2015 BGRI Poster Abstracts

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Displaying 141 - 150 of 415

Genetic analysis and molecular mapping of resistance in barley to the heterologous rust pathogens Puccinia graminis f. sp. avenae and P. triticina

Stem rust is considered one of the most important threats to world cereal production. The appearance and spread of the wheat stem rust pathogen [Puccinia graminis f. sp. tritici (Pgt)] race Ug99 has caused great concern for global wheat production. Barley is a host to different specialized pathogen species such as Pgt, but is characteristically a near nonhost to most non-adapted (heterologous) rust pathogens such as the wheat leaf rust pathogen [P. triticina] and oat stem rust pathogen [P. graminis f. sp. avenae (Pga)]. The barley research line SusPtrit, developed for susceptibility to heterologous rust pathogens, is a useful resource to study the genetics of nonhost resistance and to clone the genes involved, particularly due to the recent availability of the genome sequence. Studies in wheat suggest that resistance genes that are effective against multiple rust pathogens (pleiotropic) such as Lr34/Yr18/Sr55, confer durable disease control. We intercrossed the sequenced barley genotype Morex with SusPtrit to determine the inheritance of resistance to the wheat leaf rust and oat stem rust pathogens. The F2 population segregated for a single dominant resistance gene in response to both heterologous pathogens Pga and Pt. Subsequent progeny testing and genetic analysis of the segregating F3 population will be performed to map and determine the relationship between the resistance genes. Large F2 populations were developed to fine map and clone the genes, and ultimately to transfer them into related crop species as an alternative approach for crop protection.

Primary Author: Haghdoust, The University of Sydney, Plant Breeding Institute, Australia

Keywords: stem rust, barley

Pst pathotypes and Yr gene postulation in Tunisian wheat

Yellow rust is a widely distributed wheat disease, that is more damaging in cooler, temperate regions. Epidemics have increased worldwide due to spread of aggressive high temperature tolerant strains PstS1/S2 that reached North Africa and southern France in 2004 and the widely virulent exotic Warrior race that spread in Western Europe in 2011. Resistant varieties are effective solutions to reduce the use of pesticides. However, races of the pathogen quickly overcome resistance genes. Therefore, selection of varieties with durable resistance to yellow rust is paramount for protection of both bread wheat and durum. To conduct a genetic control strategy, it is essential to study the pathotype dynamics and the resistance genes in wheat. We identified the pathotypes using the European and world differential sets that discriminate between 23 avirulence/virulence factors as well as simple sequence repeat (SSR) diversity among 20 Pst isolates collected in Tunisia in 2014. In addition, we postulated resistance genes in 28 Tunisian varieties and accessions at the seedling stage in order to identify the resistance diversity. Race 239 E175V17 was involved in the 2014 epidemic in Tunisia. Genetic analysis revealed that this race is exotic and distinct from the Northwestern European and Mediterranean groups, previously present in Tunisia. Resistance gene postulation indicated the presence of Yr3, Yr6, Yr7, Yr9+Yr4, and Yr25 in Tunisian varieties and accessions. Durum varieties Khiar and Salim, and bread wheat variety Tahent, were resistant to the local Northwestern European and Western Mediterranean pathotypes as well as the Warrior race. These varieties are thus short-term measures to address the yellow rust problem in Tunisia. Gene identifications will be confirmed by molecular and pedigree analyses of the accessions.Yellow rust is a widely distributed wheat disease, that is more damaging in cooler, temperate regions. Epidemics have increased worldwide due to spread of aggressive high temperature tolerant strains PstS1/S2 that reached North Africa and southern France in 2004 and the widely virulent exotic Warrior race that spread in Western Europe in 2011. Resistant varieties are effective solutions to reduce the use of pesticides. However, races of the pathogen quickly overcome resistance genes. Therefore, selection of varieties with durable resistance to yellow rust is paramount for protection of both bread wheat and durum. To conduct a genetic control strategy, it is essential to study the pathotype dynamics and the resistance genes in wheat. We identified the pathotypes using the European and world differential sets that discriminate between 23 avirulence/virulence factors as well as simple sequence repeat (SSR) diversity among 20 Pst isolates collected in Tunisia in 2014. In addition, we postulated resistance genes in 28 Tunisian varieties and accessions at the seedling stage in order to identify the resistance diversity. Race 239 E175V17 was involved in the 2014 epidemic in Tunisia. Genetic analysis revealed that this race is exotic and distinct from the Northwestern European and Mediterranean groups, previously present in Tunisia. Resistance gene postulation indicated the presence of Yr3, Yr6, Yr7, Yr9+Yr4, and Yr25 in Tunisian varieties and accessions. Durum varieties Khiar and Salim, and bread wheat variety Tahent, were resistant to the local Northwestern European and Western Mediterranean pathotypes as well as the Warrior race. These varieties are thus short-term measures to address the yellow rust problem in Tunisia. Gene identifications will be confirmed by molecular and pedigree analyses of the accessions.

Primary Author: Hamza, National Institute of Agronomy, Tunisia

Keywords: Tunisia, stripe rust, resistance

Analysis of the resistance to Zymoseptoria tritici in a Tunisian durum wheat landraces

Septoria tritici blotch (STB) caused by the fungal pathogen Mycosphaerella graminicola (anamorph: Zymoseptoria tritici) is one of the most important foliar diseases of durum wheat (Triticum turgidum ssp. durum) in Tunisia. It attacks plants from seedling stages to maturity causing serious yield losses. Breeding for resistance to STB in durum wheat can provide an effective, economic and environmentally-safe strategy to reduce yield losses. However, this is hampered by lack of sources of resistance. In this context, a collection of 420 accessions of durum wheat from the National Bank of Gene (BNG) were evaluated for resistance to two virulent isolates of Z. tritici, namely TunBz-1 (across two environments) and TM220 (across one environment) under field conditions at three different development stages. The evaluation scale was ranged from 0% (immune plant) to 100% (100% of leave covered with symptoms). Three effects were studied on the collection: environmental effect E1-E2 (years 2016-2017), isolate effect I1-I2 (TunBz-1 and TM220) and physiological stage effect S1-S2 (seedling and adult). Results highlighted different sources of resistance between both seedling and adult stages. Moreover, 51 and 67 accessions have differential response to the two studied isolates respectively in seedling and adult stage. Furthermore, the Venn diagram has identified 23 accessions in the collection that are resistant to both isolates at both stages and that resistance was stable across environments. These accessions are located mainly in the center of Tunisia. Resistance to isolate TunBz-1 is expressed since seedling stage and there is stability of this resistance throughout the environments. The center of Tunisia seems to be a diversity center that includes different sources of resistance to STB. This collection could be the subject of a genome-wide association study (GWAS) as it presents different types of STB resistance categories that can be targeted via SNPs.

Primary Author: Hamza-Ben Youssef, National Institute of Agronomy of Tunisia, INAT

Keywords:

Diversity of resistance genes in candidate cultivars for planting in the overwintering area of central Shaanxi province, China

China is the largest stripe rust epidemic area in the world. Central Shaanxi, as an important stripe rust overwintering zone for the disease serves as a “bridge” for the pathogen, where early sown wheat infected during the previous autumn provides inoculum for spring epidemics in more eastern regions. Studies of resistance and Yr-gene distribution among local candidate cultivars provide valuable insights into the influence of host genotype on selection of the rust pathogen population. A total of 183 local advanced lines from 2009 to 2011 were tested for seedling resistance with 12 Pst races in the greenhouse, and with mixed races at Tianshui in Gansu province. Gene postulations were based on the seedling response data and molecular markers. Four (2.2%) entries were resistant at all growth stages; 15 (8.2%) were resistant as adult plants; 164 (89.6 %) were susceptible to one or more races at the seedling or adult stages; and 40 were resistant to the currently prevalent races CYR32 and/or CYR33, but susceptible to at least one of the potentially important races Su11-4, Su11-5 and Su11-7, V26/CM42 and V26/Gui22. All entries showed seedling stage susceptibility at Tianshui. Postulated genes included Yr7, Yr9, Yr10, Yr17, Yr18, and Yr24/Yr26. Yr5, Yr15 and Yr61, currently effective against all Chinese races, were not present. Although advanced wheat lines bred in Shaanxi may be diverse our results show that most of them are highly susceptible to one or more prevalent or low frequency races in Shaanxi or adjacent Gansu. This situation indicates that Shaanxi farmers should be using partial adult plant resistances to reduce inoculum levels and hence reduce the amount of primary inoculum spread to more easterly wheat growing areas.

Primary Author: Han, State Key Laboratory of Crop Stress Biology for Arid Areas and College of Agronomy, Northwest A&F University, P. R. China

Keywords: China, stripe rust, resistance, diversity

On-farm seed production through Edget farmers' seed multiplier and marketing cooperative union: Practices and lessons from Basic

Shortage of seed of rust resistant varieties is a challenge of small holder farmers in wheat production. To successfully address this issue, one of the essential elements in wheat production system is farmer's access to quality seed of improved varieties. This paper presents the experience of on-farm basic and pre-basic seed production of newly released rust resistant wheat varieties. For the first time in the country, On-Farm basic and pre-basic seed production of wheat varieties was carried out in two districts/woredas (Silti and Soddo) of two specific locations (Loke faka and Wacho) where the Edget Farmers' Seed Multiplier and Marketing Union was licensed to produce some crop varieties (cereals and pulse), beginning in the 2011/2012 cropping season. Model farmers from primary cooperatives were selected based on the past experience they had with the union in producing certified seed. Selected farmers and relevant experts were trained on how earh seed of wheat is produced. Accordingly seed multiplication of four wheat varieties was conducted with frequent monitoring and evaluation at the course of multiplication.
As a result sufficient and quality basic seed of newly released wheat varieties was produced on-farm in both Loke and Wacho locations for own utilization and seed market. The result of the experiment revealed that it was possible to multiply quality wheat seed provided that partnership (with GOs and/or NGOs) is well-built and cooperative farmers do farm management practices as per the recommendations. On-farm seed production can be sustainable if the strong partnership exists among stakeholders, and wheat seed growers are given premium prices for their seed which is supported by the legal frame work that encourages the seed production of early generations. More importantly, the result of this experiment has a useful implication on government policies and strategies and government institutions' practice on farm early seed generation production and marketing.

Primary Author: Handoro, Hawassa Agriculture Research Centre

Keywords:

The wheat rust toolbox: Management and visualization of global wheat rust data

In recent years Pgt race Ug99 has moved out of East Africa posing a threat to other regions in Africa, Central and West Asia, and other regions where this pathotype had not been found. In Europe a new Pst population (Warrior and Kranich races) replaced less diverse pathogen populations during the years 2011-2014. To enable the tracking and monitoring of the evolution of pathogen populations, a new web/database management and display system called the Wheat Rust Toolbox was developed. This platform, hosted by the Global Rust Reference Centre, supports two major initiatives: 1) the Durable Rust Resistance in Wheat project (DRRW), for managing and visualizing wheat rust pathogen data - mainly related to the stem rust pathogen (Pgt) from Africa, Central and West Asia; and 2) the ENDURE wheat rust network for managing and visualizing stripe rust, including Pst race, virulence and genotype data for Europe. The presentation will provide an overview of data and tools available in the Wheat Rust Toolbox, the research infrastructure behind it, and how data are disseminated via several information platforms such as wheatrust.org, eurowheat.org and http://rusttracker.cimmyt.org/. Opportunities available for analyzing genotypic data (SSR and SNP) online via a web-based version of the POPPR integrated with the Wheat Rust Toolbox will be presented. Overall the results show that the collation of data in a standardized way across many countries leads to more robust and fast conclusions that will stimulate closer collaborations between partners.

Primary Author: Hansen, Aarhus University, Denmark

Keywords: GIS, surveillance, data

Leaf rust on triticale in the Czech Republic

farming because of lower demands for pesticide applications. Triticale as a hybrid of wheat and rye may possess disease resistances derived either or both from wheat and rye. In the Czech Republic the leaf rust pathogen isolated from triticale is Puccinia triticina. Triticale is usually resistant to the rye leaf rust pathogen (P. recondita). Limited information is available comparing P. triticina isolates collected from wheat and triticale. Manninger (2006, Acta Phytopathologica and Entomologica Hungarica 41: 93-100) pathotyped 82 isolates collected from wheat and triticale on 15 Thatcher NILs. More than 50% of isolates from wheat were virulent to Lr2b, Lr2c, Lr3, Lr11, Lr17, Lr21 and Lr26. Of 12 isolates from triticale 9 were virulent only to Lr2b and Lr2c and the other 3 isolates were virulent to Lr2b, Lr2c and Lr11. We inoculated 15 NILs and 7 triticale cultivars with 36 Pt isolates from wheat and 36 isolates from triticale. Characteristic differences between the reactions on NILs of isolates from triticale and wheat were not found except that virulence to Lr1 was much more frequent in isolates from wheat. Whereas isolates from triticale were virulent to all 7 tested triticale cultivars, isolates from wheat were virulent to only 3 triticales. In another experiment isolates from wheat and triticale were collected at four locations. Although paired isolates came from the same locations the responses of the NILs were different. Isolates from triticale for all four locations were virulent to a higher number of triticale cultivars than those from wheat. It seems that P. triticina races infecting triticale have changed over the last decade from having a narrow virulence range on bread wheat to the current situation of typical bread wheat races becoming specialized on triticale.

Primary Author: Hanzalova, Research Institute of Crop Production, Czech Republic

Keywords: leaf rust, triticale

Adult plant stem rust resistance of selected Egyptian and exotic bread wheat varieties

Resistance genes Sr2, Sr22, Sr24, Sr25 and Sr26 confer adult plant resistance to Pgt race TTKSK (=Ug99). Ten Egyptian wheat varieties and four bread wheat entries from CIMMYT were screened with five DNA markers to determine the presence of these genes, and were evaluated for stem rust response at Sakha and Sids during the successive growing seasons of 2015/16 and 2016/17. Varieties Giza 171, Sakha 94, Gemmeiza 11, and CIMMYT lines 6043, 6091, 6107 and 6197 were resistant with severities ranging from TrR to 5MR/MS. Sr2 was present in all entries; Sr24 was present in one local Egyptian cultivar (Misr2); Sr25 was present in Misr 1, Misr 2, Gemmeiza 9, Gemmeiza 11, and lines 6091 and 6197; and Sr26 was present in line 6197.

Primary Author: Hasan, Plant Pathology Research Institute

Keywords:

Placement of South African stripe rust in a global context and development of diagnostic tools for genotyping field samples

Stripe (yellow) rust, caused by the fungus Puccinia striiformis f. sp. tritici (PST), is a major global wheat disease. New PST strains that show higher infection rates and rapid adaptation to less favourable environmental conditions have been observed over the last 15 years. It has also continued to spread to areas where it was not previously recorded. In South Africa, stripe rust was first detected in 1996. In subsequent years three more PST races were observed, with what seemed to be a step-wise virulence gain. A better understanding of the South African PST pathotypes and how they fit in the global context is needed. We aimed to address this by sequencing the genomes of four historical PST isolates displaying the four distinct virulence profiles. This allowed us to characterise the genetic diversity between these stripe rust races and develop diagnostic markers to easily genotype current detections. We also placed the South African PST isolates in context with global PST isolates where sequence data was available. This analysis illustrates that the South African PST races are more closely related to PST from other African countries when compared to isolates from Africa, Europe and Asia. Through pairwise comparison of isolates, we identified 27 candidate effector genes showing specific polymorphisms between the four isolates that could be related to their distinct virulence profiles. We are currently undertaking gene expression profiling of these candidates to determine if these effectors are specifically upregulated during infection–a key characteristic of effector genes. This study has shed new light on the potential origin and adaptation of stripe rust in South Africa and provides tools for rapid genotypic classification of infections in the field.

Primary Author: Hester van Schalkwyk, Department of Plant Sciences, University of the Free State, South Africa

Keywords:

Characterisation of putative pleiotropic wheat leaf rust resistance gene Lr13

Evolution of rust pathogens continues to pose challenges to global wheat production. Major resistance (R) genes, which encode proteins of the NBS-LRR (Nucleotide-binding site, leucine-rich repeat) family, have been a valuable resource for breeders to minimise yield losses from infection. Many wheat varieties harbor numerous R genes that could be identified and cloned in order to engineer more sustainable disease control. The advent of targeted gene enrichment and next-generation sequencing (NGS) has allowed rapid cloning of specific R genes, thus enhancing efforts to pyramid these genes and investigate their underlying resistance mechanisms. Several R genes present different phenotypes in certain genetic backgrounds, and cloning them would be an important step towards uncovering their interactions. Hybrid necrosis is one such phenotype observed in crosses of wheat genotypes involving the R gene Lr13 and complementary genes, Ne1 and Ne2, occurring in different allelic forms. It was recently concluded that Lr13 and an allele of Ne2 are actually the same gene based on genetic and mutational studies. The capability of Lr13 to confer both leaf rust resistance and hybrid necrosis cannot be answered without first cloning it. The lack of tightly linked markers coupled with the proximal 2BS chromosomal location of Lr13 does not make it easily amenable to map-based cloning. The NGS-based pipeline MutRenSeq (mutagenesis and R-gene enrichment sequencing) was used on EMS (Ethyl methanesulfonate) induced, susceptible Lr13 mutants along with support from comparative genomics to ascertain candidate gene sequences for Lr13, which are at advanced stages of screening and confirmation. Definite proof that a single gene is involved will only come with transformation studies when the cloned Lr13 candidate transformed into a susceptible line confers both a resistance phenotype in the transgenic line and a necrotic phenotype in the offspring of crosses between the transgenic line and a line possessing Ne1.

Primary Author: Hewitt, CSIRO

Keywords: cloning

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