but adult plant resistance to stripe rust and three TMD lines (9–1, 9–2 and 15) showed seedling resistance to leaf rust but susceptibility to stripe rust. Three TMD lines (2–7, 2–8 and 6–1) with adult plant resistance to leaf and stripe rusts were found to carry the known gene Lr34/Yr18. Ten TMD lines (7–5, 7–6, 9–1, 9–2, 11–5, 11–6, 12–12, 12–4, 12–8, and 15) with seedling resistance to leaf rust, showing absence of known genes Lr18 and Lr50 with linked markers requires further confirmation by the test of allelism studies. As not a single stripe rust resistance gene has been reported from T. militinae or its close relative T. timpopheevii, all the 8 TMD lines (6–4, 6–5, 11–6,12–4, 12–8, 12–12, 13–7 and 13–9) identified of carrying seedling resistance to stripe rust and 3 TMD lines (13–1, 13–3 and 13–4) identified of carrying adult plant resistance to stripe rust are expected to carry unknown genes. Also, all the TMD lines were found to be cytologically stable and thus can be used in inheritance and mapping studies.

Evaluation of stripe rust resistance and genome-wide association study in wheat varieties derived from the International Center for Agricultural Research in the Dry Areas.

159 wheat varieties obtained from ICARDA, CYR32, CYR33 and CYR34 were used to evaluate the stripe rust resistance in this study. Seedling resistance was carried out in the green house at the two-leaf stage. Adult-plant resistance was carried out between 2022 and 2023 in Xining and Guide, respectively. A total of 24,151 high-quality SNP loci were obtained from a 55K SNP chip data. Genome-wide association study was carried out between SNP loci and stripe rust resistance. Seedling resistance screening revealed that 91.8% (146) of wheat varieties were resistant to CYR32 and CYR33, while only 49.7% (79) of wheat varieties were resistant to CYR34. Adult-plant resistance showed 153 (96.2%) germplasms represented resistance in 2022, while only 85 (53.4%) showed resistance in 2023. An association study using the 55K SNP chip data results combined with disease ratings of 159 materials at both the seedling and adult stages discovered 593 loci related to stripe rust resistance (P ≤ 0.0001). These loci exhibited contribution rates ranging from 11.1% to 18.7%. Among them, 71 were significantly related to resistance against CYR32 at the seedling stage, with a contribution rate of 12.7%-17.2%. Constituting the vast majority, 518 loci distributed across 21 chromosomes were significantly related to CYR33 at the seedling stage, with a contribution rate of 12.6%-18.7%. Fewer loci were found to be associated with disease resistance in adult plants. In E1 environment, a sole locus was detected on chromosome 2B with a contribution rate of 14.4%. In E2 environment, however, exhibited three loci across chromosomes 2B, 4A, and 7B with contribution rates ranging from 11.1% to 16.9%. A total of 68 multi-effect loci were significantly related to resistance against both CYR32 and CYR33 at the seedling stage, and one stable locus was significantly associated with stripe rust resistance at the adult plant stage.

A Combination of Resistance Genes Confers High and Durable Resistance Against Stripe Rust in Wheat Cultivar Lantian 26.

'Lantian 26', a leading elite winter wheat cultivar in Gansu Province since its release in 2010, exhibits high resistance or immunization to stripe rust in the adult-plant stage under a high disease pressure in Longnan (southeastern Gansu). Identifying the resistance genes in 'Lantian 26' could provide a basis for enhanced durability and high levels of resistance in wheat cultivars. Here, a segregating population was developed from a cross between a highly susceptible wheat cultivar Mingxian 169 and the highly stripe rust-resistant 'Lantian 26'. The F2 and F2:3 progenies of the cross were inoculated with multiple prevalent virulent races of stripe rust for adult-plant-stage-resistance evaluation in two different environments. Exon sequence alignment analysis revealed that a stripe rust resistance gene on the 718.4- to 721.2-Mb region of chromosome 7BL, tentatively named as YrLT26, and a cosegregation sequence-tagged site (STS) marker GY17 was developed and validated using the F2:3 population and 103 wheat cultivars. The other two resistance genes, Yr9 and Yr30, were also identified in 'Lantian 26' using molecular markers. Therefore, the key to high and durable resistance to stripe rust at the adult stage is the combination of Yr9, Yr30, and YrLT26 genes in 'Lantian 26'. This could be a considerable strategy for improving the wheat cultivars with effective and durable resistance in the high-pressure region for stripe rust.

Combining Ability Analysis and Genetic Studies of Stripe Rust Resistance in Bread Wheat Genotypes

A set of eighteen F1 and F2 experimental crosses were grown in a randomized complete block design (RCBD) with three replications. From lines, TD-1 was on top by showing greater and significant general combining ability (GCA) effects for maximum number characters including grain yield in both (F1 and F2) populations, while tester Benazir remained exceptional by showing higher and significant specific combining ability (GCA) effects for majority traits including grain yield in F1 and F2 populations, as a result, both parents would contribute significantly to the improvement of the bread wheat. Regarding the SCA effects in F1 population, the hybrids TD-1 × Pakistan-2013, TJ-83 × Benazir, and NIA-Sundar × NIA-Sarang and from F2 populations, the crosses TD-1 × Benazir, TJ-83 × Benazir, Kiran-95 × NIA-Sarang and NIA-Amber × Pakistan-2013 expressed desirable and maximum SCA effects for number of traits including grain yield, thus may be preferred in future wheat breeding programs. Disease reaction on selected 18 F2 populations was performed, the introgression stripe rust resistance showed single dominant gene. The genetic analysis reported the involvement of major genes for stripe rust resistance. These findings could be used to grow high-yielding wheat lines that could have a profitable yield in stripe rust-prone areas.

Genome wide association study and genomic prediction for stripe rust resistance at the seedling stage in advanced spring bread wheat genotypes of ICARDA Morocco

One of the most devastating diseases impacting wheat (Triticum aestivum L.) worldwide is stripe rust, which is propagated by Puccinia striiformis f. Sp. Tritici (Pst). The development and utilization of resistant cultivars offer an effective and eco-friendly approach to manage this disease. However, the emergence of new virulent strains of Pst, driven by continuous mutations within the pathogen, rapidly undermines the effectiveness of existing resistance genes. This necessitates the ongoing identification and incorporation of new resistance genes to breed wheat varieties that can maintain resistance against evolving strains of the pathogen. A genome-wide association study (GWAS) and genomic prediction (GP) were conducted using yellow rust data from the seedling stage under controlled conditions, involving 200 elite bread wheat genotypes and 13,151 SNP markers. GWAS analysis identified fourteen SNP markers significantly associated with yellow rust resistance, using a general linear model (GLM). The markers (wsnp Ex c1085 2078944, wsnp Ku c3682 6,786,230) on chromosome 1D and (wsnp Ex c8240 13,914,674) on chromosome 3A were notably correlated with seedling-level resistance to yellow rust. Additionally, the marker 'AX-94703603′ on chromosome 3A, which recorded the highest -Log10(p) value, was linked to the gene 'TraesCS3A02G335300' encoding the protein kinase domain. These markers, after validation, could be utilized for gene pyramiding in wheat breeding programs to enhance rust resistance through marker-assisted selection.

Identification of synthetic wheat lines with broadly effective stripe rust resistance

Wheat stripe/yellow rust (WYR), caused by Puccinia striiformis f. sp. tritici (Pst), is a major constraint in global wheat production. A set of 766 hexaploid synthetic wheat lines, including primary crosses of Triticum turgidum x Aegilops tauschii and their derivatives, were screened in artificially rust inoculated field nurseries for three seasons. From this set, a core set of 94 non-lodging lines with unique pedigrees and resistance to Pst that was consistent across years was established. The core set was tested for adult plant field response under field conditions for three seasons in Australia and at least one crop season in Ethiopia, India, Kenya, Nepal and Pakistan. It was also challenged with an array of well-defined Pst pathotypes at seedling growth stages in the greenhouse, and genotyped with molecular markers linked to the adult plant resistance (APR) genes Yr18, Yr36 and Yr46. Combined analysis of field rust responses, multi-pathotype seedling phenotyping and marker genotyping resolved seven classes of Pst resistance: uncatalogued (new) APR (UAPR, 11%), uncatalogued seedling resistance (USR, 46%), known seedling resistance (KSR, 5%), KSR + USR (2%), Yr18 + UAPR (4%), Yr18 + USR (29%) and Yr18 + KSR (3%). A majority of the lines carrying UAPR and USR either singly or in combination showed high levels of field resistance across all field sites and years of testing, demonstrating that these lines represent a valuable resource for breeding wheat for resistance to Pst.

Phenotypic and genotypic evaluation of Turkish bread wheat (Triticum aestivum L.) varieties to stripe rust (Puccinia striiformis f.sp. tritici)

AbstractWheat stripe rust, which is caused by the basidiomycetes fungal pathogen Puccinia striiformis f.sp. tritici (Pst), is one of the most destructive diseases of wheat in Türkiye and worldwide. In this study, a total of 99 bread wheat varieties were assessed at the adult plant stage under natural infection conditions during the 2021–2022 and 2022–2023 growing seasons. Additionally, specific molecular markers were used to genotype the stripe rust resistance genes Yr26, Yr32, Yr36, Yr44 and YrSP. Disease severity was determined using the modified Cobb scale and infection reactions of each bread wheat varieties were evaluated, and also coefficient of infection value was calculated based on those parameters. To determine whether the wheat varieties had resistance gene(s), specific molecular markers associated with the resistance genes Yr26, Yr32, Yr36, Yr44 and YrSP were used. In the field trials, the majority of the tested varieties showed moderately susceptible and susceptible reactions in both years. According to the molecular results, they were positive for Yr32 in three varieties, Yr36 in 25 varieties, YrSP in two varieties and none of them had Yr26. Furthermore, some varieties carried combinations of these genes, such as Yr32 + Yr36, Yr32 + Yr44, Yr36 + Yr44, Yr36 + YrSP, Yr32 + Yr36 + Yr44 and Yr32 + Yr36 + Yr44 + YrSP. On the other hand, it was not determined these resistance genes in 16 varieties. In the literature, these resistance genes were first identified in Turkish bread wheat varieties. In addition, these findings are valuable for the development of wheat cultivars with effective and more durable resistance to stripe rust in Türkiye.

Genetic dissection and identification of stripe rust resistance genes in the wheat cultivar Lanhangxuan 121, a cultivar selected from a space mutation population.

The online version contains supplementary material available at 10.1007/s11032-024-01461-0.

Genetic evaluation of hulless barley (Hordeum vulgare) genotypes for morpho-physiological traits and stripe rust resistance

Nowadays, hulless barley (Hordeum vulgare L.) is gaining importance as a raw material for food industry due to its highly nutritive value. Non-availability of high yield and disease resistant varieties has restricted its production in marginal areas over the last two decades. Therefore, an experiment was conducted during 2017–18 and 2018–19 at the Seed and Research Farm of ICAR-Indian Institute of Wheat and Barley Research, Karnal, Haryana to characterized 11 exotic hulless barley genotypes and 4 Indian barley cultivars for morpho-physiological characters and stripe rust resistance. Seedling resistant test for stripe rust was done at Regional Station (ICAR-Indian Institute of Wheat and Barley Research), Flowerdale, Shimla, Himachal Pradesh. Highly significant genotypic differences were found for morpho-physiological traits during analysis of variance. Genotype DWRNB28 showed a good combination of desirable traits, viz. early maturity (118 days), dwarf plant height (64.4 cm) and high 1000-grain weight (55.2 g). Maximum number of tillers per meter (149) was observed in DWRNB17. Genotype DWRNB25 was found resistant to maximum pathotypes (6S0, 7S0, and Q) at the seedling stage. DWRNB23 and DWRNB25 with pooled ACI=0 and ACI=0.04 respectively, were found immune to stripe rust in field conditions. These promising genotypes can be utilized as donor parents for the development of high-yielding and stripe-rust-resistant hulless barley varieties.

Transcriptome analysis in Aegilops tauschii unravels further insights into genetic control of stripe rust resistance.

The Aegilops tauschii resistant accession prevented the pathogen colonization by controlling the sugar flow and triggering the hypersensitive reaction. This study suggested that NBS-LRRs probably induce resistance through bHLH by controlling JA- and SA-dependent pathways. Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst) is one of wheat's most destructive fungal diseases that causes a severe yield reduction worldwide. The most effective and economically-friendly strategy to manage this disease is genetic resistance which can be achieved through deploying new and effective resistance genes. Aegilops tauschii, due to its small genome and co-evolution with Pst, can provide detailed information about underlying resistance mechanisms. Hence, we used RNA-sequencing approach to identify the transcriptome variations of two contrasting resistant and susceptible Ae. tauschii accessions in interaction with Pst and differentially expressed genes (DEGs) for resistance to stripe rust. Gene ontology, pathway analysis, and search for functional domains, transcription regulators, resistance genes, and protein-protein interactions were used to interpret the results. The genes encoding NBS-LRR, CC-NBS-kinase, and phenylalanine ammonia-lyase, basic helix-loop-helix (bHLH)-, basic-leucinezipper (bZIP)-, APETALA2 (AP2)-, auxin response factor (ARF)-, GATA-, and LSD-like transcription factors were up-regulated exclusively in the resistant accession. The key genes involved in response to salicylic acid, amino sugar and nucleotide sugar metabolism, and hypersensitive response contributed to plant defense against stripe rust. The activation of jasmonic acid biosynthesis and starch and sucrose metabolism pathways under Pst infection in the susceptible accession explained the colonization of the host. Overall, this study can fill the gaps in the literature on host-pathogen interaction and enrich the Ae. tauschii transcriptome sequence information. It also suggests candidate genes that could guide future breeding programs attempting to develop rust-resistant cultivars.

Pathogenicity of Puccinia striiformis f. sp. tritici and quantitative traits on bread wheat landraces in Ethiopia

AbstractBread wheat (Triticum aestivum L.) is severely affected by stripe rust caused by Puccinia striiformis Westend. f. sp. tritici (Pst). This study was conducted to investigate pathogenicity of Pst isolates to bread wheat landraces grown in Ethiopia, establish stripe rust yield loss models and estimate variability in bread wheat quantitative traits. A greenhouse pot experiment was setup to assess seedling stage responses of landraces to Pst and a field study was conducted for adult plant stage evaluation. Among dominant isolates of Pst, Kubsa was the most virulent. Apart from the detection of resistance at the seedling stage study, a broad range of adult‐stage resistance was also observed which can confer durable resistance. Among single‐point models, the onset of severe infection at the development of heading stage causes significant yield loss by stripe rust. The integral yield loss model predicted a strong negative linear relationship between agronomic traits and stripe rust. Hierarchical analysis revealed the presence of three distinct clusters of bread wheat landraces, each forming different stripe rust resistance groups. With the exception of the harvest index and the growth stage parameter of days to heading, all agronomic traits were significantly different for the various landraces. This suggests the presence of diverse genetic resources, which might have also led to different responses to the stripe rust in these materials. This work clarifies the many ways in which landraces of bread wheat react to Pst infection, revealing a range of resistance mechanisms that can be used for efficient disease management.