Resistant Wheat Cultivars Research Articles

Meta-analysis highlights the key drought responsive genes in genes: PEPC and TaSAG7 are hubs response networks

BackgroundWheat is the most important cereal. One of the environmental stresses is drought that harm the production of many cereals and every year due to low rainfall and frequent droughts, the need to produce plants resistant to this stress is felt. Therefore, identification and evaluation of the genes involved in the production of this resistance in plants are of great importance. By identifying these genes and changing their expression, it is possible to produce resistant plants that can tolerate dehydration and drought, with at least a qualitative and quantitative reduction in yield. ResultsBased on the meta-analysis results obtained in this study, in resistant cultivars ~ 4% (2394/61290) of the probe IDs decreased and ~ 4.5% (2670/61290) increased expression, furthermore in susceptible cultivars ~ 7% (4183/61290) of probe IDs decreased and ~ 6% (3591/61290) increased expression (P value ≤ 0.05). List of up- and downregulated genes was revealed, among the expressed genes of transcription factors Myb3, ethylene-responsive 5a, MIKC-type MADS-box WM24B, and salinity inducible ERF4 in resistant cultivars and transcription factors WRKY15, MADS-box TaAGL8, WRKY39, and Myb in susceptible cultivars, they showed a significant increase in expression, these transcription factors are of great importance in drought stress. Among them, ethylene responsive 5a in resistant cultivars by 3 times and Myb in susceptible cultivars by 2.6 times have shown the highest expression change. Using Cytoscape Hub software, the Phosphoenolpyruvate carboxylase (PEPC) and lyase isocitrate (TaSAG7) genes, which have significantly different expressions in resistant and susceptible wheat cultivars. PEPC and TaSAG7 genes were upregulated in resistant wheat cultivars as well as down regulated in susceptible cultivars. Also, the qPCR results of selected genes were consistent with the outcomes of the meta-analysis. ConclusionsAll microarray data were collected from the NCBI Gene Expression Omnibus site. Libraries with drought-tolerant and susceptible cultivars for wheat were considered under the stress and control conditions from whole leaf tissue. By meta-analysis combined the purposeful results of multiple experiments, and found list of genes expressed in reverse between the two cultivars. These genes can distinguish between different susceptible and resistant wheat cultivars.

Evaluation of Seedling Resistance and Marker Assisted Selection for Leaf Rust (Puccinia triticina) Resistance in Pakistani Wheat Landraces, Cultivars and Advanced Lines

Leaf rust is amongst major biotic constraints of wheat (Triticum aestivum L.) having ability to cause substantial yield reductions worldwide. A continuous exploration for novel sources of resistance is pre-requisite for its management. Objectives of study were to conduct resistance evaluation of 112 Pakistani landraces and 48 advanced lines/ cultivars at seedling stage with total 10 virulent pathotypes of leaf rust, 3 from Pakistan and 7 from U.S.A and to detect closely linked markers for Lr10, 16, 34 and 67 genes through marker-assisted selection (MAS). Findings revealed most of Pakistani landraces showed lack of resistance at seedling stage. Only 7 accessions of landraces and 11 advanced lines were found highly resistant against all pathotypes of Pakistan. Similarly, 10 advanced lines exhibited high resistance while variability in resistance was recorded for landraces against all pathotypes tested from USA. Marker-assisted selection revealed Lr genes i.e. Lr10, Lr16, Lr34 and Lr67 were present at various frequencies. Highest frequency was observed for Lr34 followed by Lr16 Lr67 while lowest was recorded for Lr10. These genetic resources and lines identified effective against Pakistan and USA pathotypes are potential sources for improvement of leaf rust (LR) resistance and can be utilized as valuable material for breeding resistant wheat cultivars.

Characterization of wheat monogenic lines with known Sr genes and wheat cultivars for resistance to three new races of Puccinia graminis f. sp. tritici in China

Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a potentially devastating fungal disease of wheat worldwide. The present study was to evaluate the resistance of 42 wheat monogenic lines with known stem rust resistance (Sr) genes and 69 wheat cultivars to three new Pgt races (34C0MRGQM, 34C3MKGQM, and 34C6MTGSM) identified from aeciospores at the seedling and adult-plant stages. The phenotyping results revealed that monogenic lines harboring resistance genes Sr9e, Sr17, Sr21, Sr22, Sr26, Sr30, Sr31, Sr33, Sr35, Sr36, Sr37, Sr38, Sr47, SrTmp, and SrTt3 were effectively resistant to all three Pgt races at the seedling and adult-plant stages. In contrast, monogenic lines containing Sr5, Sr6, Sr7b, Sr9a, Sr9d, Sr9f, Sr9g, Sr9b, Sr16, Sr24, Sr28, and Sr39 were highly susceptible to these races at both seedling and adult-plant stages. The other lines with Sr8a, Sr10, Sr11, Sr13, Sr14, Sr15, Sr18, Sr20, Sr19, Sr23, Sr25, Sr27, Sr29, Sr32, and Sr34, displayed variable levels of resistance to one or two of the tested races. Seedling infection types (ITs) and adult-plant infection responses (IRs) indicated that 41 (59.4%) of the wheat cultivars showed high resistance to all the three races. Molecular marker analysis showed that four wheat culitvars likely carried Sr2, 20 wheat culitvars likely carried Sr31, 9 wheat culitvars likely carried Sr38, and none of the cultivars carried Sr24, Sr25, and Sr26. Our results provide a scientific basis for rational utilization of the tested Sr genes and wheat cultivars against these novel Pgt races.

Differential Responses to Yellow-Rust Stress Assist in the Identification of Candidate Wheat (Triticum aestivum L.) Genotypes for Resistance Breeding

Yellow rust (YR) globally affects wheat crops. It may turn into an epidemic, resulting in significant yield losses if the environment is suited to YR spread. The provision of resistant wheat cultivars is a sustainable protection strategy against YR. The current study aimed to use a combination of classical analytical tools to identify potential wheat lines through screening under YR stress for utilization in YR-resistance breeding. A total of 14 parents, which included 9 lines and 5 testers, were formed into 45 cross combinations via line × tester mating format. The tested germplasm was grown in a triplicate randomized full-block design, under optimal and yellow rust (YR)-stress conditions. Data were recorded on different morphological, physiochemical, yield and component traits at appropriate crop stages. A pre-combining ability analysis revealed significant inter-genotype variations. A combining ability study identified non-additive gene action in the inheritance of most of the investigated traits. Four potential parents (PR128, AN179, KS17 and WD17) and two crosses (PR128 × WD17 and AN179 × KS17) retained higher combining ability values for yield traits under YR-stress. A cluster analysis based on the overall performance found divergent classes among the screened genotypes. The clustering of different genotypes was shifted under YR-stress, which suggests variable genotypic response. Through factor analysis, we assessed and confirmed genotypes performing consistently under YR-stress. The identified genotypes may be used for disease-resistance breeding in wheat. Based on their positive correlation with grain yield, we suggest the use of peduncle length and tillers per plant as phenotypic markers for wheat selection and breeding. The knowledge base generated through the current study will add to the ongoing research on sustainable wheat breeding program.

Characterization of commercial common wheat cultivars for resistance to tan spot causative agent

Tan spot of wheat (pyrenophorosis) is a worldwide spread and economically significant disease of wheat. Growing resistant cultivars is an environmentally friendly method of disease control. The aim of the present work was to assess tan spot resistance in common wheat cultivars recommended for cultivation in the Russian Federation, and to identify the dominant Tsn1 allele using a molecular marker. The assessment involved 39 winter and 31 spring wheat cultivars included in the State Register of Selection Achievement in 2018-2020. Evaluation of wheat resistance was carried out in laboratory conditions under artificial inoculation of seedlings and leaf segments. Two isolates of Pyrenophora tritici-repentis (Died.) Drechs, producing ToxA toxin (I_ToxA) and ToxB toxin (ToxB) were used. The dominant allele of the Tsn1 gene was identified using the Xfcp623 marker. A high level of resistance (R) to both isolates (I_ToxA and I_ToxB) was shown by spring cultivars ‘Grenada’ and ‘Silach’; moderate resistance (MR) was demonstrated by winter cultivars ‘Felicia’ and ‘Akhmat’ and spring cultivars ‘Omskaya 42’, ‘Zauralskaya Zhemchuzhina’, ‘Radmira’, ‘Tarskaya 12’ and ‘Extra’. A resistant reaction (R, MR) to the isolate I_ToxA was typical for 26% of winter cultivars and 45% of spring ones. The number of cultivars resistant to the I_ToxB isolate was significantly higher (59% and 52%, respectively). The total fraction of cultivars resistant to the isolate I_ToxA (reaction R, MR) in the collection of winter wheat was 26% and 45% in the spring wheat collection; while the fractions of cultivars resistant to the I_ToxB isolate in these collections were equal to 59% and 52%, respectively. By using the Xfcp623 marker, the diagnostic product was amplified in winter cultivars ‘Bodry’, ‘Kavalerka’, ‘Timiryazevka 150’, ‘Shef’, ‘Anastasia’, ‘Barynya’, ‘Donskaya Step’, ‘Elanskaya’ and spring cultivars ‘Odeta’, ‘Stolypinskaya 2’, ‘Iren’ 2’ and ‘OMGAU 100’. All these cultivars were moderately susceptible to the isolate I_ToxA, with the exception of ‘Odeta’ and ‘Iren’ 2’, which may indicate a decrease in the expression level of the ToxA gene in genotypes of these cultivars.

Breeding Tools for Assessing and Improving Resistance and Limiting Mycotoxin Production by Fusarium graminearum in Wheat

The recently adopted conservation and minimum tillage practices in wheat-production systems coupled with the concomitant warming of the Earth are believed to have caused the upsurges in Fusarium head blight (FHB) prevalence in major wheat-producing regions of the world. Measures to counter this effect include breeding for resistance to both initial infection of wheat and spread of the disease. Cases of mycotoxicosis caused by ingestion of wheat by-products contaminated with FHB mycotoxins have necessitated the need for resistant wheat cultivars that can limit mycotoxin production by the dominant causal pathogen, Fusarium graminearum. This manuscript reviews breeding tools for assessing and improving resistance as well as limiting mycotoxin contamination in wheat to reflect on the current state of affairs. Combining these aspects in wheat research and development promotes sustainable quality grain production and safeguards human and livestock health from mycotoxicosis.

Wheat transcriptomic responses to extended feeding by wheat curl mites

The economic importance of wheat and its contribution to human and livestock diets has been already demonstrated. However, wheat production is impacted by pests that induce yield reductions. Among these pests, wheat curl mite (WCM, Aceria tosichella Keifer) impacts wheat all around the world. WCM are tiny pests that feed within the whorl of developing leaves, and their feeding causes leaf curling by preventing them from unfurling. The curling of the leaves provides a protective niche for the WCM. Additionally, WCM are also the vector of serious viruses in wheat. Little is known regarding the impact of the WCM on wheat transcriptome, and to date, only one article has been published describing the wheat transcriptomic changes after 1 day of WCM feeding. To better understand the wheat transcriptome variation after extended feeding by WCM [10 days post infestation (dpi)], we used an RNA-seq approach. We collected WCM-infested and uninfested leaves from two wheat cultivars: Byrd (WCM resistant) and Settler CL (WCM susceptible) at 10 dpi. Our transcriptomic analysis revealed the common and specific transcriptomic variations in WCM resistant and susceptible wheat cultivars, chromosome 3D specific location of the differentially expressed genes with functions involved in defense and stress response, and also identified the gene functions related to lipid signaling and membrane integrity, and phytohormone pathways potentially contributing to WCM resistance. Collectively, our study provides important insights on wheat defense mechanisms against WCM after extended feeding.

The Black Necrotic Lesion Enhanced Fusarium graminearum Resistance in Wheat.

Fusarium head blight, mainly incited by Fusarium graminearum, is a devastating wheat disease worldwide. Diverse Fusarium head blight (FHB) resistant sources have been reported, but the resistance mechanisms of these sources remain to be investigated. FHB-resistant wheat germplasm often shows black necrotic lesions (BNLs) around the infection sites. To determine the relationship between BNL and FHB resistance, leaf tissue of a resistant wheat cultivar Sumai 3 was inoculated with four different F. graminearum isolates. Integrated metabolomic and transcriptomic analyses of the inoculated samples suggested that the phytohormone signaling, phenolamine, and flavonoid metabolic pathways played important roles in BNL formation that restricted F. graminearum extension. Exogenous application of flavonoid metabolites on wheat detached leaves revealed the possible contribution of flavonoids to BNL formation. Exogenous treatment of either salicylic acid (SA) or methyl jasmonate (MeJA) on wheat spikes significantly reduced the FHB severity. However, exogenous MeJA treatment prevented the BNL formation on the detached leaves of FHB-resistant wheat Sumai 3. SA signaling pathway influenced reactive oxygen species (ROS) burst to enhance BNL formation to reduce FHB severity. Three key genes in SA biosynthesis and signal transduction pathway, TaICS1, TaNPR1, and TaNPR3, positively regulated FHB resistance in wheat. A complex temporal interaction that contributed to wheat FHB resistance was detected between the SA and JA signaling pathways. Knowledge of BNLs extends our understanding of the molecular mechanisms of FHB resistance in wheat and will benefit the genetic improvement of wheat FHB resistance.

Biogenic VOCs Emission Profiles Associated with Plant-Pest Interaction for Phenotyping Applications.

Pest attacks on plants can substantially change plants’ volatile organic compounds (VOCs) emission profiles. Comparison of VOC emission profiles between non-infected/non-infested and infected/infested plants, as well as resistant and susceptible plant cultivars, may provide cues for a deeper understanding of plant-pest interactions and associated resistance. Furthermore, the identification of biomarkers—specific biogenic VOCs—associated with the resistance can serve as a non-destructive and rapid tool for phenotyping applications. This research aims to compare the VOCs emission profiles under diverse conditions to identify constitutive (also referred to as green VOCs) and induced (resulting from biotic/abiotic stress) VOCs released in potatoes and wheat. In the first study, wild potato Solanum bulbocastanum (accession# 22; SB22) was inoculated with Meloidogyne chitwoodi race 1 (Mc1), and Mc1 pathotype Roza (SB22 is resistant to Mc1 and susceptible to pathotype Roza), and VOCs emission profiles were collected using gas chromatography-flame ionization detection (GC-FID) at different time points. Similarly, in the second study, the VOCs emission profiles of resistant (‘Hollis’) and susceptible (‘Alturas’) wheat cultivars infested with Hessian fly insects were evaluated using the GC-FID system. In both studies, in addition to variable plant responses (susceptibility to pests), control treatments (non-inoculated or non-infested) were used to compare the VOCs emission profiles resulting from differences in stress conditions. The common VOC peaks (constitutive VOCs) between control and infected/infested samples, and unique VOC peaks (induced VOCs) presented only in infected/infested samples were analyzed. In the potato-nematode study, the highest unique peak was found two days after inoculation (DAI) for SB22 inoculated with Mc1 (resistance response). The most common VOC peaks in SB22 inoculated with both Mc1 and Roza were found at 5 and 10 DAI. In the wheat-insect study, only the Hollis showed unique VOC peaks. Interestingly, both cultivars released the same common VOCs between control and infected samples, with only a difference in VOC average peak intensity at 22.4 min retention time where the average intensity was 4.3 times higher in the infested samples of Hollis than infested samples of Alturas. These studies demonstrate the potential of plant VOCs to serve as a rapid phenotyping tool to assess resistance levels in different crops.

Effects of irrigation on stem lignin and breaking strength of winter wheat with different planting densities

Increasing planting density is an important cultivation approach to improve wheat single yield. In field production, over irrigation under densified population conditions can easily cause lodging. Therefore, the lodging resistant wheat cultivar JM22 and the lodging sensitive wheat cultivar SN16 was used as experimental materials. Two irrigation treatments [rain-fed and spring irrigation (at jointing and anthesis stage)] were set with five planting densities (150 × 104 plants ha−1, 225 × 104 plants ha−1, 300 × 104 plants ha−1, 375 × 104 plants ha−1 and 450 × 104 plants ha−1). Lignin accumulation and its monomers (guaiacyl, syringyl and p-hydroxyphenyl) in combination with the apparent and microanatomic characteristics of the basal second stems, were determined to elucidate effects of irrigation on the formation of breaking strength in wheat stems at different planting densities. The results showed that the most important factors affecting the breaking strength of stems were different in different stages and different treatments. Through multiple stepwise regression analysis, it was found that under low density (150 × 104 plants ha−1) conditions, irrigation decreased breaking strength of stem mainly by affecting lignin accumulation and its subunits. However, at medium and high density (225 × 104 plants ha−1-375 × 104 plants ha−1), the decrease of stem breaking strength caused by irrigation was the result of the co-regulation of lignin metabolism, stem microscopic and morphological characteristics. At anthesis stage, when irrigated under the condition of low density (150 × 104 plants ha−1), the content of G subunit increased by 100 μg g−1, the stem breaking strength increased by 0.4 N. At medium density (225 × 104 plants ha−1-300 × 104 plants ha−1), irrigation increased S subunit content by 100 μg g−1, which resulting in high stem breaking strength by 0.5 N. However, at high density (375 × 104 plants ha−1-450 × 104 plants ha−1), along with H subunit content was increased by 10 μg g−1, the stem breaking strength was decreased by 0.14 N. Under irrigated and densified populations conditions, the decreasing range of wall thickness (−13.53%), stem filling degree (−16.65%) and the increasing range of H monomer ratio (15.77%) of high lodging resistance varieties were lower than those of SN16. Therefore, it held better ability to resist adverse environment and maintain lodging resistance. In this experiment, on the basis of irrigation (at jointing and anthesis stage) and 25 × 104 plants ha−1 planting density resulted in the highest yield (10,325.03 kg ha−1) and moderate stem.

TaPR1 Interacts With TaTLP1 via the αIV Helix to Be Involved in Wheat Defense to Puccinia triticina Through the CAPE1 Motif.

Pathogenesis-related (PR) proteins play important roles in plant defense response and systemic acquired resistance (SAR). PR1 has antifungal activity against many plant pathogens. In our previous study, RNA sequencing (RNA-seq) was conducted on resistant wheat line TcLr19 and sensitive wheat cultivar Chinese Spring inoculated with Puccinia triticina (Pt) race PHNT. In this study, seven salicylic acid (SA)-induced TaPR1 genes involved in plant disease resistance were found in the RNA-seq library. Quantitative PCR (qPCR) results showed that TaPR1-4 was most induced by Pt among these seven TaPR1 genes in the incompatible interaction. Yeast two-hybrid (Y2H) results showed that TaPR1-4 interacted with TaTLP1 via the αIV helix. Protein-mediated phenotyping assays in vivo and antifungal activity in vitro demonstrated that wheat leaves infiltrated with pure TaPR1-4 protein developed significantly less disease compared to control leaves. This effect was correlated with a strong increase in defense gene expression, and resistance activity was dependent on the CAPE1 motif located in the C-terminal region of TaPR1-4. These findings increase current knowledge regarding the interaction of TaPR1 and TaTLP1 and provide new insights on the role of TaPR1 protein in the resistance of wheat to Pt.

Evaluation of Kenyan wheat (Triticum aestivum L.) cultivars for rust resistance, yield and yield components

Stem rust (Puccinia graminis f. sp. tritici) is an important fungal disease of wheat (Triticum aestivum) due to its ability to cause severe yield losses on susceptible cultivars grown under conducive conditions. The objective of this study was to evaluate 81 Kenyan wheat cultivars for yield, agronomic traits and resistance to rust. A 3-season field experiment was conducted in a 9 × 9 partially balanced lattice design at KALRO, Njoro (0˚ 20’S and 35˚ 56’E) under stem rust (Sr) and yellow rust (Yr) pressure. The results from this study showed that effects due to season, cultivar and cultivar × season interaction were significant (p≤0.001) for number of kernels spike-1, Area Under Disease Progress Curve for stem rust (AUDPC_SR), Area Under Disease Progress Curve for yellow rust (AUDPC_YR), yield, 1000-kernel weight (TKW), biomass and days to heading. Principal component analysis showed AUDPC was the most effective disease parameter for determining rust resistance and biplot analysis identified cultivars K. Fahari, K. Kingbird, K. Songbird and K. Pelican with desirable traits for yield, TKW, biomass and kernels spike -1. Stem rust contributed to the highest in reduction of yield and TKW accounting for 12.87% and 21.95% variation, respectively while Yr contributed the most to biomass reduction accounting for 25.65% variation. From this study, cultivars Bounty, Lenana, and K. Leopard which produced high yield, low AUDPC_SR and AUDPC_YR values ranging from 3.5- 32.2 and 15.6-80.4, respectively can be used as valuable genetic stocks for improvement of rust resistance in wheat cultivars in Kenya

QTL mapping for adult plant field resistance to stripe rust in the AAC Cameron/P2711 spring wheat population

AbstractStripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease of wheat (Triticum aestivum L.). Deployment of resistant wheat cultivars is one of the best strategies to mitigate disease‐associated risks. The genotype P2711 possesses effective stripe rust resistance under field conditions in western Canada, however, the genetic basis of this resistance is unknown. To identify resistance, a recombinant inbred line (RIL) population comprised of 252 RILs was developed from the cross AAC Cameron/P2711. This population was evaluated for stripe rust severity at the adult plant stage in Creston, BC (in 2018, 2019, and 2020) and Lethbridge, AB (in 2018 and 2020), and was genotyped using the wheat 90K iSelect single nucleotide polymorphism (SNP) assay. A high‐density genetic map comprised of 8,915 markers was constructed covering all the wheat chromosomes. Four resistance quantitative trait loci (QTLs) were contributed by P2711 and three from AAC Cameron. QYr.lrdc‐2A.1, corresponding to the Yr17 gene, was the most stable QTL and detected in four out of five environments, whereas QYr.lrdc‐2B was the second most stable QTL. These two QTL along with QYr.lrdc‐5A showed a significant reduction in stripe rust severity when present together. Where most of the QTLs detected in both locations, QYr.lrdc‐1A.1 and QYr.lrdc‐1A.2, both were detected only in Creston, BC. Stable QTLs on chromosome 2A, 2B, and 5A, and their closely associated markers identified in this study could be utilized in marker‐assisted selection for stripe rust resistant cultivar development.

Yield Losses Associated with Different Levels of Stripe Rust Resistance of Commercial Wheat Cultivars in China.

Wheat stripe rust is one of the most destructive diseases to affect wheat. Although the major resistant wheat varieties have made a great contribution to global food security, yield losses from stripe rust still occur in large wheat growing areas when climatic conditions are unstable. Despite this threat, resistance levels and yield losses of these elite wheat cultivars under wheat stripe rust infection have not been well studied. Based on this investigation of natural infection conditions over 2 years, analysis of the area-under-the-disease-progress-curves differentiated the susceptible cultivars Mianmai 367 (MM367; 788.59), Jinmai 47 (JM47; 1,087.71), and Avocet Susceptible (AvS; 1,314.59) from resistant cultivars Xikemai 18 (XKM18; 177.50) and Xiaoyan 6 (XY6; 545.67). Stripe rust resulted in a 2-year mean yield loss of 32% for all tested varieties. The susceptible varieties JM47, AvS, and MM367 lost 64, 55, and 21% of grain yield, respectively. On the contrary, rust-resistant cultivars XKM18 and XY6 lost only 11 and 28%, respectively. In addition, stripe rust resulted in reduced kernel hardness, flour yield, and flour whiteness. Dough and gluten properties were also affected. Overall, results revealed that the grain yield and quality loss values of the resistant wheat cultivars were less than in the susceptible cultivars. Disease-resistant cultivars such as XKM18 should be promoted and recommended for application. It may also be suggested that growing a susceptible variety such as MM367 could be feasible in combination with fungicide application under high disease pressure.

Screening and Evaluation for Antixenosis Resistance in Wheat Accessions and Varieties to Grain Aphid, Sitobion miscanthi (Takahashi) (Hemiptera: Aphididae).

The grain aphid, Sitobion miscanthi causes serious damage by removing nutritional content from wheat plants and transmitting viral diseases. The use of resistant wheat cultivars is an effective method of aphid management. To identify S. miscanthi resistant cultivars, preliminary antixenosis resistance screening was conducted on 112 Ethiopian and 21 Chinese wheat accessions and varieties along with bioassay to test for further antixenosis resistance, identification of aphid feeding behavior using electrical penetration graph (EPG), and imaging of leaf trichome densities using a 3D microscope. According to antixenosis resistance screening, one highly-resistant, 25 moderately-resistant, and 38 slightly-resistant wheat cultivars to S. miscanthi were identified. Aphid choice tests showed that Luxuan266, 243726, and 213312 were the least preferred after 12, 24, 48, and 72 h of S. miscanthi release. Longer duration of Np, longer time to first probe, and shorter duration of E2 waveforms were recorded in Lunxuan266, 243726, and 213312 than in Beijing 837. The trichome density on adaxial and abaxial leaf surfaces of Lunxuan266, 243726 and 213312 was significantly higher than on those of Beijing 837. We concluded that Lunxuan266, 243726, and 213312 were antixenosis resistant to S. miscanthi based on the choice test, EPG results, and leaf trichome densities.

Registration of ‘Faraj’, a Hessian fly– and multiple disease–resistant durum wheat cultivar in Morocco

AbstractDurum wheat [Triticum turgidum L. ssp. durum (Desf.)] is cultivated on nearly one million hectares in Morocco.About half of the durum‐planted areas are located in unfavorable rainfed areas. The predominant abiotic stresses are drought and heat, and the predominant biotic stresses are Hessian fly, leaf rust, tan spot, Septoria blotch, and root rot. End use grain quality‐related traits are important. ‘Faraj’ (Reg. no. CV‐1190, PI 699898) is a durum cultivar that possesses adaptation to drought and genetic resistance to Hessian fly, leaf rust, tan spot, and Septoria leaf blotch and tolerance to root rot. Faraj possesses good levels of grain yellow pigment and grain protein concentration. Faraj was registered in 2007 and released to seed commercialization in 2014. Faraj could be used by breeders as a good genetic resource with grain yield potential and end use quality as well as resistance or tolerance to multiple diseases and pests.

Identification of Secreted Protein Gene-Based SNP Markers Associated with Virulence Phenotypes of Puccinia striiformis f. sp. tritici, the Wheat Stripe Rust Pathogen.

Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) is a destructive disease that occurs throughout the major wheat-growing regions of the world. This pathogen is highly variable due to the capacity of virulent races to undergo rapid changes in order to circumvent resistance in wheat cultivars and genotypes and to adapt to different environments. Intensive efforts have been made to study the genetics of wheat resistance to this disease; however, no known avirulence genes have been molecularly identified in Pst so far. To identify molecular markers for avirulence genes, a Pst panel of 157 selected isolates representing 126 races with diverse virulence spectra was genotyped using 209 secreted protein gene-based single nucleotide polymorphism (SP-SNP) markers via association analysis. Nineteen SP-SNP markers were identified for significant associations with 12 avirulence genes: AvYr1, AvYr6, AvYr7, AvYr9, AvYr10, AvYr24, AvYr27, AvYr32, AvYr43, AvYr44, AvYrSP, and AvYr76. Some SP-SNPs were associated with two or more avirulence genes. These results further confirmed that association analysis in combination with SP-SNP markers is a powerful tool for identifying markers for avirulence genes. This study provides genomic resources for further studies on the cloning of avirulence genes, understanding the mechanisms of host–pathogen interactions, and developing functional markers for tagging specific virulence genes and race groups.

Genetic mapping of powdery mildew resistance genes in wheat landrace Guizi 1 via genotyping by sequencing.

Wheat (Triticum aestivum L.) powdery mildew (Pm), which caused by Blumeria graminis f. sp. tritici (Bgt), is a destructive disease worldwide that causes severe yield losses in wheat. Resistant wheat cultivars easily lose their ability to effectively resist newly emerged Bgt strains; therefore, identifying new resistance genes is necessary for breeding resistant cultivars. Guizi 1 (GZ1) is a Chinese wheat cultivar with moderate and stable resistance to Pm. Genetic analysis indicated that the Pm resistance of GZ1 was controlled by a single dominant gene, designated PmGZ1. In total, 110 F2 individual plants and their 2 parents were subjected to genotyping by sequencing (GBS), which yielded 23,134 high-quality single-nucleotide polymorphisms (SNPs). The SNP distributions across the 21 chromosomes ranged from 134 on chromosome 6D to 6288 on chromosome 3B. Chromosome 6A has 1866 SNPs, among which 16 are physically located between positions 307,802,221 and 309,885,836 in an approximate 2.3-cM region; this region also had the greatest SNP density. The average map distance between SNP markers was 0.1cM. A quantitative trait locus (QTL) with a significant epistatic effect on Pm resistance was mapped to chromosome 6A. The logarithm of odds (LOD) value of PmGZ1 was 34.8, and PmGZ1 was located within the confidence interval marked by chr6a-307802221 and chr6a-309885836. Moreover, 74.7% of the phenotypic variance was explained by PmGZ1. Four candidate genes (which encoded two TaAP2-A and two actin proteins) were annotated maybe as resistance genes. The present results provide valuable information for wheat genetic improvement, QTL fine mapping, and candidate gene validation.

Introgression of pre-harvest sprouting resistance from hexaploid wheat into high yielding durum wheat germplasm

Pre-harvest sprouting (PHS) is a critical factor affecting wheat producing regions characterized by rainfall and high humidity combined with cool temperatures at harvest. This phenomenon is particularly important in durum wheat (Triticum durum L.), which is generally susceptible to PHS, in contrast to common wheat (Triticum aestivum L.) which expresses better resistance. The transfer of PHS from hexaploid common wheat into tetraploid durum wheat germplasm is one option for genetic improvement, because the two species share two related sub-genomes. In the present study, through interspecific hybridization and modified backcross approaches, we developed experimental durum lines that showed greater PHS resistance than the recurrent durum wheat parent, with some expressing better PHS performance than the resistant common wheat donor. The introgression of PHS resistance did not negatively impact additional traits in the durum background and several backcross derived experimental lines expressed superior grain yield related and quality traits when compared with the recurrent parent. These lines represent a promising genetic resource for the development of new sprouting resistant durum wheat cultivars. Our results demonstrate that PHS resistance can be transferred from common wheat to improve PHS of durum wheat germplasm.

Cereal and Pulse Crops with Improved Resistance to Pratylenchus thornei Are Needed to Maximize Wheat Production and Expand Crop Sequence Options

In the subtropical grain region of eastern Australia, two experiments were conducted, one initially with 2490 P. thornei/kg soil, the other with 8150 P. thornei/kg soil at 0–0.9 m soil depth. We determined the effect of P. thornei, residual from a weed-free fallow and pre-cropping with several cultivars each of barley (Hordeum vulgare), faba bean (Vicia faba), chickpea (Cicer arietinum), and wheat (Triticum aestivum) (Phase 1), on the growth of wheat cultivars with intolerance or tolerance to P. thornei (Phase 2). Pratylenchus thornei substantially increased after growing all cultivars of the Phase 1 faba bean, barley, and most cultivars of chickpea and wheat, and decreased after two moderately resistant wheat cultivars and the fallow treatment. The biomass of the Phase 2 tolerant cultivar ranged from 5070 to 6780 kg/ha and the intolerant cultivar 1020 to 4740 kg/ha. There was a negative linear relationship between P. thornei population densities and biomass of the Phase 2 intolerant cultivar but not of the tolerant cultivar. Growers are at risk of financial loss because they are restricted in their choice of crops to reduce damaging population densities of P. thornei. The development of resistant and tolerant crop genotypes can maximize production in P. thornei-affected farming systems.