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Blumeria graminis (DC). E.U. Speer f.sp. tritici Em. Marchal (Syn. Erysiphe graminis DC f.sp. tritici, Em. Marchal), a causal organism of powdery mildew (PM), is one of the important diseases of wheat worldwide. A comprehensive evaluation of wheat germplasm accessions (19,460) conserved in the National Genebank of ICAR–National Bureau of Plant Genetic Resources was conducted to identify sources of resistance to PM. Accessions belonging to the three wheat species—bread wheat (Triticum aestivum L. subsp. aestivum) (15,944), durum wheat (T. durum Desf.) (3,359), and emmer wheat (T. dicoccum Schrank ex Schübl.) (157)—were screened at Wellington, a hotspot location for PM, for two consecutive seasons. Screening results indicated that 7271 (45%) from bread wheat, 756 (22%) from durum wheat, and 22 (14%) from emmer were resistant. Out of 8094 PM‐resistant accessions, 60% were indigenous, while majority of the 40% exotic were from CIMMYT. Focused identification of germplasm strategy (FIGS), which identifies a set of similar plant genotypes with a greater possibility of containing specific target traits, was used to form a subset of 52 accessions (from 19,460) that have the potential to contain new PM resistance genes. Resistant accessions identified in the study have enriched the existing gene pool for PM resistance in wheat and will serve as a potential source for resistance in future. [ABSTRACT FROM AUTHOR]

Leaf rust (Puccinia triticina Eriks.) is a fungal disease of wheat (Triticum spp.), which causes considerable yield loss. Adult plant resistance (APR) is one of the most sustainable approaches to control leaf rust. In this study, field-testing was carried out across ten different locations, followed by molecular screening, to detect the presence of APR genes, Lr34+, Lr46+, Lr67+ and Lr68 in Indian wheat germplasm. In field screening, 190 wheat accessions were selected from 6,319 accessions based on leaf tip necrosis (LTN), disease severity and the average coefficient of infection. Molecular screening revealed that 73% of the accessions possessed known APR genes either as single or as a combination of two or three genes. The occurrence of increased LTN intensity, decreased leaf rust severity and greater expression of APR genes were more in relatively cooler locations. In 52 lines, although the presence of the APR genes was not detected, it still displayed high levels of resistance. Furthermore, 49 accessions possessing either two or three APR genes were evaluated for stability across locations for grain yield. It emerged that eight accessions had wider adaptability. Resistance based on APR genes, in the background of high yielding cultivars, is expected to provide a high level of race non-specific resistance, which is durable. [ABSTRACT FROM AUTHOR]

Background: Yellow or stripe rust, caused by the fungus Puccinia striiformis f. sp. tritici (Pst) is an important disease of wheat that threatens wheat production. Since developing resistant cultivars offers a viable solution for disease management, it is essential to understand the genetic basis of stripe rust resistance. In recent years, meta-QTL analysis of identified QTLs has gained popularity as a way to dissect the genetic architecture underpinning quantitative traits, including disease resistance. Results: Systematic meta-QTL analysis involving 505 QTLs from 101 linkage-based interval mapping studies was conducted for stripe rust resistance in wheat. For this purpose, publicly available high-quality genetic maps were used to create a consensus linkage map involving 138,574 markers. This map was used to project the QTLs and conduct meta-QTL analysis. A total of 67 important meta-QTLs (MQTLs) were identified which were refined to 29 high-confidence MQTLs. The confidence interval (CI) of MQTLs ranged from 0 to 11.68 cM with a mean of 1.97 cM. The mean physical CI of MQTLs was 24.01 Mb, ranging from 0.0749 to 216.23 Mb per MQTL. As many as 44 MQTLs colocalized with marker–trait associations or SNP peaks associated with stripe rust resistance in wheat. Some MQTLs also included the following major genes- Yr5, Yr7, Yr16, Yr26, Yr30, Yr43, Yr44, Yr64, YrCH52, and YrH52. Candidate gene mining in high-confidence MQTLs identified 1,562 gene models. Examining these gene models for differential expressions yielded 123 differentially expressed genes, including the 59 most promising CGs. We also studied how these genes were expressed in wheat tissues at different phases of development. Conclusion: The most promising MQTLs identified in this study may facilitate marker-assisted breeding for stripe rust resistance in wheat. Information on markers flanking the MQTLs can be utilized in genomic selection models to increase the prediction accuracy for stripe rust resistance. The candidate genes identified can also be utilized for enhancing the wheat resistance against stripe rust after in vivo confirmation/validation using one or more of the following methods: gene cloning, reverse genetic methods, and omics approaches. [ABSTRACT FROM AUTHOR]

Leaf rust caused by Puccinia triticina is an important disease of wheat and Lr24 gene confers resistance to all known pathotypes of P. triticina in India. Transcripts associated with the Lr24 mediated resistance were identified through transcriptome sequencing and further expression analysis of differentially regulated genes was performed using qPCR technique. De novo transcriptome assembly showed 66,415 and 68,688 transcripts in resistant and susceptible genotypes, respectively. The study revealed that 5873 genes unique to resistant; 6782 genes unique to susceptible, while 10,841 genes were common to both. Gene Ontology distribution statistics showed 1030 and 1068 CDS in biological processes; 1234 and 1326 CDS in cellular processes; 1321 and 1352 CDS in molecular functions, respectively. A total of 659 genes were found to be differentially expressed, of which 349 were upregulated and 310 were downregulated in resistant genotype. Pathway analysis of transcripts appeared in resistant genotype revealed that 279 transcripts had homology with genes involved in signal transduction, 18 transcripts in membrane transport, one transcript in signaling molecules. Real-time PCR study showed that most of the up-regulated defense related genes expressed in early hours indicating that a cascade of defense starts early in Lr24 mediated resistance, which successfully inhibited pathogen establishment. [ABSTRACT FROM AUTHOR]

Leaf rust caused by Puccinia triticina is an important disease of wheat and Lr24 gene confers resistance to all known pathotypes of P. triticina in India. Transcripts associated with the Lr24 mediated resistance were identified through transcriptome sequencing and further expression analysis of differentially regulated genes was performed using qPCR technique. De novo transcriptome assembly showed 66,415 and 68,688 transcripts in resistant and susceptible genotypes, respectively. The study revealed that 5873 genes unique to resistant; 6782 genes unique to susceptible, while 10,841 genes were common to both. Gene Ontology distribution statistics showed 1030 and 1068 CDS in biological processes; 1234 and 1326 CDS in cellular processes; 1321 and 1352 CDS in molecular functions, respectively. A total of 659 genes were found to be differentially expressed, of which 349 were upregulated and 310 were downregulated in resistant genotype. Pathway analysis of transcripts appeared in resistant genotype revealed that 279 transcripts had homology with genes involved in signal transduction, 18 transcripts in membrane transport, one transcript in signaling molecules. Real-time PCR study showed that most of the up-regulated defense related genes expressed in early hours indicating that a cascade of defense starts early in Lr24 mediated resistance, which successfully inhibited pathogen establishment. [ABSTRACT FROM AUTHOR]

Wheat being a staple food crop is essential for food security. Rust diseases like stem and leaf rust continues to be a serious threat to wheat production at national and international level. In recent years, powdery mildew disease is emerging as a threat to wheat production due to the climate change and intensive crop cultivation practices. Development of resistant cultivar is the most economical, reliable and sustainable way to control rusts and powdery mildew diseases. Stem rust, leaf rust and powdery mildew resistance genes viz., Sr2/Lr27/Yr30, Sr24/Lr24 and Sr36/Pm6 were pyramided using marker assisted backcross breeding approach. Based on phenotypic observations, five populations were selected at BC4F6 with respect to yield traits, leaf and stem rust and powdery mildew reactions. These populations were subjected to molecular marker analyses. Out of the five populations, Sr2+ were present in all the populations, while Sr24/Lr24 and Sr36/Pm6 was present in the fourth and fifth population. The identified population carrying Sr24/Lr24, Sr36/Pm6 and Sr2+ genes were stabilized at BC4F7 generation. The use of gene stacks/pyramids of major (Sr24/Lr24 and Sr36/Pm6) and minor gene (Sr2+) that confer resistance to most of the pathotypes of stem rust, leaf rust and powdery mildew could impart durability and sustainability to the cultivars than single gene deployment. [ABSTRACT FROM AUTHOR]