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BACKGROUND: Wheat powdery mildew, caused by the biotrophic pathogen Blumeria graminis f. sp. tritici (Bgt) is a serious fungal disease. Natural metabolites produced by microorganisms are beneficial biological control agents to inhibit Bgt. In the present study, we investigated the effects of Aspergillus chevalieri BYST01 on wheat powdery mildew. RESULTS: A strain isolated from the termite was identified as A. chevalieri BYST01 by morphological characteristics and phylogenetic analysis. The fermentation broth of BYST01 showed good biocontrol effect on the Bgt in vivo with the control efficiencies of 81.59% and 71.34% under the protective and therapeutic tests, respectively. Four known metabolites, including the main compound physcion (30 mg/L), were isolated from the fermentation broth of BYST01 extracted with ethyl acetate. Importantly, under a concentration of 0.1 mM, physcion repressed conidial germination of Bgt with an inhibition rate of 77.04% in vitro and showed important control efficiencies of 80.36% and 74.64% in vivo under the protective and therapeutic tests, respectively. Hence, the BYST01 showed important potential as a microbial cell factory for the high yield of the green natural fungicide physcion. Finally, the biosynthetic gene clusters responsible for physicon production in BYST01 was predicted by analyzing a chromosome‐scale genome obtained using a combination of Illumina, PacBio, and Hi‐C sequencing technologies. CONCLUSION: Aspergillus chevalieri BYST01 and its main metabolite physcion had a significant control effect on wheat powdery mildew. The biosynthesis pathway of physcion in BYST01 was predicted. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The obligate biotrophic fungal pathogen Blumeria graminis forma specialis tritici (B.g. tritici) is the causal agent of wheat powdery mildew disease. The TOPLESS-related 1 (TPR1) corepressor regulates plant immunity, but its role in regulating wheat resistance against powdery mildew remains to be disclosed. Herein, TaTPR1 was identified as a positive regulator of wheat post-penetration resistance against powdery mildew disease. The transient overexpression of TaTPR1.1 or TaTPR1.2 confers wheat post-penetration resistance powdery mildew, while the silencing of TaTPR1.1 and TaTPR1.2 results in an enhanced wheat susceptibility to B.g. tritici. Furthermore, Defense no Death 1 (TaDND1) and Defense no Death 2 (TaDND2) were identified as wheat susceptibility (S) genes facilitating a B.g. tritici infection. The overexpression of TaDND1 and TaDND2 leads to an enhanced wheat susceptibility to B.g. tritici, while the silencing of wheat TaDND1 and TaDND2 leads to a compromised susceptibility to powdery mildew. In addition, we demonstrated that the expression of TaDND1 and TaDND2 is negatively regulated by the wheat transcriptional corepressor TaTPR1. Collectively, these results implicate that TaTPR1 positively regulates wheat post-penetration resistance against powdery mildew probably via suppressing the S genes TaDND1 and TaDND2. [ABSTRACT FROM AUTHOR]

Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is a destructive wheat disease. Although it can be easily overcome by deployment of resistance genes, the resistance is often quickly compromised by pathogen virulence. Thus, exploration and characterization of new resistance genes is always ongoing. Line NJ3946 derived from a cross of einkorn wheat accessions TA2032 and M389 showed resistance to powdery mildew. Inheritance analysis of an F2 population derived from a cross of NJ3946 and M389 suggested that the resistance was conferred by a dominant allele. With polymorphic markers identified through bulked segregant analysis (BSA), this gene was mapped to a novel locus on chromosome 3A, and was designated as PmNJ3946. Bulked segregant RNA-seq analysis (BSR-seq) was conducted to obtain more closely linked markers, which allowed delimitation of the PMNJ3946 locus to a 0.9 cM interval covering a physical distance of less than 1 Mb. PMNJ3946 was flanked by Xwgrc5153 and SNP-derived marker CHS21_3A008915069, and co-segregated with SNP-derived markers CHS21_3A008939814 and CHS21_3A008943175. The PmNJ3946 discovery expands the diversity of powdery mildew resistance genes and is useful for wheat breeding. [ABSTRACT FROM AUTHOR]

An innovative method, the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene editing system, has significantly revolutionized agriculture by improving the quality of crops and sustaining the environment. CRISPR technology is based on the natural defense mechanism that bacteria and archaea have adapted against invading viruses or other foreign DNA. A genome engineering tool employs a similar mechanism for exceptional crop breeding progression due to its precise gene editing accuracy. This study outlines the present application of CRISPR/Cas9 technology to assess agricultural crop yield, quality, and texture modulation, palatability, nutritional components, disease resistance, and environmental stress. In plants, CRISPR/Cas9 geneediting includes the selection of specific target sites, single guide (sgRNA) design and synthesis, ribonucleoprotein (RNP) or transformation carrier delivery in plant cells, and gene-edited plant transformation and regeneration. The knockout of three mlo genes in wheat confers wheat resistance to powdery mildew disease. The CRISPR/Cas9 system knockout gene Clpsk1, which encodes phytosulfokine, indicates that watermelon with enhanced Fusarium wilt disease resistance can regulate plant immunity. The geneppa6 knockout has improved rice's ability to withstand alkaline stress. Furthermore, the simultaneous editing of multiple genes has contributed to pathway-level plant biotechnology research that widely expands the genome engineering of agronomic traits and its adoptability. All the CRISPR/Cas systems require a specific PAM sequence, which guides the editing sites with specificity. Consequently, developing a PAM-independent CRISPR/Cas system, exploring new relationship between Cas proteins and the modification of Cas enzymes for expanding PAM variants will boost the application of CRISPR/Cas in applied research on agriculture, precision breeding, and ensuring food security. [ABSTRACT FROM AUTHOR]

Rye (Secale cereale) is a valuable gene donor for wheat improvement, especially for its resistance to diseases. Developing rye-derived resistance sources is important for wheat breeding. In the present study, two wheat-rye derivatives, designated JS016 and JS110, were produced by crossing common wheat cultivar Yangmai 23 with Pakistani rye accession W2A. Using sequential genomic in situ hybridization (GISH) and multicolor fluorescence in situ hybridization (mc-FISH), JS016 and JS110 were identified as a T6BS.6RL translocation line and a T6BS.6BL6RL translocation line, respectively. Ten newly 6RL chromosome arm-specific markers were developed and used to confirm the 6RL translocation. The wheat 55K single-nucleotide polymorphism (SNP) array further verified the molecular cytogenetic identification results above and clarified their breakpoints at 430.9 and 523.0 Mb of chromosome 6B in JS016 and JS110, respectively. Resistance spectrum and allelism test demonstrated that JS016 and JS110 possessed novel powdery mildew resistance gene(s) that was derived from the 6RL translocation but differed from Pm20. Moreover, JS016 and JS110 had better agronomic traits than the previously reported 6RL translocation line carrying Pm20. To efficiently transfer and detect the 6RL translocation from JS016 and JS110, one 6RL-specific Kompetitive allele specific PCR (KASP) marker was developed and validated in high throughput marker-assisted selection (MAS). [ABSTRACT FROM AUTHOR]

Genetic transformation is widely used to improve target traits and to study gene function in wheat. However, transformation efficiency depends on the physiological status of the recipient genotype and that is affected by several factors including powdery mildew (PM) infection. The widely used recipient variety Fielder is very susceptible to PM. Therefore, it would be beneficial to develop PM resistant derivatives with high regeneration ability for use in genetic transformation. In the present study PM resistant lines CB037 and Pm97033 carrying genes Pm21 and PmV, respectively, were backcrossed to Fielder with selection for PM resistance. Five lines, NT89, NT90, NT154, and WT48 with Pm21 and line FL347 with PmV were developed, identified by molecular markers and genomic in situ hybridization (GISH) or fluorescent in situ hybridization (FISH), and further subjected to detailed assessment of agronomic traits and regeneration ability following genetic transformation capacity. Lines FL347, WT48, NT89 and NT154 assessed as being equal to, or superior, to Fielder in regeneration and transformation ability are recommended as suitable materials for the replacement of Fielder for wheat gene transfer and genome editing study. [ABSTRACT FROM AUTHOR]

• The ability of two spectra to detect wheat powdery mildew (WPM) was compared. • The performance of multi-feature detection WPM was compared. • A three-band texture index could detect WPM in advance compared to other features. • WPM severity was better estimated using spectral, textural and canopy temperature. Remote sensing based on unmanned aerial vehicle (UAV) is a non-destructive way for wheat powdery mildew (WPM) detection in the field management and crop protection. However, WPM causes complex symptoms and impacts on wheat plants, such as reducing pigment, losing biomass and hindering normal growth. There are great challenges on UAV-based estimation on the disease index (DI) of WPM stress with such kinds of different symptoms during the infected status. Thus, this study aimed to explore the potential multi-features in the UAV-based optical and thermal infrared information to indicate the WPM impact and estimate DI. UAV multispectral and thermal imagery data were acquired continuously in the field during the early, middle, and late infection stages after artificially inoculated with fungal pathogens at the Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Xinxiang, China in 2022. The multi-features between healthy and infected plots were analyzed, mainly including (i) spectral reflectance calculated by mean (labeled as CS) and percentile methods (labeled as LS) from all pixels; (ii) vegetation indices (VIs) constructed from CS and LS; (iii) three-band texture combination indices (TTCI); and (iv) canopy temperature (CT). The optimal variables for DI estimation were determined by the Pearson correlation analysis and a recursive feature elimination algorithm. Multiple linear regression was used to construct DI estimation models based on single and fused types features. Results showed spectral features calculated by LS were more suitable for detecting WPM impacts than CS because more marked differences were observed. Only normalized difference red edge index, plant senescence reflectance index, and Meris terrestrial chlorophyll index could consistently capture changes induced by the disease in the middle to late stages. The proposed TTCI were able to distinguish infection changes compared to spectral and CT features as early as 9–30 days. The combination of spectral features calculated by LS, TTCI2, and CT provided the highest estimation accuracy of DI, with 0.90 of coefficient of determination (R2) and 8.28 % of root mean square error (RMSE). Compared with CS, LS, TTCI2, LS + TTCI2, the R2 was increased by 36 %, 27 %, 7 %, and 3 %, and the RMSE was decrease by 44 %, 39 %, 18 %, and 10 %, respectively. This study analyzed the ability of optical and thermal infrared information to detect the WPM impact and compared the potential of features in estimating DI, which provided a UAV-based remote sensing method for disease prevention and control in the field. [ABSTRACT FROM AUTHOR]

Powdery mildew of wheat is a destructive disease seriously threatening yield and quality worldwide. Comprehensive dissection of new resistance-related loci/genes is necessary to control this disease. LS5082 is a Chinese wheat breeding line with resistance to powdery mildew. Genetic analysis, using the populations of LS5082 and three susceptible parents (Shannong 29, Shimai 22 and Huixianhong), indicated that a single dominant gene, tentatively designated PmLS5082, conferred seedling resistance to different Blumeria graminis f. sp. tritici (Bgt) isolates. Bulked segregant RNA-Seq was carried out to map PmLS5082 and to profile differentially expressed genes associated with PmLS5082. PmLS5082 was mapped to a 0.7 cM genetic interval on chromosome arm 2BL, which was aligned to a 0.7 Mb physical interval of 710.3-711.0 Mb. PmLS5082 differs from the known powdery mildew (Pm) resistance genes on chromosome arm 2BL based on their origin, chromosome positions and/or resistance spectrum, suggesting PmLS5082 is most likely a new Pm gene/allele. Through clusters of orthologous groups and kyoto encyclopedia of genes and genomes analyses, differentially expressed genes (DEGs) associated with PmLS5082 were profiled. Six DEGs in the PmLS5082 interval were confirmed to be associated with PmLS5082 via qPCR analysis, using an additional set of wheat samples and time-course analysis postinoculation with Bgt isolate E09. Ten closely linked markers, including two kompetitive allele-specific PCR markers, were confirmed to be suitable for marker-assisted selection of PmLS5082 in different genetic backgrounds, thus can be used to detect PmLS5082 and pyramid it with other genes in breeding programs. [ABSTRACT FROM AUTHOR]

The fungus Blumeria graminis f. sp. tritici causes wheat powdery mildew disease. Here, we study its spread and evolution by analyzing a global sample of 172 mildew genomes. Our analyses show that B.g. tritici emerged in the Fertile Crescent during wheat domestication. After it spread throughout Eurasia, colonization brought it to America, where it hybridized with unknown grass mildew species. Recent trade brought USA strains to Japan, and European strains to China. In both places, they hybridized with local ancestral strains. Thus, although mildew spreads by wind regionally, our results indicate that humans drove its global spread throughout history and that mildew rapidly evolved through hybridization. The fungus Blumeria graminis f. sp. tritici causes wheat powdery mildew disease. Here, Sotiropoulos et al. analyze a global sample of 172 mildew genomes, providing evidence that humans drove global spread of the pathogen throughout history and that mildew rapidly evolved through hybridization with local fungal strains. [ABSTRACT FROM AUTHOR]

SUMMARY: Cultivated wheat is continually exposed to various pathogens. Blumeria graminis f. sp. tritici (Bgt) causes powdery mildew disease and significant yield loss. Pm60 was cloned from Triticum urartu and confers race‐specific powdery mildew resistance in wheat. Pm60a and Pm60b are allelic variants of Pm60 and have two leucine‐rich repeat motifs deletions and insertions, respectively, which were detected in other T. urartu accessions. Through map‐based cloning, virus‐induced gene silencing, and stable transformation assays, we demonstrated that Pm60a and Pm60b conferred Bgt E09 resistance resembling that provided by Pm60. However, the homozygous Pm60a (but not Pm60 or Pm60b) transformants driven by the native promoters lacked race‐specific resistance when they were inoculated with Bgt E18. As all three T. urartu accessions contained the three foregoing alleles, they had high resistance to Bgt E18. Pyramiding Pm60a with either of the allelic genes in F1 plants did not cause mutual allele suppression or interference with Bgt E18 resistance. Deletion (but not insertion) of the two leucine‐rich repeat motifs in Pm60a substantially narrowed the resistance spectrum. In T. urartu accession PI428210, we identified another locus adjacent to Pm60a and resistant to Bgt E18. Characterization of the alleles at the Pm60 locus revealed their diversity and similarity and may facilitate wheat breeding for resistance to powdery mildew disease caused by B. graminis f. sp. tritici. Significance Statement: In the present study, we identified Pm60a and Pm60b, which are allelic variants at the Pm60 locus. The three foregoing alleles confer resistance to Bgt E09, which causes powdery mildew disease in wheat. Bgt E18 resistance was only absent in Pm60a transgenic plants as this allele has two leucine‐rich repeat (LRR) motif deletions. Pyramiding Pm60a with Pm60 or Pm60b did not hinder Bgt E18 resistance in wheat. Assays involving 54 Bgt isolates confirmed that deletion of the two LRR motifs in Pm60a markedly narrows the Bgt resistance spectrum. In contrast, the insertion of additional LRR motifs in Pm60b did not enhance Bgt resistance. The foregoing findings demonstrated diversity and similarity among alleles at the Pm60 locus and may support wheat breeding for powdery mildew disease resistance. [ABSTRACT FROM AUTHOR]

Simplicillium spp. are mycoparasites that exert growth-inhibitory effects on phytopathogenic fungi. However, limited studies have examined the effects of Simplicillium spp. on powdery mildews. In this study, morphological and molecular analyses revealed that S. aogashimaense is a mycoparasite of the wheat powdery mildew fungus, Blumeria graminis f. sp. tritici (Bgt), under field conditions. The inoculation of Bgt colonies with S. aogashimaense significantly impaired Bgt colony formation and conidial distribution and markedly decreased the biomass of Bgt. To examine the interaction between Simplicillium and Bgt, an S. aogashimaense strain that constitutively expresses green fluorescent protein (GFP) was constructed using the Agrobacterium tumefaciens-mediated transformation (ATMT) method. The hyphae of GFP-expressing S. aogashimaense directly penetrated the B. graminis structures. These findings indicate that ATMT can be employed to reveal the biocontrol activities of physiologically and phylogenetically diverse Simplicillium spp. In vitro, S. aogashimaense exudates compromised Bgt conidial germination and appressorial formation. Thus, S. aogashimaense functions as a potential biological control agent by impeding the development of Bgt and can be a viable alternative for controlling the wheat powdery mildew. To gain further insights into the mechanism underlying this mycoparasitism, the genome of S. aogashimaense was sequenced and assembled. S. aogashimaense harbored seven chromosomes comprising 8963 protein-coding genes. Additionally, two putative effector-coding genes (Sao008714 and Sao006491) were identified. The expression levels of Sao008714 and Sao006491 in S. aogashimaense were dramatically upregulated during the mycoparasitic interaction. In addition, 41 gene clusters putatively involved in the production of secondary metabolites, which exhibit insecticidal, antifungal and antibacterial activities, were identified using genome-wide identification, annotation and analysis of secondary metabolite biosynthesis gene clusters. These results suggest that S. aogashimaense parasitizes Bgt and hence, can be considered for phytopathogen management. [ABSTRACT FROM AUTHOR]

Powdery mildew has a negative impact on wheat growth and restricts yield formation. Therefore, accurate monitoring of the disease is of great significance for the prevention and control of powdery mildew to protect world food security. The canopy spectral reflectance was obtained using a ground feature hyperspectrometer during the flowering and filling periods of wheat, and then the Savitzky–Golay method was used to smooth the measured spectral data, and as original reflectivity (OR). Firstly, the OR was spectrally transformed using the mean centralization (MC), multivariate scattering correction (MSC), and standard normal variate transform (SNV) methods. Secondly, the feature bands of above four transformed spectral data were extracted through a combination of the Competitive Adaptive Reweighted Sampling (CARS) and Successive Projections Algorithm (SPA) algorithms. Finally, partial least square regression (PLSR), support vector regression (SVR), and random forest regression (RFR) were used to construct an optimal monitoring model for wheat powdery mildew disease index (mean disease index, mDI). The results showed that after Pearson correlation, two-band optimization combinations and machine learning method modeling comparisons, the comprehensive performance of the MC spectrum data was the best, and it was a better method for pretreating disease spectrum data. The transformed spectral data combined with the CARS–SPA algorithm was able to extract the characteristic bands more effectively. The number of bands screened was more than the number of bands extracted by the OR data, and the band positions were more evenly distributed. In comparison of different machine learning modeling methods, the RFR model performed the best (coefficient of determination, R 2 = 0.741–0.852), while the SVR and PLSR models performed similarly (R 2 = 0.733–0.836). Taken together, the estimation accuracy of spectral data transformation using the MC method combined with the RFR model (MC-RFR) was the highest, the model R 2 was 0.849–0.852, and the root mean square error (RMSE) and the mean absolute error (MAE) ranged from 2.084 to 2.177 and 1.684 to 1.777, respectively. Compared with the OR combined with the RFR model (OR-RFR), the R 2 increased by 14.39%, and the R 2 of RMSE and MAE decreased by 23.9 and 27.87%. Also, the monitoring accuracy of flowering stage is better than that of grain filling stage, which is due to the relative stability of canopy structure in flowering stage. It can be seen that without changing the shape of the spectral curve, and that the use of MC to preprocess spectral data, the use of CARS and SPA algorithms to extract characteristic bands, and the use of RFR modeling methods to enhance the synergy between multiple variables, and the established model (MC-CARS-SPA-RFR) can better extract the covariant relationship between the canopy spectrum and the disease, thereby improving the monitoring accuracy of wheat powdery mildew. The research results of this study provide ideas and methods for realizing high-precision remote sensing monitoring of crop disease status. [ABSTRACT FROM AUTHOR]

Powdery mildew disease is one of the most deleterious diseases affect wheat reflecting in serious grain yield losses. Control of such disease is important in view of the wheat is the main crop for population consumption in Egypt. Therefore, this study was conducted during 2019-20 at Kafr-El-Dawar region, El-Behira governorate, Egypt to evaluate the suppressing effect of some organic acids applied as foliar spray against disease severity of wheat powdery mildew caused by Blumeria graminis f. sp. tritici under field conditions. Field experiments performed with cultivation of three wheat cultivars at two different fields on two successive sowing dates. During the growing season, wheat plants were sprayed with salicylic, oxalic, benzoic, humic and malic organic acids and the fungicide Topsin M70 twice with one-month interval started at one month after seedlings emergence. No disease symptoms were observed for all cultivars which sown early. The wheat cultivar Giza 171 showed the lowest disease severity (6.2 - 7.8%) followed by Misr 1 (7.5 - 11.5%) and Gemmiza 12 (20.0 - 30.8%) at all applied treatments. High suppressing effect on the severity of powdery mildew was recorded at wheat plants sprayed with salicylic acid (7.8, 7.5 and 21.7%) followed by humic (6.2, 8.3 and 24.2%) and malic acids (6.7, 8.3 and 20.0%) compared with oxalic acid (7.0, 11.5 and 30.8%) and finally the fungicide Topsin M70 (16.3, 23.3 and 27.0%), respectively. An opposite trend for the increase in produced grains yield in parallel with reduction in disease severity was observed. The present results demonstrated that early sown date, suitable resistant varieties in addition to utilize plant resistance inducers are important factors for escaping from disease infection and subsequently its development. [ABSTRACT FROM AUTHOR]

The pathogenesis of wheat powdery mildew (WPM) is from the bottom to upper layers of the plant, and the vertical observation angle limits the early monitoring of WPM status. Multiangle remote sensing could effectively extract spatial structural information from different plant layers. The objectives of this study were to improve the monitoring accuracy of WPM severity and to screen suitable observation angles by developing a novel vegetation index. The monitoring capacities of the novel parameters [Normalized Powdery Mildew Index (NPMI) and Ratio Powdery Mildew Index (RPMI)] and 14 optimized traditional spectral parameters were compared at 13 observation angles and different angle ranges. The correlation between all spectral parameters and disease severity was superior in the forward observation direction than in the backward observation direction in the principal plane of the Sun, and the correlation between the two observation directions decreased with an increase in observation angle. The new spectral parameter suitable for inversion of disease index was RPMI (${R}_{744}/{R}_{762}-0.5 \times R_{710}$), and the best optimal observation angle was +10°, with a 0.852 coefficient, which was 31.74% higher than that of the two-band spectral parameter, ${R}_{744}/{R}_{762}$. The fitting accuracy of the new parameter in the range of 0° to +30° in the forward direction was 0.704. RPMI could not only improve the monitoring accuracy of powdery mildew severity at a single angle but also achieve a more stable monitoring accuracy in the 0° to +30° range in the forward direction, which significantly expands the application scope of remote sensing monitoring and enhances the flexibility of the technology in actual production environments. [ABSTRACT FROM AUTHOR]

Disease resistance (R) gene, RPP13, plays an important role in the resistance of plants to pathogen infections; its function in resistance of wheat to powdery mildew remains unknown. In this study, a RNA‐Seq technique was used to monitor expression of genes in susceptible wheat 'Jing411' and resistant near‐isogenic line 'BJ‐1' in response to powdery mildew infection. Overall, 413 differential expression genes were observed and identified as involved in disease resistance. RPP13 homologous gene on wheat chromosome 7D was preliminarily identified using the wheat 660K SNP chip. RPP13 was highly expressed in 'BJ‐1' and encodes 1,027 amino acids, including CC, NB and LRR domain, termed TaRPP13‐3. After inoculation with powdery mildew, expression of TaRPP13‐3 in resistant wheat changed with time, but average expression was higher when compared to susceptible variety, thus indicating that TaRPP13‐3 is involved in resistance to powdery mildew. Virus‐induced gene silencing (VIGS) was used to inhibit expression of TaRPP13‐3 in resistant parent 'Brock'. Results indicated that silencing of TaRPP13‐3 led to decreased disease resistance in 'Brock'. Overall results of this study indicate that TaRPP13‐3 gene is involved in the defence response of wheat to powdery mildew and plays a positive role in wheat powdery mildew interactions. [ABSTRACT FROM AUTHOR]

Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is an important disease in China. In this study, airborne spore concentrations were monitored using spore samplers and real-time PCR during 2013– 2015 at three locations in Gangu, Gansu province of China. The effects of meteorological variables on spore concentration were analyzed and models were developed for forecasting dynamics of airborne conidia and disease progress. The temperature, solar radiation and rainfall were positively correlated to spore concentrations and disease development. Although there was a negative correlation between relative humidity and spore concentration, relative humidity was positively related with disease development. Stepwise regression models were obtained for predicting the dynamics of airborne conidia based on the positive degree days and accumulation of rainfall (R2 = 0.31, P < 0.01), the positive degree days (R2 = 0.16, P = 0.04) and mean temperatures (R2 = 0.24, P = 0.01) at three locations, respectively. Disease forecasting models were developed based on various meteorological variables and spore concentration, the most important variables being temperature and spore concentration. This knowledge can improve the disease forecasting of wheat powdery mildew in Gangu and help develop better disease control strategies. [ABSTRACT FROM AUTHOR]

Powdery mildew, caused by Blumeria graminis f. sp. tritici, is an important disease of bread wheat (Triticum aestivum L.) in many countries worldwide, including Egypt. Powdery mildew infects all parts of wheat plants that negatively affect grain yield and therefore caused economic loss. Some microorganisms i.e. Bacillus subtilis, B. chitinospora, B. pumilus and yeast (Rhodotarula sp.) were used in the current study as biocontrol agents (BCAs) for controlling powdery mildew in wheat variety (Sakha93), under field conditions, compared to the recommended synthetic fungicide; Tilt. The superior and best treatments decreasing infection type (IT), disease severity (%), and increasing 1000 kernel weight and grain yield per plot. Application of B. subtilis and B. chitinospora, were compared to the other treatments and the tested fungicide. Scanning electron microscopy studies confirmed the superiority of the aforementioned two biocontrol agents (BCAs), as application of each, minimized suppressed mycelial growth and collapsed the spores of the causal pathogen. Application of B. chitinosporain, particular, suppressed the conidial germination, caused a rupture, and deformation of germ tube. Also, both mycelia and conidiospores became shrinking on the surface of the treated wheat leaves. Extracts of the four microorganisms used in this study interacted directly with Blumeria graminis, and this antifungal effect was responsible for the observed disease protection. The obtained results in this investigation gave an evidence to the possible use of such microorganisms as safe and effective alternatives for controlling powdery mildew disease of wheat under field conditions. [ABSTRACT FROM AUTHOR]

BACKGROUND Unmanned aerial vehicles (UAVs) are a recently developed aerial spraying technology. However, the effect of spray volume variation on deposition and pesticide control efficacy is unknown. The effect of three UAV spray volumes (9.0, 16.8 and 28.1 L ha−1) using three different nozzle sizes on droplet deposition and wheat aphid and powdery mildew control efficacy was assessed. An electric air‐pressure knapsack (EAP) sprayer was used as a comparison. RESULTS: Different spray volumes significantly influenced the deposition and control efficacy of the UAV and EAP. For the UAV, a low spray volume of 9.0 L ha−1 with a fine nozzle (nozzle LU120‐01) resulted in lower deposition and control efficacy. Optimal control efficacy was achieved with coarser nozzles (nozzles LU120‐02, ‐03) at > 16.8 L ha−1 volume with systemic insecticide, and at 28.1 L ha−1 with contact insecticide and fungicide. For EAP, a high spray volume led to run‐off, and a spray volume of 225 L ha−1 achieved better deposition and control efficacy. CONCLUSION: The UAV had comparable deposition and efficacy control to the EAP at a higher spray volume (> 16.8 L ha−1) with coarse nozzles, but exhibited inferior deposition and efficacy control at a lower spray volume (<9.0 L ha−1) with fine nozzles. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Powdery mildew caused by Blumeria graminis f.sp. tritici (Bgt) seriously threatens the production of common wheat (Triticum aestivum). In eukaryotes, WD40-repeat (WDR) proteins usually participate in assembling protein complexes involved in a wide range of cellular processes, including defense responses. However, the potential function of WDR proteins in regulating crop resistance to biotrophic fungal pathogens, such as Bgt, remains unclear. In this study, we isolated TaHOS15, encoding a WDR protein, from the Bgt -susceptible wheat cultivar Jing411 and demonstrated that knockdown of TaHOS15 expression using virus- or transient-induced gene-silencing attenuated wheat susceptibility to Bgt. Biochemical and molecular-biological assays revealed that TaHOS15 interacts with TaHDA6, a wheat homolog of Arabidopsis histone deacetylase AtHDA6, to constitute a transcriptional repressor complex. We determined the role of TaHOS15, which might act as an adaptor protein recruiting TaHDA6 to the chromatin of wheat defense-related genes including TaPR1, TaPR2, TaPR5, and TaWRKY45, where they repress histone acetylation. Reduced TaHOS15 or TaHDA6 transcript levels led to decreased susceptibility to Bgt together with enhanced defense-related transcription under Bgt infection. Collectively, these results demonstrate that TaHOS15 functions in a histone deacetylase complex with TaHDA6 to fine-tune the defense response to Bgt in common wheat. [ABSTRACT FROM AUTHOR]

Key message: A new recessive powdery mildew resistance gene, Pm223899, was identified in Afghanistan wheat landrace PI 223899 and mapped to an interval of about 831 Kb in the terminal region of the short arm of chromosome 1A.Abstract: Wheat powdery mildew, a globally important disease caused by the biotrophic fungus Blumeria graminis f.sp. tritici (Bgt), has occurred with increased frequency and severity in recent years, and some widely deployed resistance genes have lost effectiveness. PI 223899 is an Afghanistan landrace exhibiting high resistance to Bgt isolates collected from the Great Plains. An F2 population and F2:3 lines derived from a cross between PI 223899 and OK1059060-126135-3 were evaluated for response to Bgt isolate OKS(14)-B-3-1, and the bulked segregant analysis (BSA) approach was used to map the powdery mildew resistance gene. Genetic analysis indicated that a recessive gene, designated Pm223899, conferred powdery mildew resistance in PI 223899. Linkage analysis placed Pm223899 to an interval of about 831 Kb in the terminal region of chromosome 1AS, spanning 4,504,697-5,336,062 bp of the Chinese Spring reference sequence. Eight genes were predicted in this genomic region, including TraesCS1AG008300 encoding a putative disease resistance protein RGA4. Pm223899 was flanked proximally by a SSR marker STARS333 (1.4 cM) and distally by the Pm3 locus (0.3 cM). One F2 recombinant was identified between Pm3 and Pm223899 using a Pm3b-specific marker, indicating that Pm223899 is most likely a new gene, rather than an allele of the Pm3 locus. Pm223389 confers a high level of resistance to Bgt isolates collected from Pennsylvania, Oklahoma, Nebraska, and Montana. Therefore, Pm223389 can be used to enhance powdery mildew resistance in these states. Pm3b-1 and STARS333 have the potential to tag Pm223389 in wheat breeding. [ABSTRACT FROM AUTHOR]

Background: WD40 domains are abundant in eukaryotes, and they are essential subunits of large multiprotein complexes, which serve as scaffolds. WD40 proteins participate in various cellular processes, such as histone modification, transcription regulation, and signal transduction. WD40 proteins are regarded as crucial regulators of plant development processes. However, the systematic identification and analysis of WD40 proteins have yet to be reported in wheat. Results: In this study, a total of 743 WD40 proteins were identified in wheat, and they were grouped into 5 clusters and 11 subfamilies. Their gene structures, chromosomal locations, and evolutionary relationships were analyzed. Among them, 39 and 46 pairs of TaWD40s were distinguished as tandem duplication and segmental duplication genes. The 123 OsWD40s were identified to exhibit synteny with TaWD40s. TaWD40s showed the specific characteristics at the reproductive developmental stage, and numerous TaWD40s were involved in responses to stresses, including cold, heat, drought, and powdery mildew infection pathogen, based on the result of RNA-seq data analysis. The expression profiles of some TaWD40s in wheat seed development were confirmed through qRT-PCR technique. Conclusion: In this study, 743 TaWD40s were identified from the wheat genome. As the main driving force of evolution, duplication events were observed, and homologous recombination was another driving force of evolution. The expression profiles of TaWD40s revealed their importance for the growth and development of wheat and their response to biotic and abiotic stresses. Our study also provided important information for further functional characterization of some WD40 proteins in wheat. [ABSTRACT FROM AUTHOR]

High-resolution aerial imaging with an unmanned aerial vehicle (UAV) was used to quantify wheat powdery mildew and estimate grain yield. Aerial digital images were acquired at Feekes growth stage (GS) 10.5.4 from flight altitudes of 200, 300, and 400 m during the 2009-10 and 2010-11 seasons; and 50, 100, 200, and 300 m during the 2011-12, 2012-13, and 2013-14 seasons. The image parameter lgR was consistently correlated positively with wheat powdery mildew severity and negatively with wheat grain yield for all combinations of flight altitude and year. Fitting the data with random coefficient regression models showed that the exact relationship of lgR with disease severity and grain yield varied considerably from year to year and to a lesser extent with flight altitude within the same year. The present results raise an important question about the consistency of using remote imaging information to estimate disease severity and grain yield. Further research is needed to understand the nature of interyear variability in the relationship of remote imaging data with disease or grain yield. Only then can we determine how the remote imaging tool can be used in commercial agriculture. [ABSTRACT FROM AUTHOR]

Durable resistance against fungal pathogens is highly valuable for disease management in agriculture. For its sustainable use, and to avoid pathogen adaptation, it is important to understand the underlying molecular mechanisms. Many studies on durable disease resistance in plants have focused exclusively on the host plant, whereas possible reactions and adaptations of pathogens exposed to this type of resistance have not been well researched. The wheat Lr34 gene, encoding a putative ABC‐transporter, provides broad‐spectrum and durable resistance against multiple fungal pathogens in wheat and is functional as a transgene in all major cereals. Lr34‐based resistance is partial, meaning pathogens can grow and reproduce to some degree on Lr34‐containing plants. Therefore, Lr34‐expressing plants are ideal for studying the response of pathogens to partial resistance. Here, transcriptomic responses of the two fungal pathogens Blumeria graminis f. sp. hordei (barley powdery mildew) and Puccinia triticina (wheat leaf rust) during growth on their respective host plants containing Lr34 were compared to their responses on control plants without Lr34. Two different time points after inoculation were chosen for analysis of powdery mildew on barley and one time point for wheat leaf rust. Transcriptome analyses revealed that there were no differences in the expression patterns of the two pathogens growing on susceptible versus partially resistant plants, even though pathogen growth was reduced in the presence of Lr34. This reflects the absence of observable reaction in the pathogen to the presence of the Lr34 resistance gene and, consequently, no major alteration of fungal pathogen metabolism. [ABSTRACT FROM AUTHOR]

Summary: Recognition of the AVRPM3A2/F2 avirulence protein from powdery mildew by the wheat PM3A/F immune receptor induces a hypersensitive response after co‐expression in Nicotiana benthamiana. The molecular determinants of this interaction and how they shape natural AvrPm3a2/f2 allelic diversity are unknown. We sequenced the AvrPm3a2/f2 gene in a worldwide collection of 272 mildew isolates. Using the natural polymorphisms of AvrPm3a2/f2 as well as sequence information from related gene family members, we tested 85 single‐residue‐altered AVRPM3A2/F2 variants with PM3A, PM3F and PM3FL456P/Y458H (modified for improved signaling) in Nicotiana benthamiana for effects on recognition. An intact AvrPm3a2/f2 gene was found in all analyzed isolates and the protein variant recognized by PM3A/F occurred globally at high frequencies. Single‐residue alterations in AVRPM3A2/F2 mostly disrupted, but occasionally enhanced, the recognition response by PM3A, PM3F and PM3FL456P/Y458H. Residues enhancing hypersensitive responses constituted a protein domain separate from both naturally occurring polymorphisms and positively selected residues of the gene family. These results demonstrate the utility of using gene family sequence diversity to screen residues for their role in recognition. This approach identified a putative interaction surface in AVRPM3A2/F2 not polymorphic in natural alleles. We conclude that molecular mechanisms besides recognition drive AvrPm3a2/f2 diversification. [ABSTRACT FROM AUTHOR]

Summary: Powdery mildew is one of the most devastating diseases of wheat. To date, few powdery mildew resistance genes have been cloned from wheat due to the size and complexity of the wheat genome. Triticum urartu is the progenitor of the A genome of wheat and is an important source for powdery mildew resistance genes. Using molecular markers designed from scaffolds of the sequenced T. urartu accession and standard map‐based cloning, a powdery mildew resistance locus was mapped to a 356‐kb region, which contains two nucleotide‐binding and leucine‐rich repeat domain (NB‐LRR) protein‐encoding genes. Virus‐induced gene silencing, single‐cell transient expression, and stable transformation assays demonstrated that one of these two genes, designated Pm60, confers resistance to powdery mildew. Overexpression of full‐length Pm60 and two allelic variants in Nicotiana benthamiana leaves induced hypersensitive cell death response, but expression of the coiled‐coil domain alone was insufficient to induce hypersensitive response. Yeast two‐hybrid, bimolecular fluorescence complementation and luciferase complementation imaging assays showed that Pm60 protein interacts with its neighboring NB‐containing protein, suggesting that they might be functionally related. The identification and cloning of this novel wheat powdery mildew resistance gene will facilitate breeding for disease resistance in wheat. [ABSTRACT FROM AUTHOR]

Key message: The combined effects of enhanced total transgene expression level and allele-specificity combination in transgenic allele-pyramided Pm3 wheat lines result in improved powdery mildew field resistance without negative pleiotropic effects.Abstract: Allelic Pm3 resistance genes of wheat confer race-specific resistance to powdery mildew (Blumeria graminis f. sp. tritici, Bgt) and encode nucleotide-binding domain, leucine-rich repeat (NLR) receptors. Transgenic wheat lines overexpressing alleles Pm3a, b, c, d, f, and g have previously been generated by transformation of cultivar Bobwhite and tested in field trials, revealing varying degrees of powdery mildew resistance conferred by the transgenes. Here, we tested four transgenic lines each carrying two pyramided Pm3 alleles, which were generated by crossbreeding of lines transformed with single Pm3 alleles. All four allele-pyramided lines showed strongly improved powdery mildew resistance in the field compared to their parental lines. The improved resistance results from the two effects of enhanced total transgene expression levels and allele-specificity combinations. In contrast to leaf segment tests on greenhouse-grown seedlings, no allelic suppression was observed in the field. Plant development and yield scores of the pyramided lines were similar to the mean scores of the corresponding parental lines, and thus, the allele pyramiding did not cause any negative effects. On the contrary, in pyramided line, Pm3b × Pm3f normal plant development was restored compared to the delayed development and reduced seed set of parental line Pm3f. Allele-specific RT qPCR revealed additive transgene expression levels of the two Pm3 alleles in the pyramided lines. A positive correlation between total transgene expression level and powdery mildew field resistance was observed. In summary, allele pyramiding of Pm3 transgenes proved to be successful in enhancing powdery mildew field resistance. [ABSTRACT FROM AUTHOR]

It is necessary to quantitatively identify different diseases and nitrogen-water stress for the guidance in spraying specific fungicides and fertilizer applications. The winter wheat diseases, in combination with nitrogen-water stress, are therefore common causes of yield loss in winter wheat in China. Powdery mildew (Blumeria graminis) and stripe rust (Puccinia striiformis f. sp. Tritici) are two of the most prevalent winter wheat diseases in China. This study investigated the potential of continuous wavelet analysis to identify the powdery mildew, stripe rust and nitrogen-water stress using canopy hyperspectral data. The spectral normalization process was applied prior to the analysis. Independent t-tests were used to determine the sensitivity of the spectral bands and vegetation index. In order to reduce the number of wavelet regions, correlation analysis and the independent t-test were used in conjunction to select the features of greatest importance. Based on the selected spectral bands, vegetation indices and wavelet features, the discriminate models were established using Fisher's linear discrimination analysis (FLDA) and support vector machine (SVM). The results indicated that wavelet features were superior to spectral bands and vegetation indices in classifying different stresses, with overall accuracies of 0.91, 0.72, and 0.72 respectively for powdery mildew, stripe rust and nitrogen-water by using FLDA, and 0.79, 0.67 and 0.65 respectively by using SVM. FLDA was more suitable for differentiating stresses in winter wheat, with respective accuracies of 78.1%, 95.6% and 95.7% for powdery mildew, stripe rust, and nitrogen-water stress. Further analysis was performed whereby the wavelet features were then split into high-scale and low-scale feature subsets for identification. The accuracies of high-scale and low-scale features with an overall accuracy (OA) of 0.61 and 0.73 respectively were lower than those of all wavelet features with an OA of 0.88. The detection of the severity of stripe rust using this method showed an enhanced reliability (R2 =0.828). [ABSTRACT FROM AUTHOR]

Small unmanned aerial vehicle (UAV), a timely and effective pesticide sprayer, can be used to spray pesticide in a high efficiency without harming the crop, and is especially suitable for spraying for small farms and hills in Asian countries. In recent years, it has been chosen as a key and new technique for pesticide application. This paper studied the impact of UAV (UAV N-3) spraying parameters (different working height and different spraying concentrations) on the deposition of droplets on the wheat canopy and the prevention of powdery mildew. Water sensitive paper was used as the sampler to collect the pesticide droplets and image processing software Deposit Scan was used to compute the coverage rate of droplets on the wheat top layer to acquire the proportional distribution of droplets on the wheat lower layer. The experimental results showed the impact of spraying height on the distribution of droplets on the wheat upper layer was quite significant, when the spraying height was 5.0 m and the spraying speed was 4 m/s, the coverage rate of droplets on the wheat lower layer was the largest, as it was 45.6% of that on the upper layer, the droplets distribution was the most uniform, and the coefficient of variation was 33.13%. 450 g/hm2 (dosage registered) of triadimefon SC (44%) was sprayed by the UAV, the control efficiency reached 55.1% after applying which was better than 20% and 40% of dosage decreased for each hectare, and the applying effect (35.6%) of 20% dosage decreased for each hectare had no significant difference from the applying effect (34.6%) applied by a knapsack-type electric sprayer. At 10 d after applying, the prevention effect realized by UAV was lower than that realized by a knapsack-type electric sprayer, and it may be correlated to the meteorological condition and water amount in the pesticide sprayed. Thus, when UAV spraying was chosen to prevent wheat powdery mildew under a serious disease situation, an auxiliary agent for spraying could be added to prolong the retention of pesticide on the plant surface to extend the pesticide effect. This study can provide a reference for the optimized design, performance upgrade and reasonable application of small UAV sprayers. [ABSTRACT FROM AUTHOR]

Monitoring of wheat crop, pre and post harvest, was done for recording incidence of various diseases in Punjab state during the period 2013-14 to 2015-16. The data indicated a change in virulence of stripe rust pathogen among the pre harvest diseases, whereas, among the post harvest diseases, Karnal bunt, a minor disease earlier, has become a matter of concern as its incidence has increased over the years (highest 2.20% in 2014-15). The trend is considered mainly due to prevalence of favourable environmental conditions during the most vulnerable growth stage of the crop. [ABSTRACT FROM AUTHOR]

The biotroph wheat powdery mildew, Blumeria graminis (DC.) E.O. Speer, f. sp. tritici Em. Marchal (Bgt), has undergone long and dynamic co-evolution with its hosts. In the last 10,000 years, processes involved in plant evolution under domestication, altered host-population structure. Recently both virulence and genomic profiling separated Bgt into two groups based on their origin from domestic host and from wild emmer wheat. While most studies focused on the Bgt pathogen, there is significant knowledge gaps in the role of wheat host diversity in this specification. This study aimed to fill this gap by exploring qualitatively and also quantitatively the disease response of diverse host panel to powdery mildew [105 domesticated wheat genotypes (Triticum turgidum ssp. dicoccum, T. turgidum ssp. durum, and T. aestivum) and 241 accessions of its direct progenitor, wild emmer wheat (T. turgidum ssp. dicoccoides)]. A set of eight Bgt isolates, originally collected from domesticated and wild wheat was used for screening this wheat collection. The isolates from domesticated wheat elicited susceptible to moderate plant responses on domesticated wheat lines and high resistance on wild genotypes (51.7% of the tested lines were resistant). Isolates from wild emmer elicited reciprocal disease responses: high resistance of domesticated germplasmand high susceptibility of the wild material (their original host). Analysis of variance of the quantitative phenotypic responses showed a significant Isolates × Host species interaction [P(F) < 0.0001] and further supported these findings. Furthermore, analysis of the range of disease severity values showed that when the group of host genotypes was inoculated with Bgt isolate from the reciprocal host, coefficient of variation was significantly higher than when inoculated with its own isolates. This trend was attributed to the role of major resistance genes in the latter scenario (high proportion of complete resistance). By testing the association between disease severity and geographical distance from the source of inoculum, we have found higher susceptibility in wild emmer close to the source. Both qualitative and quantitative assays showed a reciprocal resistance pattern in the wheat host and are well aligned with the recent findings of significant differentiation into wild-emmer and domesticated-wheat populations in the pathogen. [ABSTRACT FROM AUTHOR]

Powdery mildew resistance gene Pm4b, originating from Triticum persicum, is effective against the prevalent Blumeria graminis f. sp. tritici (Bgt) isolates from certain regions of wheat production in China. The lack of tightly linked molecular markers with the target gene prevents the precise identification of Pm4b during the application of molecular marker-assisted selection (MAS). The strategy that combines the RNA-Seq technique and the bulked segregant analysis (BSR-Seq) was applied in an F2:3 mapping population (237 families) derived from a pair of isogenic lines VPM1/7*Bainong 3217 F4 (carrying Pm4b) and Bainong 3217 to develop more closely linked molecular markers. RNA-Seq analysis of the two phenotypically contrasting RNA bulks prepared from the representative F2:3 families generated 20,745,939 and 25,867,480 high-quality read pairs, and 82.8 and 80.2% of them were uniquely mapped to the wheat whole genome draft assembly for the resistant and susceptible RNA bulks, respectively. Variant calling identified 283,866 raw single nucleotide polymorphisms (SNPs) and InDels between the two bulks. The SNPs that were closely associated with the powdery mildew resistance were concentrated on chromosome 2AL. Among the 84 variants that were potentially associated with the disease resistance trait, 46 variants were enriched in an about 25 Mb region at the distal end of chromosome arm 2AL. Four Pm4b-linked SNP markers were developed from these variants. Based on the sequences of Chinese Spring where these polymorphic SNPs were located, 98 SSR primer pairs were designed to develop distal markers flanking the Pm4b gene. Three SSR markers, Xics13, Xics43, and Xics76, were incorporated in the new genetic linkage map, which located Pm4b in a 3.0 cM genetic interval spanning a 6.7 Mb physical genomic region. This region had a collinear relationship with Brachypodium distachyon chromosome 5, rice chromosome 4, and sorghum chromosome 6. Seven genes associated with disease resistance were predicted in this collinear genomic region, which included C2 domain protein, peroxidase activity protein, protein kinases of PKc_like super family, Mlo family protein, and catalytic domain of the serine/threonine kinases (STKc_IRAK like super family). The markers developed in the present study facilitate identification of Pm4b during its MAS practice. [ABSTRACT FROM AUTHOR]

Abstract: The hormone jasmonate (JA) signalling pathway is involved in diverse developmental processes in plants. COI1 is a key regulator in JA pathway. Although COI1 homologous proteins have been identified in a variety of crops, their regulatory mechanisms in wheat defence responses remain unknown. Here, we cloned COI1 from disease resistant wheat Brock, designated TaCOI1. TaCOI1 cDNA was 1988‐bp long, with an ORF encoding 593 deduced amino acids. The phylogenetic tree showed that TaCOI1 was clustered in the same clade of monocotyledons. The predicted protein possesses an F‐box domain, several LRRs and a conserved AMN1 domain. Its transcription was induced in the compatible and incompatible wheat by Blumeria graminis f. sp. tritici (Bgt) fungus, with differences observed in response time. Expression pattern analysis in the susceptible wheat variety Jing411 revealed that TaCOI1 was up‐regulated after Bgt inoculation at 12‐hour postinoculation (hpi). While, in Brock its transcription was rapidly induced and reached a first peak at 2 hpi. These results suggest that TaCOI1 may be involved in the early response to powdery mildew. The expression of TaCOI1 was decreased by virus‐induced gene silencing. The rate of successful penetration by Bgt was higher in all TaCOI1‐silenced Brock, while the percentage of macrocephalic appressoria and resistance reactions was lower than control. These results suggest that silencing of the TaCOI1 gene increased Brock susceptibility to infection. Together, these findings indicate that the TaCOI1 gene could be involved in the early defence response against wheat powdery mildew and may play an important role in wheat–Bgt interactions. [ABSTRACT FROM AUTHOR]

Summary: Plant sense potential microbial pathogen using pattern recognition receptors (PRRs) to recognize pathogen‐associated molecular patterns (PAMPs). The Lectin receptor‐like kinase genes (LecRKs) are involved in various cellular processes mediated by signal transduction pathways. In the present study, an L‐type lectin receptor kinase gene LecRK‐V was cloned from Haynaldia villosa, a diploid wheat relative which is highly resistant to powdery mildew. The expression of LecRK‐V was rapidly up‐regulated by Bgt inoculation and chitin treatment. Its transcript level was higher in the leaves than in roots, culms, spikes and callus. Single‐cell transient overexpression of LecRK‐V led to decreased haustorium index in wheat variety Yangmai158, which is powdery mildew susceptible. Stable transformation LecRK‐V into Yangmai158 significantly enhanced the powdery mildew resistance at both seedling and adult stages. At seedling stage, the transgenic line was highly resistance to 18 of the tested 23 Bgt isolates, hypersensitive responses (HR) were observed for 22 Bgt isolates, and more ROS at the Bgt infection sites was accumulated. These indicated that LecRK‐V confers broad‐spectrum resistance to powdery mildew, and ROS and SA pathways contribute to the enhanced powdery mildew resistance in wheat. [ABSTRACT FROM AUTHOR]

Efficacy of five systemic fungicides (flusilazole, propiconazole, diniconazole, cyproconazole and tetraconazol) in curbing powdery mildew disease of wheat (Sakha93) and its impact on yield components were evaluated under field condition during two successive season. Both fungicides, propiconazole and diniconazole exhibited the highest value of efficacy (88.80% each) recording the lowest rate of disease infection (1 each). The contrast was noticed with tetraconazol (55.50% efficacy, four disease infection) with significant differences to untreated control during both seasons. The results of fungicide application reflected on yield components where 1000-kernel and 1000-mL weights recorded the highest values with propiconazole (49.03 g and 742.65 g) followed by diniconazole (47.69 g and 737.62 g), respectively. Tetraconazol come in the last order in this respect (44.39 g and 672.07 g). An active role of fungicide (propiconazole) on Blumeria graminis f. sp. tritici was examined on infected wheat leaves (eight-day old seedlings) by scanning electron microscopy (SEM). To investigate the effect on early develop of conidia, fungicide was applied at 24 h post inoculation (hpi), and collapsed conidia along with blocked development beyond the primary appressoria were observed. Where conidia germinated, appressoria formed two or three lobes. To investigate the effect on fungal morphogenesis, applying of fungicide at 2 day post inoculation (dpi) greatly reduced the mycelium formation associated with a rapid collapse of hyphae compared with untreated control. Fungicide treatment at 10 dpi inhibited and delayed sporulation alongside formation of aberrant and collapsed conidiophores. The conidiophores formed elongated tubes with no regular or sepatated chain of conidiospores. Results concluded that fungicide is an efficient curative fungicide at very low concentrations if it is applied early enough after infection. Also, fungicide has a significant impact on fungal survival. [ABSTRACT FROM AUTHOR]

A key member of the Pm21 resistance gene locus, Stpk-V, derived from Haynaldia villosa, was shown to confer broad-spectrum resistance to wheat powdery mildew. The present study was planned to investigate the resistance mechanism mediated by Stpk-V., Transcriptome analysis was performed in Stpk-V transgenic plants and recipient Yangmai158 upon Bgt infection, and detailed histochemical observations were conducted. Chromosome location of Stpk-V orthologous genes in Triticeae species was conducted for evolutionary study and over-expression of Stpk-V both in barley and Arabidopsis was performed for functional study., The transcriptome results indicate, at the early infection stage, the ROS pathway, JA pathway and some PR proteins associated with the SA pathway were activated in both the resistant Stpk-V transgenic plants and susceptible Yangmai158. However, at the later infection stage, the genes up-regulated at the early stage were continuously held only in the transgenic plants, and a large number of new genes were also activated in the transgenic plants but not in Yangmai158., Results indicate that sustained activation of the early response genes combined with later-activated genes mediated by Stpk-V is critical for resistance in Stpk-V transgenic plants. Stpk-V orthologous genes in the representative grass species are all located on homologous group six chromosomes, indicating that Stpk-V is an ancient gene in the grasses. Over-expression of Stpk-V enhanced host resistance to powdery mildew in barley but not in Arabidopsis. Our results enable a better understanding of the resistance mechanism mediated by Stpk-V, and establish a solid foundation for its use in cereal breeding as a gene resource. [ABSTRACT FROM AUTHOR]

Rye (Secale cereale L.) 4R chromosome contains elite genes that are applicable for wheat (Triticum aestivum L.) cultivar improvement. PCR-based 4R-specific markers can benefit the detection of elite genes on 4R in wheat backgrounds. In this study, a new fluorescence in situ hybridization (FISH) map of the 4RKu chromosome of rye Kustro has been constructed. A set of 4RKu dissection lines was obtained and 301 new 4RKu-specific markers were developed using specific length amplified fragment sequencing (SLAF-seq) technology. These markers were combined with the 99 4RKu-specific markers previously developed, and were physically mapped to 4RKu chromosome using the new FISH map and the 4RKu dissection lines. A total of 338 of the 400 markers have been successfully mapped to six regions of 4RKu chromosome. Additionally, the powdery mildew resistance gene(s) on the 4RLKu arm was located to the segment between L.4 and L.8, the same region where 115 4RLKu-specific markers were mapped. The markers developed in this study can be used to identify a specific segment of 4R chromatin in wheat backgrounds, help construct a high-density physical map of 4R chromosome, and facilitate the utilization of elite genes on 4R chromosome in wheat breeding programs. [ABSTRACT FROM AUTHOR]

Agropyron elongatum (Host.) Neviski (synonym, Thinopyrum ponticum Podp., 2n = 70) has been used extensively as a valuable source for wheat breeding. Numerous chromosome fragments containing valuable genes have been successfully translocated into wheat from A. elongatum. However, reports on the transfer of powdery mildew resistance from A. elongatum to wheat are rare. In this study, a novel wheat-A. elongatum translocation line, 11-20-1, developed and selected from the progenies of a sequential cross between wheat varieties (Lankaoaizaoba, Keyu 818 and BainongAK 58) and A. elongatum, was evaluated for disease resistance and characterized using molecular cytogenetic methods. Cytological observations indicated that 11-20-1 had 42 chromosomes and formed 21 bivalents at meiotic metaphase I. Genomic in situ hybridization analysis using whole genomic DNA from A. elongatum as a probe showed that the short arms of a pair of wheat chromosomes were replaced by a pair of A. elongatum chromosome arms. Fluorescence in situ hybridization, using wheat D chromosome specific sequence pAs1 as a probe, suggested that the replaced chromosome arms of 11-20-1 were 5DS. This was further confirmed by wheat SSR markers specific for 5DS. EST-SSR and EST-STS multiple loci markers confirmed that the introduced A. elongatum chromosome arms belonged to homoeologous group 5. Therefore, it was deduced that 11-20-1 was a wheat-A. elongatum T5DL∙5AgS translocation line. Both resistance observation and molecular marker analyses using two specific markers (BE443538 and CD452608) of A. elongatum in a F2 population from a cross between line 11-20-1 and a susceptible cultivar Yannong 19 verified that the A. elongatum chromosomes were responsible for the powdery mildew resistance. This work suggests that 11-20-1 likely contains a novel resistance gene against powdery mildew. We expect this line to be useful for the genetic improvement of wheat. [ABSTRACT FROM AUTHOR]

Wheat ( Triticum aestivum L.) incurs significant yield losses from powdery mildew, a major fungal disease caused by Blumeria graminis f. sp. tritici ( Bgt). enhanced disease resistance1 ( EDR1) plays a negative role in the defense response against powdery mildew in Arabidopsis thaliana; however, the edr1 mutant does not show constitutively activated defense responses. This makes EDR1 an ideal target for approaches using new genome-editing tools to improve resistance to powdery mildew. We cloned Ta EDR1 from hexaploid wheat and found high similarity among the three homoeologs of EDR1. Knock-down of Ta EDR1 by virus-induced gene silencing or RNA interference enhanced resistance to powdery mildew, indicating that Ta EDR1 negatively regulates powdery mildew resistance in wheat. We used CRISPR/Cas9 technology to generate Taedr1 wheat plants by simultaneous modification of the three homoeologs of wheat EDR1. No off-target mutations were detected in the Taedr1 mutant plants. The Taedr1 plants were resistant to powdery mildew and did not show mildew-induced cell death. Our study represents the successful generation of a potentially valuable trait using genome-editing technology in wheat and provides germplasm for disease resistance breeding. [ABSTRACT FROM AUTHOR]

At present, most of released wheat cultivars or breeding lines in China are susceptible to powdery mildew (Pm) (caused by Blumeria graminis f. sp. tritici, Bgt), so there is an urgent need to rapidly transfer effective and broad-spectrum Pm resistance genes into elite cultivars/lines. Near-isogenic lines (NILs) with short target gene region are very important in molecular breeding and map-based cloning and can be developed by combining marker-assisted selection and conventional phenotypic identification. However, no Pm gene NILs were reported by using this method in the previous studies. A new broad-spectrum dominant resistance gene Pm2b, derived from the Chinese wheat breeding line KM2939, conferred high resistance to Pm at both the seedling and adult stages. In this study, with the aid of forward and background selection (FS and BS) using molecular markers, the Pm2b gene was introgressed into three elite susceptible commercial cultivars Shimai 15, Shixin 828, and Kenong 199 through the back-crossing procedure. With the appropriate backcrossing generations, selected population sizes and marker number for BS, the homozygous resistant BC3F2:3 NILs of Pm2b gene in the three genetic backgrounds with the highest recipient genome composition of about 99%, confirmed by simple sequence repeat markers and 660K single nucleotide polymorphic array, were developed and evaluated for the powdery mildew resistance and agronomic traits. The different resistance and similar or improved agronomic performance between Pm2b NILs and their corresponding recurrent parents indicated their potential value in the marker-assisted breeding of the Pm2b gene. Moreover, the development of four flanked diagnostic markers (CFD81, BWM25, BWM20, and BWM21) of the Pm2 gene can effectively assist the forward selection and accelerate the transfer and use of this resistance gene. [ABSTRACT FROM AUTHOR]

Key message: A novel powdery mildew-resistance gene, designated Pm58, was introgressed directly from Aegilops tauschii to hexaploid wheat, mapped to chromosome 2DS, and confirmed to be effective under field conditions. Selectable KASP™ markers were developed for MAS. Abstract: Powdery mildew caused by Blumeria graminis (DC.) f. sp. tritici ( Bgt) remains a significant threat to wheat ( Triticum aestivum L.) production. The rapid breakdown of race-specific resistance to Bgt reinforces the need to identify novel sources of resistance. The d-genome species, Aegilops tauschii, is an excellent source of disease resistance that is transferrable to T. aestivum. The powdery mildew-resistant Ae. tauschii accession TA1662 (2 n = 2 x = DD) was crossed directly with the susceptible hard white wheat line KS05HW14 (2 n = 6 x = AABBDD) followed by backcrossing to develop a population of 96 BCF introgression lines (ILs). Genotyping-by-sequencing was used to develop a genome-wide genetic map that was anchored to the Ae. tauschii reference genome. A detached-leaf Bgt assay was used to screen BCF ILs, and resistance was found to segregate as a single locus ( χ = 2.0, P value = 0.157). The resistance gene, referred to as Pm58, mapped to chromosome 2DS. Pm58 was evaluated under field conditions in replicated trials in 2015 and 2016. In both years, a single QTL spanning the Pm58 locus was identified that reduced powdery mildew severity and explained 21% of field variation ( P value < 0.01). KASP™ assays were developed from closely linked GBS-SNP markers, a refined genetic map was developed, and four markers that cosegregate with Pm58 were identified. This novel source of powdery mildew-resistance and closely linked genetic markers will support efforts to develop wheat varieties with powdery mildew resistance. [ABSTRACT FROM AUTHOR]

Powdery mildew is one of the most important diseases of wheat. In this study, the leaf RNA samples of wheat NILs carrying powdery mildew resistant and susceptible Pm2 alleles (L031 and Chancellor) and its F1 hybrid at two time points (16 h and 96 h postinoculation) were used for RNA-seq analysis. We carry comparison between similar materials at different times and between different materials at same times. The overlapping DEGs between the dominant phenotypes (L031 and F1 hybrid) and the recessive phenotype (Chancellor) were 1028 and 2214 DEGs, which were clearly lower than those between the dominant and recessive parents and thus could provide relatively accurate and valuable information. GO and KEGG enrichment analysis of DEGs revealed that other than the expected defense-related genes, differential up- and downregulation of genes from many other signaling networks were also involved. Comparative transcriptome analysis also revealed that early-stage postinoculation is important and suitable time points to study expression profiles and signaling pathways of resistance-related genes following fungal inoculation. qRT-PCR analyses showed highly consistent expression patterns of genes with RNA-seq data. The results will aid in the identification of genes and signaling pathways involved in powdery mildew response in wheat. [ABSTRACT FROM AUTHOR]

Powdery mildew, caused by Blumeria graminis f.sp. tritici, is a major wheat disease in maritime and temperate climates. Breeding for race-non-specific or partial resistance is a cost-effective and environmentally friendly disease control strategy. The German spring wheat cultivar Naxos has proven to be a good source for partial resistance to powdery mildew. The objectives of the present study were to map the resistance loci in Naxos with use of high-density SNP markers in the Shanghai3/Catbird x Naxos inbred line population and validate the results in a different genetic background; Soru#1 x Naxos. Both populations were genotyped with the Illumina iSelect 90K wheat chip, and integrated linkage maps developed by inclusion of previously genotyped SSR and DArT markers. With the new linkage maps, we detected a total of 12 QTL for powdery mildew resistance in Shanghai3/Catbird x Naxos, of which eight were derived from Naxos. Previously reported QTL on chromosome arms 1AS and 2BL were more precisely mapped and the SNP markers enabled discovery of new QTL on 1AL, 2AL, 5AS and 5AL. In the Soru#1 x Naxos population, four QTL for powdery mildew resistance were detected, of which three had resistance from Naxos. This mapping verified the 1AS and 2AL QTL detected in Shanghai3/Catbird x Naxos, and identified a new QTL from Naxos on 2BL. In conclusion, the improved linkage maps with SNP markers enabled discovery of new resistance QTL and more precise mapping of previously known QTL. Moreover, the results were validated in an independent genetic background. [ABSTRACT FROM AUTHOR]

Bacillus velezensis CC09, which was isolated from healthy leaves of Cinnamomum camphora and previously identified as Bacillus amyloliquefaciens CC09, shows great potential as a new biocontrol agent, in control of many phytopathogenic diseases. To extend our understanding of the potential antifungal capacities, we did a whole genome analysis of strain CC09. Result shows that strain CC09 has a relatively large genome size (4.17 Mb) with an average GC content of 46.1%, and 4021 predicted genes. Thirteen secondary metabolites encoding clusters have been identified within the genome of B. velezensis CC09 using genome mining technique. Data of comparative genomic analysis indicated that 3 of the clusters are conserved by all strains of B. velezensis , B. amyloliquefaciens and B. subtilis 168, 9 by B. velezensis and B. amyloliquefaciens , and 2 by all strains of B. velezensis . Another 2 clusters encoding NRPS (Non-Ribosomal Peptide Synthetases) and NRPS-TransATPKS (NRPS and trans -Acyl Transferase Polyketide Synthetases) respectively are observed only in 15 B. velezensis strains, which might lead to the synthesis of novel bioactive compounds and could be explored as antimicrobial agents in the future. These clusters endow B. velezensis CC09 with strong and broad antimicrobial activities, for example, in control of wheat powdery mildew disease. Moreover, our data further confirmed the taxonomy of strain CC09 is a member of B. velezensis rather than a strain of B. amyloliquefaciens based on core genome sequence analysis using phylogenomic approach. [ABSTRACT FROM AUTHOR]

Wheat is one of the most widely grown cereal crops in the world and is an important food grain source for humans. However, wheat yields can be reduced by many abiotic and biotic stress factors, including powdery mildew disease caused by Blumeria graminis f.sp. tritici ( Bgt). Generating resistant varieties is thus a major effort in plant breeding. Here, we took advantage of the non-transgenic Targeting Induced Lesions IN Genomes ( TILLING) technology to select partial loss-of-function alleles of TaMlo, the orthologue of the barley Mlo ( Mildew resistance locus o) gene. Natural and induced loss-of-function alleles ( mlo) of barley Mlo are known to confer durable broad-spectrum powdery mildew resistance, typically at the expense of pleiotropic phenotypes such as premature leaf senescence. We identified 16 missense mutations in the three wheat TaMlo homoeologues, TaMlo- A1, TaMlo- B1 and TaMlo- D1 that each lead to single amino acid exchanges. Using transient gene expression assays in barley single cells, we functionally analysed the different missense mutants and identified the most promising candidates affecting powdery mildew susceptibility. By stacking of selected mutant alleles we generated four independent lines with non-conservative mutations in each of the three TaMlo homoeologues. Homozygous triple mutant lines and surprisingly also some of the homozygous double mutant lines showed enhanced, yet incomplete, Bgt resistance without the occurrence of discernible pleiotropic phenotypes. These lines thus represent an important step towards the production of commercial non-transgenic, powdery mildew-resistant bread wheat varieties. [ABSTRACT FROM AUTHOR]

Thinopyrum ponticum (2 n=70) serves as a valuable gene pool for wheat improvement. Line SN0224, derived from crosses between Th. ponticum and the common wheat cultivar Yannong15, was identified in the present study. Cytogenetic observations showed that SN0224 contains 42 chromosomes in the root-tip cells and 21 bivalents in the pollen mother cells, thereby demonstrating its cytogenetic stability. Genomic in situ hybridization, probed with the total genomic DNA of Th. ponticum, produced hybridization signals in the distal region of two wheat chromosome arms. After inoculation with the Blumeria graminis f. sp. tritici ( Bgt) isolates, SN0224 exhibited immunity. Segregation in F s and F s from the cross SN0224/cv. Huixianhong indicated that SN0224 carries a single dominant gene for powdery mildew (Pm) resistance, which was temporarily designated PmSn0224. Three markers Barc212, Xwmc522 and Xbarc1138 were detected to be linked with PmSn0224. Based on the locations of the markers, PmSn0224 was located on the chromosome 2A. None of the three markers above is linked with the previously reported PM resistance genes on chromosome 2A, and none of the previously reported PM resistance genes on chromosome 2A is related to Th. ponticum. Therefore, PmSn0224 is likely a novel gene putatively from Th. ponticum. [ABSTRACT FROM AUTHOR]

Leaf rust (LR) and stripe rust (YR) are important diseases of wheat worldwide. We used 148 recombinant inbred lines (R1L) from the cross of Avocet × Kundan for determining and mapping the genetic basis of adult plant resistance (APR) loci. The population was phenotyped LR and YR for three seasons in field trials conducted in Mexico and genotyped with the diversity arrays technology sequencing (DArT-Seq) and simple sequence repeat markers. The final genetic map was constructed using 2,937 polymorphic markers with an average distance of 1.29 centimorgans between markers. Inclusive composite interval mapping identified two co-located APR quantitative trait loci (QTL) for LR and YR, two LR QTL, and three YR QTL. The co-located resistance QTL on chromosome 1BL corresponded to the pleiotropic APR gene Lr46/Yr29. QLr.cim-2BL, QYr.cim-2AL, and QYr.cim-5AS could be identified as new resistance loci in this population. Lr46/Yr29 contributed 49.5 to 65.1 and 49.2 to 66.1% of LR and YR variations, respectively. The additive interaction between detected QTL showed that LR severities for RIL combining four QTL ranged between 5.3 and 25.8%, whereas the lowest YR severities were for RIL carrying QTL on chromosomes 1BL + 2AL + 6AL. The high-density DArT-Seq markers across chromosomes can be used in fine mapping of the targeted loci and development SNP markers. [ABSTRACT FROM AUTHOR]

This stiady aimed to know the resistance to powdery mildew of major Pm genes used in China，and Chinese wheat commercial cultivars ，as well as foreign wheat materials. Field monitoring of 6 Pm genes，46 Chinese wheat cultivars and 66 foreign wheat materials in Li- cang，Dehong，Dali，Yuxi，Kunming and Zhaotong，Yunnan province had been carried out by natural identification during 2012 and 2013. The results indicated that the resistance of the 6 Pm genes had been lost gradually，decrease of the area of wheat carrying Pm8 and Pm21 is urgent. Pm2，Pm4a，Pm4b and Pm2 +6 should be used rationaiy. The resistance level of Chinese wheat commercial cultivar is very low. Among 46 cultivars，none of which showed resistant at 6 sites during the two years in Yunnan，6 cultivars showed susceptible only at one site，18 cultivars showed susceptible at 2 sites，22 cultivarr showed susceptible at 3 sites. Among 66 foreign wheat materials，only Hybrid 46 and Heines Kolben showed resistant at 6 sites during the 2 yearr in Yunnan，which indicated stable resistant. Seven materials showed susceptible only at 1 site，29 materials showed susceptible at 2 sites，28 materials showed susceptible at 3 sites. Those results indicated the lack of resistance sources and cultivars in China at present. Looking for new resistance sources and breeding new resistance cultivars are very urgent. The pressing matter of the moment is strengthening monitoring and emergency control， to ensure wheat security. [ABSTRACT FROM AUTHOR]

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