Rust reactions of lines in a wheat crossing block developed by the Bahri Dagdas International Agricultural Research Institute in 2014
BGRI 2015 Poster Abstract Akan
The Central Research Institute for Field Crops, Turkey
Rusts and drought are the principal yield-limiting factors for wheat production in the Central Anatolian region of Turkey. The aim of the study was to determine resistance sources in a crossing block of drought tolerant lines. Seedling tests involving all three rusts were carried out at CRIFC, Yenimahalle, in 2014. Inoculations were made with local Pgt (avirulent on differentials with Sr24, Sr26, Sr27 and Sr31), Pt (avirulent on differentials with Lr9, Lr19, Lr24 and Lr28) and a local Pst population. Reactions were scored 14 days post-inoculation on 0-4 (LR and SR) or 0-9 (YR) scales. Seventeen (19%) genotypes were resistant to stripe rust, 11 (12%) were resistant to leaf rust, and 17 (19%) were resistant to stripe rust.
Comparative analysis of rust resistant and susceptible wheat varieties in Pakistan
BGRI 2015 Poster Abstract Ali
International Maize and Wheat Improvement Center (CIMMYT) Pakistan Office
To reduce losses caused by rusts, regular and timely replacement of susceptible varieties with new high yielding, rust resistant varieties must occur. Data from a farmer survey carried out across Pakistan (Punjab, Sindh, KPK and Baluchistan) in 2014 enabled an analysis of the uptake of rust resistant variety NARC 2011. The empirical results indicated that the major sources of information that farmers obtained about NARC 2011 were research stations (83%), seed companies (7%) and fellow farmers (5%). Although production inputs were applied equally to both rust resistant NARC 2011 and rust susceptible wheat varieties the average yield of NARC 2011 (5,063 kg/ha) was superior to high yielding but rust susceptible varieties (4,446 kg/ha). Quality attributes of NARC 2011, including taste, color, dough kneading and chapatti making properties, were preferred by >70% of farmers). Seed availability and accessibility of NARC 2011 were major issues. Farmer awareness of rusts, especially the threat of exotic Pgt race Ug99, needs to be improved.
Rust responses of some Turkish, white grained, bread wheat genotypes in preliminary yield trials
BGRI 2015 Poster Abstract Akan
Central Research Institute for Field Crops, Turkey
Bread wheat is the most important cereal crop in Turkey. Rusts (caused by Puccinia spp.) are the most significant diseases affecting wheat yield and quality on the Central Anatolian Plateau. The purpose of this study was to identify the reactions of 198 Turkish, white seeded, winter wheat genotypes developed by the Central Research Institute for Field Crops (CRIFC) and entered in preliminary yield trials. Adult plant and seedling tests were conducted for stripe rust whereas only seedling tests were conducted for leaf rust and stem rust. Evaluations were carried out at CRIFC, İkizce and Yenimahalle, in the 2014 season. For adult plant stripe rust assessments the materials were inoculated with a local Pst population (virulent on differentials carrying Yr2, Yr6, Yr7, Yr8, Yr9, Yr25, Yr27, YrSd, YrSu, and YrA). Stripe rust development on each entry was scored using the modified Cobb scale when the susceptible check Little Club had reached 80S in June 2014. Coefficients of infection were calculated and values below 20 were considered to be resistant. Seedlings were inoculated with local Pgt (avirulent on differentials with Sr24, Sr26, Sr27 and Sr31), Pt (avirulent on differentials with Lr9, Lr19, Lr24 and Lr28) and the Pst population. Reactions were scored for each entry at 14 days post-inoculation on standard 0-4 (LR and SR) or 0-9 (YR) scales. At the seedling stage, 56 (28%), 43 (22%), and 31 (31%) genotypes were resistant to SR, LR and YR, respectively. Eighty three (42%) lines were resistant to YR at the adult stage.
Northern Kazakhstan and Western Siberia are major high latitude spring wheat growing regions on the Eurasian continent. Rust epidemics can cause serious crop losses in this region. For this purpose, the Kazakhstan-Siberian network for wheat improvement (KASIB) was created in 2000. Seventy wheat cultivars and lines from a KASIB nursery were characterized for seedling and adult plant resistance (APR) to leaf rust using Australian pathotypes in greenhouse and field experiments. A molecular marker (STS iag95) detecting 1RS and therefore genes located in the rye component of the 1BL.1RS translocation was used to verify the presence/absence of Lr26. Field assessments of the nursery were conducted at Cobbitty using mixed Pt pathotypes. Lr26 was detected in five cultivars (Bayterek, GVK-1916-9, Altayskaya 105, Ok-1, and Omskaya 36) based on seedling tests using seven pathotypes. This was confirmed using the SRS marker. Other genes postulated included Lr3a (in cv. GVK 1860/8, GVK 1369/2, GVK 1857/9, and GVK 1526-2) and uncharacterized gene/s in cv. Zhenis and Lutescens-166 SP 94). The majority of KASIB entries were susceptible in seedling tests to Pt, but varying levels of potentially useful resistance were observed in 23 genotypes tested in the field. Low infection types on seedlings and field resistance in cv. Tertsia, Aria, and Sonata suggested the presence of unknown gene/s of potential value that warrant further investigation. Future efforts to breed wheat varieties resistant to one or more of the cereal rust pathogens will require identification of resistance sources that differ from those already present. Understanding the dynamics of pathogenic variability in pathogen populations is also important in selecting appropriate resistances.
Identification of markers closely linked with adult plant leaf rust resistance gene Lr48 in wheat
BGRI 2015 Poster Abstract Vallence Nsabiyera
The University of Sydney, Plant Breeding Institute, Australia
Leaf rust is endemic to all wheat-growing regions of the world. Resistance to leaf rust in wheat cultivars is controlled either by all stage resistance (ASR) or by adult plant resistance (APR) genes. Although deployment of single ASR genes can provide high levels of resistance, these are usually overcome by virulence in pathogen populations. In contrast, individual APR genes often provide low levels of resistance and combinations of three to four genes are necessary to achieve adequate resistance for crop protection. This kind of APR has proven to be durable. APR gene Lr48 in a single plant selection of Condor (CSP44) was mapped on chromosome 2BS and was flanked by markers gwm429b (6.1 cM, distal) and barc7 (7.3 cM, proximal) (Bansal et al. 2008, Theor. Appl. Genet. 117:307-312). The present study was planned to identify markers more closely linked to Lr48. Selective genotyping by 90K Infinium Assay identified 27 SNP markers linked with Lr48. The SNP sequences were used to design Kompetitive Allele-Specific Primers (KASP). Eleven KASP markers showing clear clustering were genotyped on a RIL population using the CFX96 Touch™ real-time PCR detection system (Biorad, USA). KASP marker IWB72894 co-segregated with Lr48.
Complementary resistance genes Yr73 and Yr74 (YrA) in wheat selection Avocet R confer resistance to the non-adapted barley grass stripe rust pathogen Puccinia striiformis f. sp. pseudohordei.
BGRI 2015 Poster Abstract Dracatos
The University of Sydney, Plant Breeding Institute, Australia
This is the first study on the inheritance and genetic mapping of resistance to the barley grass stripe rust pathogen (Puccinia striiformis f. sp. pseudohordei – Psph) in bread wheat. Psph, commonly infects barley grass (Hordeum leporinum, H. murinum), but about 10% of commercial barley varieties are also susceptible. We tested over 500 diverse wheat accessions and determined that less than 20% were susceptible at the seedling stage suggesting wheat is an ‘intermediate’ host to Psph. The Australian variety Teal is highly susceptible to Psph at the seedling stage, whereas selections Avocet S and Avocet R are highly resistant and resistant, respectively. We used the Teal/AvocetR doubled haploid (DH) population to characterize the resistance of Avocet R to Psph and determine whether the complementary genes Yr73 and Yr74 (YrA resistance) in Avocet R conferred resistance to Psph. Phenotypic comparison of the Teal/AvocetR DH lines in response to both Psph and Pst showed that all DH lines carrying YrA were also resistant to Psph; however, fewer DH lines were susceptible to Psph suggesting additional resistance genes. Marker-trait association analysis detected three DArT-Seq markers significantly associated with resistance to Psph, two mapping to chromosomes 3DL and 5BL in the same regions as Yr73 and Yr74 and the third mapping to chromosome 4A. Single gene stocks with the 4A gene and combinations of the 5BL and 3DL genes will be used for monitoring avirulence/virulence within Australian Psph population. Genetic analysis of seedling-susceptible T/AvR DH lines as adult plants in the greenhouse determined that Teal and Avocet R each carried at least one APR gene effective against Psph.
The Global Rust Reference Centre (GRRC, www.wheatrust.org) was established in 2008 upon the request of CIMMYT and (ICARDA) and extended in 2011 by the support of the Borlaug Global Rust Initiative. GRRC serve as a global hub for investigating wheat rust fungi and can receive alive samples from all countries year round. The activities of GRRC comprise pathotyping of wheat yellow rust and wheat stem rust, as well as training of students and scientists, data handling and storage (databases) and reporting. The current research activities have a focus on evolutionary population biology, as well as basic genetic and genomic studies in yellow rust. The “Wheat Rust Toolbox” and the team behind has become part of the GRRC and all data generated by GRRC will be stored in this system. Data management, research activities and dissemination will be coordinated and integrated with partner information platforms at CIMMYT, ICARDA, Cornell University and other global partners. The quarantine greenhouse space has in recent years been enlarged by more than 50% allowing GRRC to take in more rust samples and students. The GRRC activities expanded significantly in 2011 and 2013 via grants from the Danish Strategic Research Council and the Ministry of Food, Agriculture and Fisheries. One of these initiatives, RUSTFIGHT, has a focus on understanding “aggressiveness” and involves a number of Danish and international partners, including ICARDA and CIMMYT, INRA and the John Innes Centre (UK), and private Danish plant breeding Industry.
A comparison of stem rust in oats and stripe rust in wheat: A Swedish example
BGRI 2014 Plenary Abstract Jonathan Yuen
Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences
A number of rusts affect grain crops in Sweden, but stem rust on oats and stripe (yellow) rust on wheat appear to create the greatest problems in production. The epidemiology of these diseases is intimately connected to the overall cropping patterns of these two crops. In Sweden, oats are only sown in the spring, thus forcing any overwintering pathogen to survive a Swedish winter. This is easiest for Puccinia graminis f. sp. avenae, which apparently completes its full, sexual life cycle on the abundant barberry plants. The presence of barberry and clear indications of sexual reproduction by P. graminis suggests that Pgt could be a problem on wheat, but there are only sporadic reports of stem rust on wheat. Wheat cultivars grown in Sweden possess few effective genes for resistance to stem rust, and the lack of rust is probably due to a lack of Pgt in the region. Given the resurgence of barberry in the landscape this implies that stem rust on wheat could be a major problem if (or when) the pathogen returns. P. striiformis, in contrast, can survive the Swedish winters on fall sown cereal crops, and thus it is the fittest clones that survive and dominate in the population. A large number of factors can affect this fitness, most markedly resistance genes in the cultivated wheat, but it is also possible that extended asexual reproduction can reduce the fitness of these persistent clones (Muller's ratchet) so that they can be displaced by fitter clones. Despite the widespread occurrence of barberry plants, we have not found any aecia of P. striiformis, although there does seem to be some genetic variation in the alternate host. Simple models that simulate the appearance and competition between different clonal lineages of the pathogen indicate that fitter individuals will eventually dominate the population, but their initial appearance will be difficult, since they are only detectable after enough generations have passed to increase the population size above a detectable level.
Global Pgt Initiative: An international genetic resource to combat stem rust
BGRI 2014 Plenary Abstract Les Szabo
USDA-ARS, Cereal Disease Laboratory
An important component of the management of wheat stem rust is an understanding of the population diversity of the pathogen, Puccinia graminis f. sp. tritici (Pgt). The discovery of “Ug99” resulted in renewed efforts on pathogen surveys, sample collections and pathotyping of Pgt, with a primary focus on Africa. In the last few years these efforts have been expanded to include other targeted regions, however a global effort is needed. The aims of the “Global Pgt Initiative” is: to capture and maintain living cultures that collectively reflect the entire global diversity of Pgt in the years 2014 - 2016; pathotype and genotype this collection; develop DNAbased diagnostic tools that will be able to rapidly detect shifts in Pgt populations, and provide an early warning system of the vulnerability of wheat to new virulent strains; and provide a genetic baseline for comparison of Pgt populations over time, both forward and backwards. This initiative will provide the wheat rust community with a geographically distributed, well characterized, living culture collection that represents the global diversity of Pgt; a global open access knowledge bank on Pgt pathotypes and genotypes; and advanced molecular diagnostic tools for rapid detection and tracking of Pgt populations. The Global Pgt Initiative represents the most comprehensive effort to capture and characterize the global diversity of Pgt and provide a unique resource to the global wheat rust community.
In 2010, Ethiopia experienced one of the largest stripe rust epidemics in recent history. Over 600,000 ha of wheat were affected, an estimated 60 million Ethiopian Birr ($US3.2 million) were spent on fungicides and large production losses were observed. Factors associated with the 2010 epidemic were conducive climatic conditions (prolonged rain and apparently optimal temperatures), large areas planted to susceptible cultivars, early infection and rapid spread of a virulent pathogen, a low level of awareness, and ineffective control measures. In 2013, highly favourable climatic conditions and early appearance of stripe rust showed remarkable similarity to the conditions observed in 2010, prompting fears of a similar major rust epidemic. However, no stripe rust epidemic developed in 2013. In contrast, only limited and localized outbreaks of stripe rust were observed in 2013; wheat crops remained in good condition and a good harvest was achieved. It seems that a series of positive and timely actions in Ethiopia contributed to the markedly different stripe rust situation in 2013 compared to 2010. The principle factors associated with the positive outcomes in 2013 are (i) effective promotion, plus rapid and widespread adoption of rust resistant wheat cultivars since 2010 - this dramatically reduced the vulnerability of the Ethiopian wheat crop; and (ii) timely and coordinated surveillance efforts, coupled to good information exchange amongst different stakeholders - this resulted in effective control and awareness campaigns that targeted emerging stripe rust outbreaks. A comparative analysis is presented which highlights the similarities and disparities between the 2010 and 2013 stripe rust situations in Ethiopia. The roles and contributions of different organisations are examined and an in-depth analysis of the biophysical conditions in the different years is presented.