Bangladesh Agricultural Research Institute
Paritosh Kumar,Malaker, Krishna Kanta, Roy, Md. Mostofa Ali, Reza, Naresh Chandra Deb, Barma, Md., Farhad, , , , , , , , , , , , , , , , , , , ,
Leaf rust is one of the major diseases of wheat in Bangladesh. The farmer fields and trial sites were regularly surveyed for rust assessment from 2010-2011 to 2016-2017 wheat growing seasons. Disease severity was recorded following BGRI protocols. Percentage of fields infected with leaf rust and the levels of disease severity varied with genotype, year, planting time and survey sites. Timely planted wheat either escaped or had less disease compared to late planted crop. Among our cultivated varieties, Shatabdi was either free from infection or exhibited only trace severity with resistant reaction. Variety Saurav, Bijoy, BARI Gom 27 , BARI Gom 28 , BARI Gom-29 and BARI Gom-30 were consistently free from leaf rust infection. BARI Gom 25 and BARI Gom 26 showed low to moderate disease levels with MRMS-MSS reactions, while the variety Prodip demonstrated moderate to high disease severity with susceptible response and it needs to be replaced by resistant variety to sustain wheat productivity.
Punjab Agricultural University
Parampreet,Kaur, Preeni, Bawa, Bharat, Yadav, Ajay, Mahato, Inderjit, Yadav, Priti, Sharma, OP, Gupta, Parveen, Chhuneja, NS, Bains, Jaroslav, Dolezel, Bikram Singh, Gill, J, Khurana, NK, Singh, Kuldeep, Singh, Kelly, Eversole
Diploid A genome wheat species harbor immense genetic variability which has been targeted and proven useful in wheat crop improvement. Further, the development and deployment of sequence based markers in wheat using survey sequences from next generation sequencing has opened avenues for comparative analysis, gene transfer and marker assisted selection (MAS) using high throughput cost effective genotyping techniques. Chromosome 2A of wheat is known to harbor several economically important genes. The present study aimed at in silico identification of genes corresponding to full length cDNAs and mining of SSRs and ISBPs from 2A draft sequence assembly of Chinese Spring for marker development. In totality, 1029 primer pairs (478 gene based, 501 SSRs and 50 ISBPs) were used to screen for polymorphism in diploid A genome species i.e., T. monococcum and T. boeoticum that identified 221 polymorphic loci. Out of these, 119 markers were mapped in T. monococcum X T. boeoticum RIL population. The enriched 2A genetic map constituted 161 mapped markers with final map length of 549.6 cM. Further, the utility of this enriched genetic map was demonstrated towards the fine mapping of adult plant resistance (APR) QTL, QYrtm.pau-2A against stripe rust. Using composite interval mapping, a QTL was detected between G45 and G54 markers explaining 19% of phenotypic variance. The primer sequences of the two genic markers were used to find the scaffold of 343 kb from IWGSC WGA V0.4 data. Thirty five simple sequence repeat markers were designed from the scaffold sequence which are being used for the fine mapping of QYrtm.pau-2A.
Dryland Agricultural Research Institute, Sararood branch, AREEO, Kermanshah, Iran
Ehsan,Lorestani, Reza, Haghparast, Mohammad Reza, Jalal Kamali, Ahmed, Amri, , , , , , , , , , , , , , , , , , , , , ,
Yellow rust (Puccinia striiformis Westendorf f. sp. tritici) is an important disease on wheat worldwide and especially in the highlands of West and Central Asia. Wheat landraces are composed of complex, variable, genetically dynamic and diverse populations, in equilibrium with both biotic and abiotic stresses prevailing in their environment. A germplasm collection consisting of 380 durum wheat accessions conserved at National Plant Gene Bank (Seed and Plant Improvement Institute, Iran) with worldwide origins, along with four check varieties were screened for resistance to yellow rust, and were also evaluated for several drought adaptative traits under rainfed conditions during 2009-10 cropping season at Sararood agricultural research station, Kermanshah, Iran. The study was conducted to quantify the phenotypic diversity and exploring durum accessions for yellow rust resistance, and to characterize the agronomic profile of different subsets of accessions for reaction to local yellow rust races. High natural infection, caused by the predominant virulent races of 6E8A+ and Yr27+, was experienced as shown by the 100 S reaction of the check bread wheat ?Sardari? and several highly susceptible accessions. The tested accessions exhibited significant variation in yellow rust severity, ranging from highly resistant to highly susceptible. Approximately 12.1% of accessions were found to be resistant to yellow rust, 9.5% were moderately resistant, 10.5% were moderately susceptible and 67.9% were susceptible. The germplasm showed a relatively modest response to yellow rust as expressed by a decrease in 1000-kernel weight (TKW) and a lower yield of the susceptible vs. resistant subsets by 11.4% and 19.9%, respectively. A comparison of foreign vs. Iranian resistant accessions, revealed higher yield productivity, higher TKW, and shorter plant height for the foreign accessions. Durum germplasm may constitute valuable genetic material for breeding new durum varieties characterized by high yield productivity under rainfed conditions and with adequate resistance to yellow rust.
Lebanese Agricultural Research Institute
Claude de Vallavieille-Pope, Marc Leconte, Mogens Hovmøller, Kumarse Nazari
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.
Northwest A&F University
Yanping,Fu, kang, Wang, Yingbin, Hao, Zhensheng, Kang, , , , , , , , , , , , , , , , , , , , , ,
Wheat adult plant resistance (APR) to stripe rust, a non-race-specific and durable resistance, is ideal for breeding. However, the knowledge concerning APR mechanism is largely limited. In order to further investigate the molecular basics of APR to provide guidance for wheat breeding, we conducted the transcriptome sequencing of wheat XZ9104 infected by Puccinia striiformis f. sp. tritici (Pst) at seeding and adult stages, respectively. Comparative analysis revealed that many WRKY transcription factors (TFs) may participate in the APR to stripe rust, of which, TaWRKY79 transcript levels were sharply elevated at the early infection stage in seedling plants. To dissect the relationship between TaWRKY79 and APR, we further studied the function of TaWRKY79. Subcellular localization showed that TaWRKY79 is located in the nuclear, and TaWRKY79 protein contains a separated region for mediating transcriptional activation at the C-terminus (246-328 aa) by yeast one-hybrid analysis. When TaWRKY79 was silenced by virus-induced gene silencing (VIGS) in seedling plants, the Pst growth was attenuated, with shortened hyphae, reduced hyphal branches and colony size. Meanwhile, the expression of TaWRKY79 was highly suppressed by salicylic acid (SA) but induced by jasmonic acid (JA) in seedling of wheat, and the transcription levels of LOX2 and PDF2.2 were significantly reduced, but the expression of PR1.1 was enhanced in TaWRKY79 knocking-down seedlings of wheat. Hence, these findings suggested that TaWRKY79, as a SA/JA cross talk, might play a negative role in resistance defence response to Pst infection at seeding stage by simultaneously activating the JA-dependent pathway and suppressing the SA-dependent pathway.
Department of Plant Pathology, North Dakota State University, Fargo, ND
James,Kolmer, Maricelis, Acevedo, , , , , , , , , , , , , , , , , , , , , , , , , ,
Leaf rust, caused by Puccinia triticina Erikss. (Pt), is the most widespread wheat rust disease. Information on the virulence and genetic diversity of Pt is important for understanding the pathogen evolution, and thus effective management of wheat leaf rust. We used 20 Thatcher wheat near isogenic lines to study virulence diversity of 102 Pt isolates collected from tetraploid wheat, common wheat, and Triticale worldwide. Seven races were found among 57 isolates collected from tetraploid wheat while 21 races were observed among 40 common wheat type isolates. Four races were identified among the five isolates collected from Triticale. A subset of 30 Pt were genotyped using the Restriction-Associated DNA (RAD)-Genotype By Sequencing (GBS) adapted for the Ion Torrent sequencing platform. Phylogenetic analysis on 30 isolates using 2,125 SNP markers showed eight clusters supported by high bootstrap values. We observed higher genotypic diversity in common wheat type isolates compared to that in tetraploid wheat type isolates. Generally, there was a correlation between virulence phenotypes and SNP genotypes. Phylogeny results suggest that RAD-GBS is promising as a new technique for the study of population genetics in P. triticina.
Crop Breeding Institute
Sripada Udupa, Charles Mutengwa, Peter Mavindidze
Host resistance is the most effective and economical method to minimize yield losses caused by rusts. The aim of this study was to detect the presence of resistance in 75 wheat genotypes. The presence of the genes viz. Sr2, Sr24, Lr34, Lr37, Lr46 and Lr68 was investigated using simple sequence repeat and sequence tagged site markers. Quantitative aspects of resistance to leaf rust were assessed through infection response (IR), disease severity (DS), coefficient of infection (CI), disease incidence (DI), leaf tip necrosis (Ltn) and area under disease progress curve (AUDPC) under natural epidemics. Highly significant (p <0.001) differences were observed among the genotypes for CI, DI, AUDPC and relative AUDPC (rAUDPC). Twenty genotypes exhibited high levels of adult plant resistance, recording CI less than 20% and AUDPC less than 300%, with moderately susceptible to susceptible reactions. The most frequently occurring gene was Lr46 (21%), followed by Lr68 (20%), Lr34 (19%) andLr37 (11%). The stem rust resistance gene Sr24 was absent in all the genotypes. Selection for Lr34 and Lr46 based on Ltn alone can sometimes be misleading because of its variable expression in different genetic backgrounds.
La Trobe University
Antony Gendall, Hans Daetwyler, Matthew Hayden
Wheat stem (Sr), leaf (Lr) and stripe (Yr) rust pathogens are among the most destructive fungal diseases threatening global wheat production. We utilized 2300 wheat accession including worldwide landraces, cultivars, breeding materials and 341 synthetic accessions backcrossed with three widely grown Australian cultivars (Annuello, Yitpi and Correll) to investigate rust resistance under wide environmental conditions. The germplasm was genotyped with 90K SNP chip, and was phenotyped for two seasons in three different environments against Sr and Lr and in four different environments against Yr. Different environments for each trait showed significant correlation with mean r values of 0.53, 0.23 and 0.66 for Lr, Sr and Yr; respectively. Single-trait genome wide association (GWAS) revealed several environment-specific QTL and multi-environmental QTL distributed on all chromosomes except 6D. Multi-trait GWAS confirmed a cluster of Yr QTL on chromosome 3B (within 8.3 cM) as well as a QTL for Sr and Lr on chromosome 3D. Linkage disequilibrium and comparative mapping showed that at least three Yr QTL exists within the 3B cluster including the durable rust resistance gene Sr2/Yr30. The same region was effective against Sr resistance but did not pass the stringent significant threshold in two environments. The 3D QTL was found mainly in the synthetic germplasm with Annuello background which is known to carry the Ag. elongatum 3D translocation carrying Sr24/Lr24 resistance gene. Interestingly, estimating the SNP effect using BayesR method showed that the correlation among the highest 5% QTL effects across environments were lower than that for the small effect QTL with differences in r values of 0.25 and 0.2 for Lr and Yr respectively. These results indicate the importance of small effect QTL that cannot be captured using GWAS in achieving durable rust resistance. The detected QTL in this study are useful resources for improving bread wheat resistance to rust diseases.
Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221005, India
Punam Singh Yadav, Ramesh Chand, Vinod Kumar Mishra, Uttam Kumar, Arun Kumar Joshi
The Sr2 gene has been used extensively in bread wheat improvement for durable stem rust resistance. Interestingly, the resistance of Sr2, associated with the pleotrophic gene Pbc expressed as pseudo-black chaff (PBC), is tightly linked with Yr30/Lr27/Pm genes conferring multiple disease resistance. The linkage map of chromosome 3BS revealed that Sr2 is 0.43cM away from lesion mimic (lm) locus. The RIL population (Yangmai#6 ? Sonalika) of 88 lines including parents where Sonalika carries Sr2 and lm while Yangmai#6 is deficient to both was evaluated for three years (2013-2016). The objective was to determine if this fragment is inherited as one unit and provides resistance to multiple diseases. Twenty four SSR markers distributed between 0.00 to 7.09cM on 3BS covering both Sr2 (5.57cM) and lm locus (6.0cM) were studied in the RIL population. Phenotyping was done for Sr2 associated PBC and lesion mimic along with disease severity for leaf rust, and spot blotch. Positive and significant correlations were observed between leaf stem rust resistance with Sr2 carrying PBC and lm. However, lines with lm either alone or with Sr2 (showing PBC) exhibited spot blotch susceptibility. The reverse situation does not hold not true where genotypes carrying Sr2 alone showed no correlation with spot blotch resistance. This indicates that the Sr2 complex is inherited as a single unit. Use of 24 SSR also suggest that Sr2 and lm loci are tightly linked and inherited together. The co-inheritance of Sr2 and lm ensures the stability and durability of rust resistance. However, the discouraging observation of spot blotch susceptibility due to lm gene suggests a limitation in achieving multiple disease resistance in environments where spot blotch is important. We identified two transgressive segregates in the population showing least expression of lm despite the presence of Sr2 and lm together.
International Center for Agricultrural Research in Dry Areas
Wuletaw,Tadesse, Najib, Bendaou, , , , , , , , , , , , , , , , , , , , , , , , , ,
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.