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Single nucleotide polymorphism (SNP) is one of the most broadly distributed types of molecular variation in a genome which, along with the availability of costand labor-effective genotyping platforms, make it the marker of choice for many crops. Our work is aimed at the development of a dense set of genetically mapped SNP markers for low-cost high-throughput genotyping of wheat germplasm. Next generation sequencing of normalized cDNA libraries was used for developing gene-associated SNPs in polyploid wheat. A total of 7.5 million 454 reads were generated from cDNA libraries of 10 wheat cultivars from US and Australia and processed for discovering SNPs using a bioinformatical pipeline specifically designed for variant discovery in polyploid transcriptomes. A total of 25,000 high-quality SNPs distributed among 14,500 EST contigs were identified. All these SNPs were validated by comparison with RNAseq data generated from an additional set of 17 U.S. and Australian cultivars. A total of 9,000 genome-wide common SNPs were selected for designing an Illumina iSelect assay. Preliminary testing showed that more than 95% of SNPs produce high-quality genotype calls with up to 70% being polymorphic in a diverse sample of U.S. and Australian cultivars with a minor allele frequency >0.05. The assay is currently being used for studying patterns of genetic diversity in a worldwide collection of wheat cultivars and for developing a high-density SNP map. A long term goal of this initiative is to advance wheat research and breeding by developing genetic and genomic tools for efficient analysis of agronomic traits using high-resolution linkage and association mapping and deploying SNP markers in breeding programs
Primary Author: Eduard Akhunov, Department of Plant Pathology, Kansas State University, USA
Monsanto’s Beachell-Borlaug International Scholars (MBBIScholars) Program was established on March 25, 2009, on Dr. Norman Borlaug’s 95th birthday. Monsanto initially funded the MBBIScholars program for $10 MM ($2 MM per year for 5 years) and extended the program with a second grant for $3 MM ($1 MM per year for 3 years). As of February 2015 (6 Years of funding) the program has supported 70 students. The 70 MBBIScholars were selected from 359 applications. MBBIScholars are from 25 countries with India having 20 scholars. MBBIScholars from other countries are – Argentina 3, Bangladesh 2, Brazil 2, China 4, Columbia 4, Ecuador 1, Egypt 1, England 1, Ethiopia 4, Kenya 2, Korea 2, Iran 3, Italy 1, Mali 1, Nepal 2, Pakistan 1, Philippines 1, Syria 2, Tajikistan 1, Thailand 1, Tunisia 1, USA 4, and Uruguay 2. Forty scholars studied wheat breeding and 30 studied rice breeding. Twenty seven scholars were young ladies. Applications for the 7th round were due on or before February 1, 2015. A unique feature of the MBBIScholars Program is the requirement that scholars must complete part of their PhD program in both developed and developing/transition countries. Scholars have worked with developed country scientists as follows – Australia 4, Canada 3, USA 43, and Western Europe 20. The program pays for the MBBIScholars to participate in a 3 day Leadership course prior to attending the World Food Prize during their first 2 years. It has been a good experience to see MBBIScholars gain self-confidence after attending the Leadership Course and World Food Prize, and as they study and conduct research in developed and developing/transition countries. They also gain many lifelong contacts in the plant breeding community. Based on the current funding agreement with Monsanto, the final round of MBBIScholars will be selected from applications due February 1, 2016. In view of the great success of this model of training international plant breeders, it would be highly desirable for donors to support and extend this PhD training program to include additional crops of interest in developed and developing countries.
Primary Author: Edward Runge, Texas A&M University
Wheat rusts, caused by the fungal pathogen Puccinia sp. are serious economic diseases of wheat worldwide. Surveillance, monitoring and new virulence identification are prerequisites for future race prediction and for effective breeding programs. Therefore, we decided to compile the endeavours done for surveillance over eight cropping seasons in Lebanon. The extensive field surveys were conducted yearly in major bread and durum wheat areas over the period 2009-2017 using the Borlaug Global Rust Initiative surveillance protocols. Over eight years, 136 locations were surveyed, 56 samples were collected from mainly stripe and stem rust, and X samples were phenotyped using a robust set of standards differentials lines used worlwide at Tel Hadya - ICARDA, 6 phenotyped at INRA - Grignon, 4 phenotyped at the Global Rust Reference Center (GRRC), until the season 2015-2016 the cereal rust laboratory at LARI became autonomous in race analysis. Six samples were genotyped. The latest phenotyping showed that pathotypes had combinations of the virulence for the widely deployed genes Yr2, Yr6, Yr7, Yr8, Yr9, Yr25 and Yr27 resembling to the aggressive strain PstS2, the invasive high temperature tolerant isolate. Resistance genes Yr1, Yr3, Yr4, Yr5, Yr10, Yr15, Yr17, Yr32, and YrSP were effective against all isolates. Race typing of the stem rust sample using the North American stem rust differential sets indicated presence of TKTTF in surveyed wheat growing areas as well as at ICARDA's research station in Terbol. Identified races have been used in field artificial inoculation of ICARDA's breeding program during the last two years. In conclusion, the races PstS2 and TKTTF were the dominant prevalent races in the country for yellow and stem rust respectively. This information could be useful for the region for better integrated disease management and wider diversification of resistance genes deployment in breeding programs.
Primary Author: El Amil, Lebanese Agricultural Research Institute
Hybrid wheat is a promising technology to increase yields worldwide. High seed production costs and low heterosis are the main constraints for the development of hybrid wheats. Maximizing heterosis, and selection and utilization of appropriate morphological, floral and flowering traits to optimize outcrossing are important for hybrid seed production. For an efficient hybrid wheat seed production, high anther extrusion is required to promote cross fertilization and to ensure a high level of pollen availability. A pool of 200 elite spring bread wheat male parental lines was visually assessed for anther extrusion in the plastic-house and field environments. Genome-wide association studies (GWAS) for anther extrusion was carried out using a total of 12725 SNP markers. A wide genotypic variance was observed. Several significant (|log10(P)| > 3.0) marker trait associations (MTAs) were detected. Both genotypes and environment influenced the magnitude of the anther of extrusion. The consistently significant markers could be helpful to introduce anther extrusion trait in high yielding varieties and consequently improve hybrid-seed production in wheat.
Primary Author: El Hanafi, International Center for Agricultrural Research in Dry Areas
Durum wheat (Triticum durum Desf.) is a major cereal crop grown globally. The terminal reduced moisture and heat occurring at the flowering phase are among the main constraints to its production. The molecular basis of tolerance to these threats remains mostly unknown. A subset of 100 genotypes derived from a collection of 384 accessions originating from different countries were investigated for their root growth and architecture under water-limited and well-watered treatments. Two protocols were used, "clear pot" for seminal root angle and "pasta strainer" for mature root angle evaluation. This study reveals that root architecture did not change depending on water treatment. A genotypic variation in root angle was found and two categories of root types were identified: genotypes with (i) superficial and (ii) deep rooting systems. In order to investigate the impact of each root type on yield, all genotypes were tested in the field at multiple locations and under different water regimes. The same set was also tested for heat tolerance in the field under rainfed conditions. Heat was imposed by placing a polytunnel at flowering time to raise the temperature of 10 degrees. The yield, thousand kernel weight and grain number per spike, were evaluated and compared to assess grain fertility, considered as a key trait of heat tolerance. The complete set was genotyped and a genome scan using 8173 SNPs markers developed by 35K Axiom array allowed to identify the genomic regions influencing drought and heat adaptation mechanisms. The pyramiding of this genomic regions could lead to an improved resilience to climate change and increase durum wheat productivity.
Primary Author: El Hassouni, Mohamed 5th University / ICARDA
Leaf rust resistance genes Lr9 and Lr19 were previously highly effective against the most predominant races of Puccinia triticina in Egypt. In 2015/2016 growing season, susceptible field reaction was recorded on these two genes where rust severity reached about 40S for Lr9 and 5S for Lr19 under Egyptian field conditions at four locations i.e. El-Behira, El-Minufiya, El-Qalubiya and El-Fayom governorates. Eight leaf rust field samples were collected from these governorates (four from each of Lr9 and Lr19). Forty single isolates were derived from the collected samples of Lr9 and Lr19 (each with 20 isolates). Eight pathotypes were identified from Lr9 and only two pathotypes were identified from Lr19. The most frequent pathotypes virulent to Lr9 were KTSPT (30%) followed by TTTMS (25%). Moreover, the other pathotypes ranged from 5 to 10%. Whereas, the most frequent pathotype virulent to Lr19 was CTTTT (85%) and the lowest PKTST was 15%. Pathotypes i.e. PRSTT, NTKTS and TTTMS identified from Lr9 were more aggressive on most of the tested leaf rust monogenic lines, as they were virulent to 36, 35 and 35 lines, respectively from a total of 39 lines. The two pathotypes; PKTST and CTTTT identified from Lr19 were virulent to 36 and 35 lines, respectively. Moreover, leaf rust pathotypes i.e. NPTNK and PRSTT from Lr9 and PKTST from Lr19 were the most aggressive on the tested wheat cultivars at seedling stage. The Lr2a was the most effective leaf rust resistance genes against the tested pathotypes at adult plant stage. Wheat cultivars Misr 1, Misr 2 and Nubariya 1 were the most resistant cultivars against the tested pathotypes at adult plant stage.
Primary Author: El-Orabey, Plant Pathology Research Institute
Leaf rust caused by Puccinia triticina is one of the most historical and economically important wheat diseases. Breeding for new cultivars with effective gene combinations is the most promising approach for reducing losses due to leaf rust. Wild emmer wheat, Triticum dicoccoides, the progenitor of modern tetraploid and hexaploid wheats, is an important resource for new variability for disease resistance genes. An accession of T. dicoccoides acc. pau4656 showed resistance against prevailing leaf rust races in India, when tested at the seedling and adult plant stage. The introgression line, developed from the cross of the leaf rust resistant T. dicoccoides acc. pau4656 and the susceptible T. durum cultivar Bijaga yellow, was crossed with T. durum cultivar PBW114 to generate recombinant inbred lines (RIL) for mapping leaf rust resistance gene(s). RIL population was screened against highly virulent leaf rust race 77-5 at seedling stage and inheritance analyses revealed the segregation of two leaf rust resistance genes. The genes have been temporarily designated as LrD1 and LrD2. A set of 387 SSR marker was used for bulked segregant analysis (BSA). The markers showing diagnostic polymorphism in the resistant and susceptible bulks were amplified on whole of the population. Single marker analysis using MapDisto software placed LrD1 on the long arm of chromosome 6A linked to the SSR marker Xwmc256 and LrD2 on long arm of chromosome 2A close to the SSR marker Xwmc632. T. durum cv. PBW114 used in the present study was also resistant to leaf rust at the seedling stage. So one of these leaf rust resistance genes might have been contributed by the PBW114 and other by T. dicoccoides. The current study identified valuable leaf rust resistance genes for deployment in wheat breeding programme.
Primary Author: Elkot, School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana-141004 India
Plants are generally non-hosts to most diseases. Barley is a host to Puccinia striiformis f. sp. hordei, but is a near non-host to P. striiformis f. sp. tritici (Pst) and to P. striiformis f. sp. pseudohordei (Psp), which cause stripe rust on wheat and barley grass (Hordeummurinum, H. leporinum), respectively. This study was carried out to determine the inheritance of resistance in barley line 81882/BS1 using the mapping population: 81882/BS1/Biosaline-19. 81882/BS1 is a H. vulgare derivative of cv. Vada, carrying an introgression from H. bulbosum on chromosome 2HS, and Biosaline-19 is susceptible to both Pst and Psp. Phenotyping of F3 lines with Psp culture 981549 and Pst pathotype 134 E16 A+ showed that 81882/BS1 carried two genes for resistance to Psp, and three genes for resistance to Pst. Cytogenetic analysis and molecular mapping were performed to further characterize the resistance of 81882/BS1 to Psp. Joint phenotypic and cytogenetic analysis indicated that at least one of the genes for resistance to Psp was associated with the H. bulbosum introgression previously located on chromosome 2H (Zhang unpublished). Preliminary molecular mapping of 15 non-segregating resistant and 15 non-segregating susceptible lines using >10K DArTseq molecular markers located the second gene on chromosome 1H. This gene was probably contributed by Vada. Further studies are underway to confirm the locations of these two loci by fine mapping.
Primary Author: Elmansour, The University of Sydney, Plant Breeding Institute, Australia
Wheat stem rust is one of the major wheat yield limiting factors in Ethiopia. A stem rust epidemic occurred in the wheat belts of Arsi and Bale zones in the 2013-2014 crop season caused by Pgt race TKTTF that is virulent to the widely grown Ug99-resistant variety Digelu. This epidemic highlighted the need for wheat varieties with resistance to multiple Pgt races. This study was therefore, carried out to evaluate the reaction of the major Ethiopian varieties and advanced breeding lines against the dominant Pgt races in Ethiopia. Races TKTTF, TTKSK, TRTTF and JRCQC were isolated from field samples and multiplied on the susceptible cultivar McNair starting in May 2014. Four wheat stem rust nurseries, each inoculated with a single Pgt race, were established at Kulumsa and monitored from July through October, 2014. Each nursery included 34 entries in two replicates and 137 entries in a single replicate, augmented with six sets of five repeating checks. An additional nursery established at Debre Zeit, containing 551 entries in an augmented design, was evaluated with the epidemic Pgt race TKTTF. These entries included the most relevant Ethiopian bread and durum wheat breeding lines and cultivars, and 34 seedling-susceptible lines to evaluate the race-specificity of adult plant resistance. Stem rust severities for the four races ranged from trace to 80 %. Out of all entries evaluated, 10 were resistant to all four Pgt races, while 11 entries were effective to three of the four races. At Debre Zeit, 31.4% of the entries were resistant to Pgt race TKTTF. This study showed that rapid isolation and increase of Pgt races in Ethiopia is possible to facilitate field screening of breeding lines to select for candidate cultivars with resistance to multiple virulent races of Pgt.
Primary Author: Endale Hailu, Ethiopian Institute of Agricultural Research (EIAR)
To inform breeders and growers of important changes in virulence and to facilitate development and deployment of resistant cultivars, isolates of wheat rust fungi are routinely evaluated on seedlings of a set of differential wheat lines containing different resistant genes. However, the methods used to evaluate and report virulence changes in most regions of the world seem inadequate for accomplishing these goals and could be improved by adherence to three principles. Firstly, for each region, the resistance genes in the set of differentials should match the effective genes in contemporary cultivars and breeding lines. Most differential sets contain several resistance genes that have been ineffective for decades and do not contain genes found in cultivars and breeding lines. Given the importance of genes for race-specific adult-plant resistance, these should be included in differential sets. Secondly, intermediate reactions on differential lines that had been highly resistant are important warnings of gradual increases in virulence. Naming races requires isolates to be either virulent or avirulent on each line in a fixed set of differentials and is a hindrance to identifying gradual changes in virulence on currently effective genes. Utilizing virulence formulae with a designation for intermediate virulence (e.g. parentheses around the gene or differential) seems to be a simple solution for both documenting partial virulence and for easily changing differentials to match genes in cultivars and breeding lines. Thirdly, the method for evaluating virulence against a particular differential should predict the result of that host-pathogen interaction in the field. Growth stage and environmental conditions are important for expression of some resistance genes, and all currently effective genes are not likely to be expressed under the same conditions. Following these principles will make virulence surveys more predictive of important changes in the field and thereby contribute to more effective management of rust diseases.
Primary Author: Eugene Milus, University of Arkansas
