Resistant Wheat Lines Research Articles

The effect of quantitative wheat resistance on the aggressiveness of Fusarium graminearum.

Little is known about the selection pressures acting on plant pathogen populations, especially those applied by quantitative forms of resistance. Fusarium graminearum causes Fusarium Head Blight (FHB) in wheat, producing significant yield losses and mycotoxin contamination. Quantitative host resistance is the best method to control FHB. However, there needs to be more understanding of how disease resistance affects the evolution of plant pathogens. This study aimed to determine if the presence or absence of wheat resistance influenced the fitness components and genomic regions of F. graminearum. Thirty-one isolates from highly susceptible and 25 isolates from moderately resistant wheat lines were used. Isolate aggressiveness was measured by area under the disease progress curve (AUDPC), visually damaged kernels, and deoxynivalenol contamination. In vitro growth rate and spore production were also measured. Two whole-genome scans for selection were conducted with 333,297 SNPs. One scan looked for signatures of selection in the entire sample and the other scan was for divergent selection between the isolates from moderately resistant wheat and highly susceptible wheat. The population of isolates from highly susceptible wheat was primarily aggressive. Several regions of the F. graminearum genome with signatures for selection were identified. The moderately resistant wheat varieties used in this study did not select more aggressive isolates, suggesting that quantitative resistance is a durable method to control FHB.

Morphological and Molecular Characterization of Locally Developed and Imported Dicoccum Wheat (Triticum Dicoccum (Schrank.) Schubl.) Germplasm Lines for Bipolaris Sorokiniana, Spot Blotch Disease Resistance

The importance of genetic resources lies in their pivotal role in improving the quality of crop varieties, particularly in enhancing their resilience to both biological and environmental stresses. One such challenge is Spot blotch (SB), a destructive leaf disease that primarily affects wheat, especially in warm and humid regions, particularly the eastern parts of South Asia, including the eastern Gangetic plains and the Peninsular zone. Developing wheat cultivars with resistance to SB stands out as the most effective strategy for managing this disease. Therefore, the primary objective of the current study was to validate the resistance to SB in one hundred twenty-seven, dicoccum wheat germplasm accessions. This validation process relied on both observable traits and genetic characteristics. The germplasm accessions were obtained from various sources, including the International Center for Agricultural Research in the Dry Areas in Lebanon, the International Maize and Wheat Improvement Center in Mexico, and the International Maize and Wheat Improvement Center (CIMMYT) in Mexico. The evaluation for Spot blotch resistance was conducted in the field under controlled conditions of disease prevalence during the years 2020–21 and 2021–22. The assessment involved two vulnerable control cultivars (DDK-1025 and Sonalika) and two confirmed resistant control cultivars (Chirya-3 and HI-8663). Out of the 127 germplasm accessions tested, forty displayed resistance to SB, confirmed through a specific genetic marker known as Xgwm120. Notably, four accessions – Acc. GPM Dicoccom-IR-76, Acc. GPM Dicoccom-IR-98, Acc. GPM Dicoccom-IR-102, and ICARDA-14-127687 – exhibited even greater resistance than the well-established Spot blotch-resistant genotype, Chirya-3. These promising lines with resistance potential offer significant prospects for wheat breeders dedicated to developing spot blotch resistant wheat lines.

Analysis of resistance to stem rust and identification of <i>Sr</i> genes in introgressive lines of spring bread wheat

Background. Due to the increase in the harmfulness of wheat stem rust (Puccinia graminis f. sp. tritici Erikss. & E. Henn.) in the Volga region, and the likelihood of the spread of the aggressive Ug99 race, an assessment of the genetic diversity of wheat breeding lines and identification of effective Sr genes are of fundamental importance.Materials and methods. Ninety spring bread wheat introgressive lines with stem rust resistance, developed at the Federal Center of Agriculture Research of the South-East Region, were analyzed. Molecular markers were used to identify resistance genes: Sr24/Lr24, Sr25/Lr19, Sr26, Sr28, Sr31/Lr26, Sr32, Sr36, Sr38/Lr37, Sr39 and Sr57/Lr34. The analysis of plants for resistance was carried out according to standard methods; the Stakman scale was applied to determine the type of reaction.Results. The genes Sr31/Lr26, Sr25/Lr19, Sr57/Lr34, Sr38/Lr37 and Sr39/Lr35 were identified in the analyzed breeding lines. Sr25 was found in 51 lines (56,7% of samples), Sr31 in 41 lines (45.6%), Sr57/Lr34 in 5 lines, Sr38 in 10 lines and Sr39 in one line. Combinations of resistance genes were identified: Sr31+Sr25 in 28 lines (31.1%), Sr25+Sr38 in 5 lines, and Sr25+Sr39 in one line. The Sr24/Lr24, Sr26, Sr28, Sr32 and Sr36 genes were not identified.Conclusion. As a result, promising highly resistant introgressive wheat lines with promising combinations of Sr31+Sr25, Sr25+Sr38 and Sr25+Sr39 genes were identified. They can be used in Russian breeding programs for immunity.

Genome-wide identification and characterization of thaumatin-like protein family genes in wheat and analysis of their responses to Fusarium head blight infection

Thaumatin-like proteins (TLPs) play potential roles in plant resistance to various diseases. Identifying TLPs is necessary to determine their function and apply them to plant disease resistance. However, limited information is available about TLP-family genes in wheat, especially regarding their responses to Fusarium species, which cause Fusarium head blight in wheat. In this study, we conducted a comprehensive genome-wide survey of TLP genes in wheat and identified 129 TLP genes in the wheat genome, which were unevenly distributed on 21 wheat chromosomes, with 5A containing the highest number. Phylogenetic analysis showed that these 129 wheat TLP genes together with 24 Arabidopsis TLPs were classified into 7 groups based on the protein sequences. We systematically analyzed the genes in terms of their sequence characterization, chromosomal locations, exon–intron distribution, duplication (tandem and segmental) events and expression profiles in response to Fusarium infection. Furthermore, we analyzed differentially expressed TLP genes based on publicly available RNA-seq data obtained from a resistant near isogenic wheat line at different time points after Fusarium graminearum inoculation. Then, the expression of 9 differentially expressed TLP genes was confirmed by real-time PCR, and these 9 genes were all upregulated in the resistant Sumai 3 variety, which was generally consistent with the RNA-seq data. Our results provide a basis for selecting candidate wheat TLP genes for further studies to determine the biological functions of the TLP genes in wheat.Graphical

Automatic Tandem Dual BlendMask Networks for Severity Assessment of Wheat Fusarium Head Blight

Fusarium head blight (FHB) disease reduces wheat yield and quality. Breeding wheat varieties with resistance genes is an effective way to reduce the impact of this disease. This requires trained experts to assess the disease resistance of hundreds of wheat lines in the field. Manual evaluation methods are time-consuming and labor-intensive. The evaluation results are greatly affected by human factors. Traditional machine learning methods are only suitable for small-scale datasets. Intelligent and accurate assessment of FHB severity could significantly facilitate rapid screening of resistant lines. In this study, the automatic tandem dual BlendMask deep learning framework was used to simultaneously segment the wheat spikes and diseased areas to enable the rapid detection of the disease severity. The feature pyramid network (FPN), based on the ResNet-50 network, was used as the backbone of BlendMask for feature extraction. The model exhibited positive performance in the segmentation of wheat spikes with precision, recall, and MIoU (mean intersection over union) values of 85.36%, 75.58%, and 56.21%, respectively, and the segmentation of diseased areas with precision, recall, and MIoU values of 78.16%, 79.46%, and 55.34%, respectively. The final recognition accuracies of the model for wheat spikes and diseased areas were 85.56% and 99.32%, respectively. The disease severity was obtained from the ratio of the diseased area to the spike area. The average accuracy for FHB severity classification reached 91.80%, with the average F1-score of 92.22%. This study demonstrated the great advantage of a tandem dual BlendMask network in intelligent screening of resistant wheat lines.

Insights of auxin signaling F-box genes in wheat (Triticum aestivum L.) and their dynamic expression during the leaf rust infection.

The TRANSPORT INHIBITOR RESPONSE 1/AUXIN SIGNALING F-BOX (TIR1/AFB) protein serves as auxin receptor and links with Aux/IAA repressor protein leading to its degradation via SKP-Cullin-F box (SCFTIR1/AFB) complex in the auxin signaling pathway. Present study revealed 11 TIR1/AFB genes in wheat by genome-wide search using AFB HMM profile. Phylogenetic analysis clustered these genes in two classes. Several phytohormone, abiotic, and biotic stress responsive cis-elements were detected in promoter regions of TIR1/AFB genes. These genes were localized on homoeologous chromosome groups 2, 3, and 5 showing orthologous relation with other monocot plants. Most genes were interrupted by introns and the gene products were localized in cytoplasm, nucleus, and cell organelles. TaAFB3, TaAFB5, and TaAFB8 had nuclear localization signals. The evolutionary constraint suggested paralogous sister pairs and orthologous genes went through strong purifying selection process and are slowly evolving at protein level. Functional annotation revealed all TaAFB genes participated in auxin activated signaling pathway and SCF-mediated ubiquitination process. Furthermore, in silico expression study revealed their diverse expression profiles during various developmental stages in different tissues and organs as well as during biotic and abiotic stress. QRT-PCR based studies suggested distinct expression pattern of TIR1-1, TIR1-3, TaAFB1, TaAFB2, TaAFB3, TaAFB4, TaAFB5, TaAFB7, and TaAFB8 displaying maximum expression at 24 and 48h post inoculation in both susceptible and resistant near isogenic wheat lines infected with leaf rust pathogen. Importantly, this also reflects coordinated responses in expression patterns of wheat TIR1/AFB genes during progression stages of leaf rust infection.

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.

Rhizoctonia Resistance Is Negatively Correlated to Early Root Growth Rate in Synthetic Hexaploid Wheat Derivatives.

Resistance to the soilborne fungal pathogen Rhizoctonia solani AG-8 is desirable in adapted wheat and barley but remains an elusive trait for prebreeders and breeders. In a previous study, we observed that emergence and root growth was faster in the Rhizoctonia-susceptible 'Scarlet' than in its resistant counterpart, 'Scarlet-Rz1'. The objective of the current study was to quantify early root growth rate and total root length in resistant and susceptible synthetic hexaploid wheat lines, including parental lines and 22 recombinant inbred lines derived crosses between parental lines. In Petri dish assays, the susceptible lines displayed a faster rate of root growth during the first 40 h of root emergence compared with resistant lines. This growth differential was observed in 14-day and 48-h greenhouse assays, in which the total root length of susceptible parental lines was significantly (P < 0.05) greater than that of resistant parental lines. However, the resistant lines sustained less root loss compared with susceptible lines when R. solani AG-8 was present in the soil. Early root growth rate and total root length were not correlated to freezing tolerance in a set of wheat cultivars selected for cold tolerance. The findings indicated that early root growth was negatively correlated to R. solani AG-8 damage in resistant synthetic wheat lines developed for the Pacific Northwest, United States, and suggested that the dynamics of root emergence affect resistance to this soilborne pathogen.

Interaction effect of Root Lesion Nematodes and Fusarium culmorum Sacc. on disease complex in some wheat cultivars

The study was conducted to assess a possible interaction between fungal pathogen of Fusarium culmorum Sacc. and Root lesion nematodes at sequentially and simultaneously inoculation. Fusarium culmorum spore suspension effect evaluated on plant disease severity and nematode density on moderate resistant wheat line to F. culmorum (2-49) and susceptible wheat variety (İkizce) under controlled condition. The disease severity was higher on İkizce cv. than 2-49. This indicates that there is a considerable important pathogen resistance. Simultaneous and sequential inoculation of Pratylenchus thornei and F. culmorum reduced the final nematode density and reproduction rate more than inoculation with only nematode on İkizce cv. The simultaneously P. penetrans and F.culmorum inoculation (N+F) affected the positively of final density on İkizce cv. The N+ F treatment affected the positively of P. neglectus density on İkizce cv., whereas negative effect was found in pre or post inoculation of F. culmorum treatments. No synergistic interactions were detected on 2-49 when plants were co-infected by the root lesion nematode and fungus. It was determined that P. thornei had a positive effect on disease severity when it entered the plant simultaneously and before the F. culmorum on İkizce cv.. The disease severity decreased in F. culmorum was applied four weeks after the P. neglectus treatment on 2-49 wheat line and İkizce cv. In the interaction with F. culmorum on İkizce cv., differences were determined between the species of root lesion nematodes.

Screening of Some Ethiopian Wheat Lines Against Stem Rust Races at Seedling Stage

In Ethiopia, stem rust caused by Puccinia graminis f. sp. tritici (Pgt) is one of the most serious wheat diseases. On vulnerable cultivars, it has the ability to cause yield losses of up to 100%. The infection responses of forty-two wheat lines at the seedling stage against eleven isolates of stem rust race TTKSK (Ug99 race), TTRTF, TKTTF (Digalu race), JRCQC, TKKTF, TRTTF, TTTTF, TTKTF, TTKTT, RRTTF, and TKPTF were evaluated in a study. Wheat lines were experimentally infected with urediniospores of the races under controlled conditions at Ambo Plant Protection Research Center in 2021. Against the Pgt races that were examined, different seedling resistance responses were seen. Thirteen wheat lines, WL-1, WL-4, WL-21, WL-35, WL-37, WL-38, WL-41, WL-43, WL-45, WL-48, WL-49, WL-61, WL-64, had low infection types against all races, whereas six wheat lines, WL-26, WL-31, WL-33, WL-47, WL-51, and WL-66, had the resistant wheat lines discovered in this study can be exploited as a source of resistant genes for breeding program.

Comparative Transcriptome Analysis of Wheat Lines in the Field Reveals Multiple Essential Biochemical Pathways Suppressed by Obligate Pathogens.

Mildew and rust are the most devastating cereal pathogens, and in wheat they can cause up to 50% yield loss every year. Wheat lines containing resistance genes are used to effectively control fungal diseases, but the molecular mechanisms underlying the interaction between wheat and its fungal pathogens are poorly understood. Here, we used RNA sequencing (RNA-Seq) to compare the transcriptomic landscape of susceptible and resistant wheat lines to identify genes and pathways that are targeted by obligate biotrophic fungal pathogens. The five lines differed in the expression of thousands of genes under infection as well as control conditions. Generally, mixed infection with powdery mildew and leaf rust resulted in downregulation of numerous genes in susceptible lines. Interestingly, transcriptomic comparison between the nearly isogenic lines Thatcher and Thatcher-Lr34 identified 753 genes that are uniquely downregulated in the susceptible line upon infection. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, revealed the suppression of six major biochemical pathways, namely nuclear transport, alternative splicing, DNA damage response, ubiquitin-mediated proteolysis, phosphoinositol signaling, and photosynthesis. We conclude that powdery mildew and leaf rust evade the wheat defense system by suppression of programmed cell death (PCD) and responses to cellular damage. Considering the broad range of the induced changes, we propose that the pathogen targets “master regulators” at critical steps in the respective pathways. Identification of these wheat genes targeted by the pathogen could inspire new directions for future wheat breeding.

Advances in genetic studies of black point disease in wheat

Black point disease seriously affects wheat production around the world. Because the incidence of black point is influenced by both pathogens and the environments, selecting resistant wheat lines and then breeding resistant cultivars under natural field conditions are not reliable, and assessment of disease resistance through inoculation of pathogens under controlled environments is time-consuming and laborious. One effective method to develop wheat cultivars resistant to black point is through molecular marker-assisted selection (MAS). Wheat resistance against black point is determined by quantitative trait loci (QTL) with broad-sense heritabilities of black point incidence in a range of 0.52–0.78. One hundred and ten loci for black point resistance have been identified on all wheat chromosomes. Among them, homoeologous groups 2 and 5 chromosomes contain the most loci, with 21 and 19, respectively, and homoeologous group 6 chromosomes have the fewest loci (11). The A, B, and D genomes contain 34, 41, and 35 loci, respectively. Although many loci for black point resistance have been reported, the effects of major loci are not clear. Further, because of the lack of molecular markers and resistant germplasms screened by pathogen inoculation under controlled conditions, breeding wheat cultivars resistant to black point is still difficult. In this review, these major problems were examined, and suggestions on identifying pathogens and using accurate assessment technology are proposed. It will be conducive to develop molecular markers closely linked to major loci and create resistant germplasms through MAS, which will promote the progress in resistance breeding and the control of black point in wheat.

Evaluation of Stripe Rust (&lt;i&gt;Puccinia Striformis&lt;/i&gt; f. sp. &lt;i&gt;Tritici&lt;/i&gt;) Resistance in Bread Wheat (&lt;i&gt;Triticum&lt;/i&gt; &lt;i&gt;aestivum&lt;/i&gt; L.) Genotypes in Ethiopia

Adult Plant Resistance (APR) based on partial resistance is an important and effective way to combat yellow rust (Puccinia striiformis) in wheat production. The objective of current research was planned to evaluate the response of 436 wheat (Triticum aestivum) genotypes against yellow rust resistance under field conditions during 2020 main cropping season. Over locations, Partial resistance screening was evaluated through Final Rust Severity (FRS), Area under Disease Progress Curve (AUDPC), Coefficient of Infection (CI), Relative Area under Disease Progress Curve (rAUDPC) and field reaction have used for differentiating Adult plant resistances. Responses of four hundred thirty six genotypes, one hundred fourteen wheat lines were high adult plant resistance, fifty eight lines were found to be intermediate adult plant resistant and two hundred sixty four were low adult plant resistance over location. With rAUDPC values over location twenty seven were 1-10 shown resistant, eighty seven lines were 11-30 categorized as moderately susceptible and three hundred twenty two genotypes exhibited susceptible response against yellow rust with more than 31-100 rAUDPC value. High values above 31 prcent of rAUDPC showed greater severity of yellow rust on wheat genotypes while lower rAUDPC values indicated resistance to yellow rust. Fifty bread wheat genotypes that were selected based on overall agronomic performance (biomass, spike length, number of spikes/m2, tillering capacity, stalk strength or lodging resistance, shattering resistance and diseases resistance especially yellow rust and Septoria blotch. Three genotypes were EBW192345, EBW192346 and EBW192347 extraordinarily out performed evaluated materials phenotypically in terms of agronomic performance and diseases resistance over locations. The present study revealed that the lines were having enough diversity regarding slow rusting behavior and yellow rust resistance, ranging from immunity to partial resistant lines. Present research provided the resistant wheat lines to the breeders to incorporate in their breeding program against yellow rust.

Large-Scale Cloning and Comparative Analysis of TaNAC Genes in Response to Stripe Rust and Powdery Mildew in Wheat (Triticum aestivum L.).

The NAM, ATAF1/2, and CUC2 (NAC) transcription factors (TFs) constitute the largest plant-specific TF superfamily, and play important roles in various physiological processes, including stress responses. Stripe rust and powdery mildew are the most damaging of the fungal diseases that afflict wheat (Triticum aestivum L.). However, studies on Triticum aestivum NAC (TaNAC)s’ role in resistance to the two diseases are still limited, especially in an overall comparative analysis of TaNACs responding or not to fungal stress. In the present study, 186 TaNAC transcripts were obtained from the resistant hexaploid wheat line N9134 under fungal stress, and 180 new transcripts were submitted to GenBank. Statistical results show that 35.1% (54/154) of TaNAC genes responded to stripe rust and powdery mildew in the seedling stage. “Abnormal” coding transcripts of differentially expressed (DE)-TaNAC genes in wheat responding to fungal stress were found in a significantly higher proportion (24/117 vs. 8/69, p = 0.0098) than in non-DE-NACs. This hinted that the alternative splicing of TaNAC genes was active in transcriptional or post-transcriptional regulation during plant-pathogen interactions. Full-length NAC proteins were classified into nine groups via phylogenetic analysis. Multiple-sequence alignment revealed diversity in the C-terminal structural organization, but the differentially expressed gene (DEG)-encoding proteins enriched in Subgroups VI and VII were conserved, with WV[L/V]CR amino acid residues in Motif 7 following the NAM domain. Our data that showed TaNAC TFs responded to fungal disease, which was affected by expression levels and by the regulation of multifarious transcript variants. These data for TaNAC responses to stripe rust and/or powdery mildew and their numerous structural variants provide a good resource for NAC function–mechanism analysis in the context of biotic-stress tolerance in wheat.

Identification of two novel Hessian fly resistance genes H35 and H36 in a hard winter wheat line SD06165.

Two new Hessian fly resistance QTLs (H35 and H36) and tightly linked SNP markers were identified in a US hard winter wheat SD06165. Hessian fly (HF), Mayetiola destructor (Say), is one of the most destructive pests in wheat (Triticum aestivum L.) worldwide. Growing resistant cultivars is the most effective approach to minimize Hessian fly damage. To identify new quantitative trait loci (QTLs) for HF resistance, a recombinant inbred line population was developed by crossing HF resistant wheat line SD06165 to a susceptible line OK05312. The population was genotyped with 1709 single-nucleotide polymorphisms (SNPs) generated from genotyping-by-sequencing and phenotyped for HF resistance in greenhouses. Two novel QTLs for HF resistance were identified from SD06165. The major QTL, designated as H35, was closely linked to SNP marker SDOKSNP7679 on chromosome 3BS that explained 23.8% and 36.0% of the phenotypic variations; the minor QTL, designated as H36, was flanked by SNP markers SDOKSNP1618 and SDOKSNP8089 on chromosome 7AS and explained 8.5% and 13.1% of the phenotypic variation in the two experiments. Significant interaction was detected between the two QTLs. Seventeen SNPs that tightly link to H35 and eight SNPs that tightly link to H36 were converted to kompetitive allele specific polymerase chain reaction markers for selecting these QTLs in breeding programs.

Developing stripe rust resistant wheat (Triticum aestivum L.) lines with gene pyramiding strategy and marker-assisted selection

Stripe rust or yellow rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat (Triticum aestivum L.) worldwide. Growing resistant cultivars is the most effective approach to control the disease. There have been numerous reports on the resistance genes to stripe rust (Yr gene) in wheat, but just a few Yr genes are resistant to currently epidemic races and applied in wheat production. Gene pyramiding is considered to be an effective way to enhance durable disease resistance in crops. In this experiment, a panel of Yr gene pyramiding lines (consisting of 3–8 Yr genes) with cv. Chuanyu12 as background parent were constructed by using marker assistant selection and evaluated under currently epidemic Pst races. The results showed that the number of pyramided Yr genes was significant correlated with stripe rust resistance (p < 0.001). Yr15, Yr62 and Yr65 are effective to the current Pst races. Pyramiding more than four effective or partially effective Yr genes can provide enough resistance to stripe rust. And additive effects or epistatic effects existed in gene combinations in this study, such as Yr26 + Yr48, Yr30 + Yr64 and Yr30 + Yr48 et al. Moreover, the effects of Yr gene pyramids on currently prevalent Pst races and agronomic traits were also evaluated, and Yr-gene pyramiding lines with desirable agronomic traits were obtained for durable controlling Pst in wheat breeding.

Large-scale stage-specific regulation of gene expression during host-pathogen interactions in CSP44 bread wheat carrying APR gene Lr48.

Genome-wide transcriptome analysis was undertaken in a leaf-rust resistant bread wheat line CSP44 (selected from Australian cv. Condor) carrying the adult plant resistance (APR) gene Lr48. Two pre-adult plant (P-AP) susceptible stages (S48 and S96) and two adult plant (AP) resistant stages (R48 and R96) were used for RNA-seq. At the susceptible P-AP stage (during S48 to S96), expression increased in 2062 genes, and declined in 130 genes; 1775 of 2062 differentially expressed genes (DEGs) also exhibited high expression during early incompatible stage R48. Comparison of S96 with R96 showed that the expression of 80 genes was enhanced and that of 208 genes declined at the AP stage. At the resistant AP stage (during R48 to R96), expression of mere 25 genes increased and that of 126 genes declined. Apparently, the resistance during late adult stage (R96) is caused by regulation of the expression of relatively fewer genes, although at pre-adult stage (S48 to S96), expression of large number of genes increased; expression of majority of these genes kept on increasing during adult stage at R48 also. These and other results of the present study suggest that APR may mimic some kind of systemic acquired resistance (SAR). The host-specific DEGs belonged to 10 different classes including genes involved in defence, transport, epigenetics, photosynthesis, genes encoding some transcription factors etc. The pathogen (Puccinia triticina) specific DEGs (including three genes encoding known biotrophic effectors) seem to help the pathogen in infection/growth through large-scale stage-specific enhanced expression of host's genes. A putative candidate gene for Lr48 containing protein kinase domain (its ortholog in rice encoding OsWAK8) was also identified.

ВПЛИВ ФІТОПАТОГЕННИХ БАКТЕРІЙ ТА ІХНІХ ЛІПОПОЛІСАХАРИДІВ НА КАЛЮСНІ КЛІТИНИ ПШЕНИЦІ

It was shown the effect of inactivated cells and lipopolysaccharide of the causative agent of basal bacteriosis of wheat Pseudomonas syringae pv. atrofaciens on the proliferation of wheat callus cells. It was established that inactivated cells and LPS of P. syringae pv. atrofaciens in doses of 0,4 % and 0,5 % showed physiological activity in reducing cell viability in callus culture by 89,5 - 93,6 % and increasing the activity of peroxidase. It was shown the possibility of using LPS as a selective factor for the selection of resistant wheat lines. Keywords: callus cells, wheat, Pseudomonas syringae pv. а trofaciens .

Response of wheat genotypes against leaf rust (Puccinia triticina) under field conditions

Leaf rust occurs worldwide wherever wheat is grown. The current research was planned to evaluate the response of 37 wheat (Triticum aestivum) genotypes against leaf rust resistance under field conditions during crop season 2017-18.These genotypes were sown in augmented design with two meter long line sowing method with 30 cm row to row distance at research area of Agricultural Biotechnology Research Institute (ABRI), Ayub Agricultural Research Institute (AARI), Faisalabad, Pakistan. After every five genotypes, a line of rust spreader “Morocco” was sown. Moreover, the trial was also surrounded by planting two rows of spreader to increase the inoculum pressure. Data was recorded on the basis of leaf rust severity scale. Leaf rust severity response was variable among tested genotypes. Out of thirty-seven genotypes, five wheat lines were immune (no disease symptoms) i.e. 17BT007, 17BT013, 16BT008, 16BT010 and 16BT011. Seven lines were found to be resistant with AUDPC vales ranged 1-199. Response of ten lines was moderately resistant while five lines were categorized as moderately susceptible. Ten genotypes exhibited susceptible response against leaf rust with more than 600 AUDPC value. High values above 600 of AUDPC showed greater incidence of leaf rust on wheat plants while lower AUDPC values indicated resistance to leaf rust. Present research provided the resistant wheat lines to the breeders to incorporate them in their breeding program against leaf rust.

A Novel QTL in Durum Wheat for Resistance to the Wheat Stem Sawfly Associated with Early Expression of Stem Solidness.

The wheat stem sawfly (WSS) (Cephus cinctus Norton) is a major yield-reducing pest of wheat (Triticum aestivum L.). Varieties with pith-filled, or solid, stems provide a measure of resistance by inhibiting larval survival inside the stem. Durum wheat (Triticum turgidum L.) has resistance to the wheat stem sawfly even in the absence of known genes for stem solidness. To determine the genetic basis of resistance in durum wheat, a susceptible durum wheat, PI 41353, was identified from among 1,211 landrace accessions from around the world screened in WSS-infested sites. A recombinant inbred line (RIL) population of 105 individuals was developed from a cross of PI 41353 with a typically resistant variety, Pierce. The RIL were screened in a total of three WSS-infested locations in Montana over a two year period. A genetic map was constructed with 2,867 SNP-based markers. A quantitative trait locus (QTL) analysis identified six QTL associated with resistance. An allele from resistant cultivar Pierce at a QTL on chromosome 3A, Qss.msub-3AL, caused a 25% reduction in stem cutting. Assessment of near-isogenic lines that varied for alleles at Qss.msub-3AL showed that the Pierce allele was also associated with higher stem solidness as measured early in stem development, which is a critical stage for WSS oviposition and larval development. Stem solidness of Pierce and other resistant durum wheat lines largely disappeared later in plant development. Results suggest a genetic mechanism for WSS resistance observed in durum wheat, and provide an additional source of WSS resistance for hexaploid bread wheat.