Stripe Rust Research Articles

Stripe rust effector Pst03724 modulates host immunity by inhibiting NAD kinase activation by a calmodulin.

Puccinia striiformis f. sp. tritici (Pst) secretes effector proteins that enter plant cells to manipulate host immune processes. In this report, we present an important Pst effector, Pst03724, whose mRNA expression level increases during Pst infection of wheat (Triticum aestivum). Silencing of Pst03724 reduced the growth and development of Pst. Pst03724 targeted the wheat calmodulin TaCaM3-2B, a positive regulator of wheat immunity. Subsequent investigations revealed that Pst03724 interferes with the TaCaM3-2B-NAD kinase (NADK) TaNADK2 association and thus inhibits the enzyme activity of TaNADK2 activated by TaCaM3-2B. Knocking down TaNADK2 expression by virus-mediated gene silencing significantly increased fungal growth and development, suggesting a decrease in resistance against Pst infection. In conclusion, our findings indicate that Pst effector Pst03724 inhibits the activity of NADK by interfering with the TaCaM3-2B-TaNADK2 association, thereby facilitating Pst infection.

Molecular Mechanisms of the Stripe Rust Interaction with Resistant and Susceptible Wheat Genotypes.

Rust fungi cause significant damage to wheat production worldwide. In order to mitigate disease impact and improve food security via durable resistance, it is important to understand the molecular basis of host-pathogen interactions. Despite a long history of research and high agricultural importance, still little is known about the interactions between the stripe rust fungus and wheat host on the gene expression level. Here, we present analysis of the molecular interactions between a major wheat pathogen-Puccinia striiformis f. sp. tritici (Pst)-in resistant and susceptible host backgrounds. Using plants with durable nonrace-specific resistance along with fully susceptible ones allowed us to show how gene expression patterns shift in compatible versus incompatible interactions. The pathogen showed significantly greater number and fold changes of overexpressed genes on the resistant host than the susceptible host. Stress-related pathways including MAPK, oxidation-reduction, osmotic stress, and stress granule formation were, almost exclusively, upregulated in the resistant host background, suggesting the requirement of the resistance-countermeasure mechanism facilitated by Pst. In contrast, the susceptible host background allowed for broad overrepresentation of the nutrient uptake pathways. This is the first study focused on the stripe rust pathogen-wheat interactions, on the whole transcriptome level, from the pathogen side. It lays a foundation for the better understanding of the resistant/susceptible hosts versus pathogenic fungus interaction in a broader sense.

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.

Virulence Characterization of Puccinia striiformis f. sp. tritici in China Using the Chinese and Yr Single-Gene Differentials.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat. Identifying Pst races is essential for developing resistant cultivars and managing the disease. In this study, 608 isolates collected from China in 2021 were tested with the Chinese set of 19 wheat variety differentials and the set of 18 Yr single-gene differentials. Of the 119 races detected with the Chinese set of differentials, 94 were new. A higher number (149) of races were identified using the Yr single-gene differentials. The frequencies of virulence factors to 17 of the 19 Chinese differential varieties and to 10 of the 18 Yr single-gene differentials were high (>60%). None of the isolates were virulent to the differentials Zhong 4 (Yr genes unknown) and Triticum spelta Album (Yr5) in the Chinese set and the Yr5 and Yr15 lines in the single-gene set of differentials, indicating that these genes or varieties are effective against the Pst population detected in 2021. Using Nei's genetic distance, the 16 provincial Pst populations were clustered into six groups based on the Chinese set and eight groups based on the Yr single-gene set of differentials. In addition, we found that the same races identified using the Chinese differentials could be further differentiated into different races using the Yr single-gene differentials, suggesting a higher differential capability than the Chinese set of differentials. The results provide a scientific basis for monitoring Pst populations and guiding resistance breeding in China.

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.

Characterization of sucrose nonfermenting-1-related protein kinase 2 (SnRK2) gene family in Haynaldia villosa demonstrated SnRK2.9-V enhances drought and salt stress tolerance of common wheat

BackgroundThe sucrose nonfermenting-1-related protein kinase 2 (SnRK2) plays a crucial role in responses to diverse biotic/abiotic stresses. Currently, there are reports on these genes in Haynaldia villosa, a diploid wild relative of wheat.ResultsTo understand the evolution of SnRK2-V family genes and their roles in various stress conditions, we performed genome-wide identification of the SnRK2-V gene family in H. villosa. Ten SnRK2-V genes were identified and characterized for their structures, functions and spatial expressions. Analysis of gene exon/intron structure further revealed the presence of evolutionary paths and replication events of SnRK2-V gene family in the H. villosa. In addition, the features of gene structure, the chromosomal location, subcellular localization of the gene family were investigated and the phylogenetic relationship were determined using computational approaches. Analysis of cis-regulatory elements of SnRK2-V gene members revealed their close correlation with different phytohormone signals. The expression profiling revealed that ten SnRK2-V genes expressed at least one tissue (leave, stem, root, or grain), or in response to at least one of the biotic (stripe rust or powdery mildew) or abiotic (drought or salt) stresses. Moreover, SnRK2.9-V was up-regulated in H. villosa under the drought and salt stress and overexpressing of SnRK2.9-V in wheat enhanced drought and salt tolerances via enhancing the genes expression of antioxidant enzymes, revealing a potential value of SnRK2.9-V in wheat improvement for salt tolerance.ConclusionOur present study provides a basic genome-wide overview of SnRK2-V genes in H. villosa and demonstrates the potential use of SnRK2.9-V in enhancing the drought and salt tolerances in common wheat.

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.

Identification of adult resistant genes to stripe rust in wheat from southwestern China based on GWAS and WGCNA analysis.

In this study, genome-wide association studies combined with transcriptome data analysis were utilized to reveal potential candidate genes for stripe rust resistance in wheat, providing a basis for screening wheat varieties for stripe rust resistance. Wheat stripe rust, which is caused by the wheat stripe rust fungus (Puccinia striiformis f. sp. tritici, Pst) is one of the world's most devastating diseases of wheat. Genetic resistance is the most effective strategy for controlling diseases. Although wheat stripe rust resistance genes have been identified to date, only a few of them confer strong and broad-spectrum resistance. Here, the resistance of 335 wheat germplasm resources (mainly wheat landraces) from southwestern China to wheat stripe rust was evaluated at the adult stage. Combined genome-wide association study (GWAS) and weighted gene co-expression network analysis (WGCNA) based on RNA sequencing from stripe rust resistant accession Y0337 and susceptible accession Y0402, five candidate resistance genes to wheat stripe rust (TraesCS1B02G170200, TraesCS2D02G181000, TraesCS4B02G117200, TraesCS6A02G189300, and TraesCS3A02G122300) were identified. The transcription level analyses showed that these five genes were significantly differentially expressed between resistant and susceptible accessions post inoculation with Pst at different times. These candidate genes could be experimentally transformed to validate and manipulate fungal resistance, which is beneficial for the development of the wheat cultivars resistant to stripe rust.

Dynamics of Puccinia striiformis f. sp. tritici Urediniospores and Its Relationship with Meteorological Factors in Mianyang, China.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the main diseases of wheat worldwide. Mianyang of Sichuan province in Southwest China is one of main regions for winter Pst inoculum production and spring epidemic and provides urediniospores for infecting wheat in the surrounding regions. Understanding the urediniospore dynamics is important to predict and manage stripe rust. In this study, spore trapping coupled with a TaqMan real-time quantitative PCR method was used to monitor airborne Pst urediniospores from December 2019 to December 2022 in Mianyang. Weather conditions (temperature, relative humidity, daily sunshine duration, and precipitation) were collected for the same period. These data were used to study the relationship of airborne urediniospore density with climatic conditions. The results showed that Pst urediniospores were captured all year round, and the annual peak of urediniospore densities occurred in the period from March to April in which the urediniospores accounted for the largest proportion of the annual total urediniospores. The density of urediniospores in the period of March to April was linearly related to the average sunshine duration of 20 days and average temperature of 15 days prior to the final day of a 7-day trapping period. This relationship needs to be tested in other regions where Pst can sporulate during the winter before it can be integrated with Pst infection conditions to predict rust development.

Genotype × environment interactions of organic winter naked barley for agronomic, disease, and grain quality traits

AbstractThe modeling of genotype × environment interactions (GEI) is important to understand how new crops perform in different environments and management systems. Naked barley (Hordeum vulgare L.) is a type of barley where the hull threshes freely from the grain and can be used for multiple end uses, including food, malt, and animal feed. We examined the performance of a winter naked barley trial grown in organic conditions across three regions and 3 years in northern latitude regions of the United States. We recorded yield, test weight, heading date, plant height, threshability, winter survival, barley stripe rust (Puccinia striiformis f. sp. hordei Westend), barley scald (Rhynchosporium commune Zaffarano, McDonald and Linde sp. nov), and spot blotch (Cochliobolus sativus, anamorph Bipolaris sorokiniana (S. Ito & Kurib.). Barley stripe rust, plant height, heading date, preharvest sprouting, and threshability had high heritability and low GEI. Grain yield, test weight, scald, and winter survival had high GEI and were analyzed using the additive main effect and multiplicative interaction (AMMI) model, genotype plus GEI biplot (GGE), and Finlay–Wilkinson (FW) stability analysis. The environmental patterns explained by the AMMI and GGE models indicated that selection for high GEI traits should occur within target environments and across multiple years within the target environments. Environmental groups were separated by Oregon as the first group and Wisconsin and New York as the second group.

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.

Characterization of a Foxtail Mosaic Virus Vector for Rust Fungus Avirulence Gene Expression in Wheat

The wheat fungal pathogens Puccinia graminis f. sp. tritici ( Pgt), P. striiformis f. sp. tritici, and P. triticina, causing stem, stripe, and leaf rust, respectively, pose a threat to global wheat production. Genetic resistance in the form of resistance ( R) genes provides the best protection, but rust fungal populations change frequently by mutating avirulence (AVR) effectors matching specific R genes, thereby defeating resistance. Hence, characterization of AVR effectors is needed to understand the evolution of pathogen populations, provide insights for extending the effectiveness of R genes, and yield tools for the identification and isolation of R genes. Functional characterization of Avr genes in rust fungi is challenging in these biotrophic pathogens that lack a reliable and efficient transformation system. Studies indicate that the recently engineered foxtail mosaic virus (FoMV) shows promise as an expression system in cereals. In this study, we utilized two confirmed AVR effectors from Pgt, AVRSr35 and AVRSr50, to assess the applicability of FoMV for investigating rust fungus Avr genes. We showed that vector FoMV PV101 carrying PgtAvrSr35 induced a hypersensitive response (HR) in wheat having the corresponding Sr35 resistance gene. However, when carrying PgtAvrSr50, no HR or even mild viral symptoms were seen in a wheat line having Sr50, as this particular wheat line was not susceptible to FoMV. Several wheat cultivars did not support FoMV replication. The results here show that FoMV PV101 is effective as an expression vector for studying rust fungi AVR effectors, but its applicability relies on the susceptibility of wheat cultivars to FoMV. [Formula: see text] Copyright © 2024 His Majesty the King in Right of Canada, as represented by the Minister of Agriculture and Agri-Food Canada. This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Quantitative Trait Loci Mapping for Adult-Plant Stripe Rust Resistance in Chinese Wheat Cultivar Weimai 8

Wheat stripe rust, triggered by Puccinia striiformis f. sp. tritici, is among the most widespread and damaging wheat (Triticum L.) diseases. The development of cultivars harboring adult plant resistance (APR) to stripe rust is a better approach to control the disease. The current study aimed to map APR to stripe rust via the QTL mapping of 165 F2–6 recombinant inbred lines (RILs), derivatives of Weimai 8/Zhengzhou 5389. The collection of phenotypic data for the stripe-rust resistance of both parents and all 165 RILs were conducted at Baoding, Hebei Province, during the 2016–2017 cropping seasons, and at Mianyang, Sichuan Province, during the 2017–2018 and 2018–2019 sowing seasons. The RIL populations and parents were also genotyped with 860 pairs of simple-sequence-repeat (SSR) primers to map APR QTLs to stripe-rust resistant. Moreover, a 55K SNP chip was used for small group bulk segregant analysis conducted to locate the genetic map location and concentration of the SNP markers on the wheat genome. Inclusive composite interval mapping (IciMapping 3.2) software identified four QTLs of stripe-rust resistance on chromosomes 1B, 2AS, 2BS, and 7DS, named QYr.wmy-1B, QYr.wmy-2AS, QYr.wmy-2BS, and QYr.wmy-7DS, which significantly explained 11.56–16.64%, 9.35–12.70%, 7.27–9.95%, and 11.49–15.07% of the phenotypic variation, respectively. All these QTLs were found from the resistant parent, Weimai 8. Meanwhile, the QTLs located on chromosomes 1B and 2AS were found close to Yr18 and Yr9, respectively. Furthermore, the results indicated that QYr.wmy-1B is possibly Yr9 and QYr.wmy-2AS is similar to Yr18 or might be a new QTL, whilst QYr.wmy-2BS and QYr.wmy-7DS were found to be different from previously reported stripe-rust-resistance QTLs and are possibly new QTLs. Overall, the QTLs and their closely associated molecular markers detected in this study could be a great source of input for marker-assisted selection to adult plant stripe-rust resistance in wheat-breeding programs.

First Report of Puccinia striiformis F. Sp. Tritici Race ME2018 in Irrigated Wheat Production in Ethiopia

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a devastating disease of wheat in Ethiopia and the globe. The disease was dynamic and quite complex with the host (variety and plant spp), the environment, and with the pathogen genetic nature. The genetic alternation or change of a pathogen could affect the resistant population in the area. New race identification helps preparedness for the needs a rise to reduce the possible losses due to the problem. The race analysis dynamics identified three yellow rust races; namely, PstS11, PstS16 and ME2018 and one other unknown new race were the major in recent years but in the 2012-2016 Psts1 and PSTS2 were the dominant once. The new race ME2018 race mixture was increased the risk of stripe race epidemics in the area because it is Yr10-virulence race. So regular monitoring, for early detection and identification of new races was crucial.

Integrated management of stripe rust (Puccinia striiformis f. sp. tritici) and its impact on the growth and yield of bread wheat (Triticum aestivum) in Ethiopia

Bread wheat is one of the key food grains in Ethiopia. However, its production and productivity are affected by stripe rust. The objective of this study was to investigate and develop integrated management options for stripe rust using varieties and fungicide application frequency in the study area. A field experiment was conducted at Enarj Enawuga district in the Metaya Kebele farmer training center during the 2022 main cropping season. There were sixteen total treatment combinations [four bread wheat varieties (Ogolcho, Lemu, Hidase, and Local as check), and four Tilt 250 EC fungicide application frequencies (nil, 1, 2, and 3 times)]. The design of the experiment was laid out in a randomized complete block design with factorial arrangements within three replications. Both disease and yield-related data were collected and analyzed using SAS 9.4 software. The disease and yield parameters showed a significant (p < 0.01) difference, and all treated plots had higher yield and lower disease severity than untreated plots. On the untreated plots, the final mean stripe rust severity was 18.53%, 22.57%, 36.73%, and 57.63% on Ogolcho, Lemu, Hidase, and local varieties, respectively. The maximum disease control was recorded from Ogolcho variety (61.31%) with a three-time application of Tilt 250EC. Grain yield and thousand kernel weight increment were obtained at 79.72% and 17.37% from Ogolcho, 100% and 23.44% from Lemu, 94.85% and 34.54% from Hidase, and 102.85% and 49.56% from local varieties treated by three times of Tilt 250EC, respectively. A higher yield reduction and AUDPC (114 DAS) were recorded from untreated plots of local (50.70%, 2,031.49% days−1), and Hidase (48.68%, 1,020.6% days−1) varieties, receptively. The 15-day interval application frequency of Propiconazole increased the grain yield of all tested varieties and reduced stripe rust severity. The Ogolcho variety treated three times yielded the maximum net benefit (216,750 Birr/ha) with an accepted marginal rate of return (22,810%). Therefore, based on the results obtained, producers use the Ogolcho variety with three-time application of propiconazole fungicide for optimum wheat production and could be recommended to manage stripe rust in the study area.

Registration of ‘KS Big Bow’ hard white winter wheat

Abstract‘KS Big Bow’ (Reg. no. CV‐1206, PI 701521), a hard white winter wheat (Triticum aestivum L.) cultivar, was developed by the wheat breeding program at the Agricultural Research Center–Hays, Kansas State University, and released by the Kansas Agricultural Experiment Station in 2022. KS Big Bow was selected from a single cross of KS050223M‐2/KS11HW15 using a modified bulk breeding method. The main objective of this cross is to release a competitive hard white winter wheat cultivar with adaptation to the dryland production in western Kansas. KS Big Bow is an F5‐derived line and was tested in yield trials from 2017 to 2022 in Kansas before its release. It has performed well in dryland yield trials in western Kansas. KS Big Bow has a medium to medium‐early maturity and medium plant height. Its test weight and straw strength are good. KS Big Bow has a good disease‐resistant package including resistance to Wheat streak mosaic virus, moderate resistances to stripe rust (caused by Puccinia striiformis Westend. f. sp. tritici Erikss.) and stem rust (caused by P. graminis Pers f. sp. tritici Eriks. &amp; E. Henn.), and intermediate resistance to Barley yellow dwarf virus. Its milling and baking qualities are about average.

Favorable Loci Identified for Stripe Rust Resistance in Chinese Winter Wheat Accessions via Genome-Wide Association Study.

Stripe rust (or yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of wheat worldwide. Currently, the utilization of resistant cultivars is the most viable way to reduce yield losses. In this study, a panel of 188 wheat accessions from China was evaluated for stripe rust resistance, and genome-wide association studies were performed using high-quality Diversity Arrays Technology markers. According to the phenotype and genotype data, a total of 26 significant marker-trait associations were identified, representing 18 quantitative trait loci (QTLs) on chromosomes 1B, 2A, 2B, 3A, 3B, 5A, 5B, 6B, 7B, and 7D. Of the 18 QTLs, almost all were associated with adult plant resistance (APR) except QYr.nwsuaf-6B.2, which was associated with all-stage resistance (also known as seedling resistance). Three of the 18 QTLs were mapped far from previously identified Pst resistance genes and QTLs and were considered potentially new loci. The other 15 QTLs were mapped close to known resistance genes and QTLs. Subsequent haplotype analysis for QYr.nwsuaf-2A and QYr.nwsuaf-7B.3 revealed the degrees of resistance of the panel in the APR stage. In summary, the favorable alleles identified in this study may be useful in breeding for disease resistance to stripe rust.

Mapping of a Recessive Gene for All-Stage Resistance to Stripe Rust in a Wheat Line Derived from Cultivated Einkorn (Triticum monococcum).

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive fungal diseases of wheat. Cultivated einkorn (Triticum monococcum L. ssp. monococcum, 2n = 2x = 14, AmAm), one of the founder crops of agriculture, harbors unexploited genetic sources for wheat improvement. An advanced wheat line, Z15-1949, with 42 chromosomes, selected from the hybrids of Pst-susceptible common wheat cultivar Crocus and resistant T. monococcum accession 10-1, exhibits high resistance to a mixture of the prevalent Chinese Pst races. Genetic analysis on F1, F2, and F2:3 generations of the cross between Z15-1949 and Pst-susceptible common wheat SY95-71 indicated that the resistance of Z15-1949 was conferred by a recessive gene, tentatively designated as YrZ15-1949. This gene was mapped to the short arm of chromosome 7D using the Wheat 55K single nucleotide polymorphism array, flanked by markers KASP-1949-2 and KASP-1949-10 within a 3.3-cM genetic interval corresponding to a 1.12-Mb physical region in the Chinese Spring reference genome V2.0. The gene differs from previously reported Yr genes on 7D based on their physical positions and is probably a novel gene. YrZ15-1949 would be a valuable resource for developing Pst-resistant wheat cultivars, and the linked markers could be used for marker-assisted selection.

Recognition of wheat rusts in a field environment based on improved DenseNet

Currently, the main methods for detecting plant diseases are sampling and manual visual inspection. However, these methods are time-consuming, laborious and prone to misinterpretation. Rapid advances in Deep Learning (DL) techniques offer new possibilities. This study focused on analysing the confounding factors among three types of wheat rust (stripe rust, leaf rust and stem rust) and aimed to achieve higher classification accuracy. The following approaches were used: (1) Images were collected from several crops and diseases: Wheat Rusts Dataset (WRD), Wheat Common Disease Dataset (WDD), and Common Poaceae Disease Dataset (PDD); (2) Seven common convolutional neural network (CNN) models were made and their performance compared. DenseNet121 was selected as the base model, and its classification results further analysed. The results of the above analyses were then considered using phenotypic morphology and model structure analysis, as well as potential confounder discussions; (3) Adjustments and optimisations were made based on the identified confounding factors. The final improved model, designated Imp-DenseNet, achieved the following accuracies with different datasets: Top-1 accuracy = 98.32% (WRD), Top-3 accuracy = 97.30% (WDD) and Top-5 accuracy = 96.60% (PDD) (Top-x Accuracy refers to the accuracy of the top-ranked category that matches or containing the actual results). The study revealed the potential factors contributing to the confusion among the three wheat rusts and successfully achieved higher accuracy. It can provide a new perspective for future research on other diseases of wheat or other crops.