All BGRI Abstracts

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Identification of naturalized and cultivated Berberis species in South Africa

Keet University of Stellenbosch, South Africa
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While Africa is home to three Berberis species (B. holstii, B. hispanica and B. vulgaris), genera of the family Berberidaceae do not occur naturally in South Africa. However, due to the trade in ornamental plants, a total of 11 Berberis species, 11 cultivars and 8 hybrids were historically and/or are currently cultivated in the country. The current invasive status of most of these species is unknown, but two naturalized Berberis populations were recently discovered. B. julianae was found in the Golden Gate Highlands National Park in eastern Free State province, and B. aristata was found in the Woodbush Forest Reserve in Limpopo province. Since several Berberis species could act as alternate hosts for Puccinia graminis and P. striiformis, a phylogenetic study was conducted to identify both naturalized species, as well as several cultivated specimens. One of the cultivated specimens was identified as B. vulgaris, a species well known for its susceptibility to P. graminis. Knowledge gained from this study will be used to intensify the search for more naturalized Berberis populations, as well as to assess the potential threat to wheat cultivation in the country.

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Crosstalk between CBL-CIPK and SA signaling pathways in wheat-Puccinia striiformis f. sp. tritici pathosystem

Guo State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, PR China

Intracellular calcium changes during plant–pathogen interaction are essential early events leading to both local and systemic acquired resistances. Salicylic acid, a critical messenger, is also required for both responses. However, the relationship between the CBL-CIPK and SA signaling pathways during wheat–Pst interaction is unclear. In this study, we isolated seven wheat CBL and 11 wheat CIPK genes and designated them as TaCBL1, 2, 3, 4, 6, 7, 9 and TaCIPK2, 5, 7, 9, 10, 14, 15, 17, 23, 31, 32. Some wheat CBLs and CIPKs were functionally characterized. Concurrently, wheat TaNPR1 as a master regulator of SA-mediated host response during Pst infection was functionally characterized. Silencing of TaCBL4, TaCIPK10 and TaNPR1 permitted increased rust development in a wheat variety that was resistant to Pst pathotype CYR23. Decreased levels of salicylic acid (SA) were observed in TaCBL4- and TaCIPK10-silenced wheat plants. Yeast two-hybrid and biomolecular fluorescence complementation (BiFC) revealed that TaCIPK10 interacted with both TaCBL4 and TaNPR1. These results suggest that a TaCBL4-TaCIPK10-TaNPR1 complex is involved in innate immunity of wheat to Pst.

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Responses of some Turkish winter durum wheat genotypes in preliminary yield trials to stem, leaf and stripe rusts

Mert Central Research Institute for Field Crops, Turkey

Durum wheat is second important crop after bread wheat and it was grown as spring and winter type in Turkey. Rusts are the most important diseases limiting durum wheat production in Turkey. The aim of the study was determining of the resistance of the 232 Turkish winter durum wheat genotypes in preliminary yield trials developed by the Central Research Institute for Field Crops (CRIFC) to rusts.  For this purpose, adult plant and seedling test were conducted for yellow rust while only seedling test were conducted for leaf and stem rust. Evaluations were carried out at the research facilities of CRIFC at İkizce and Yenimahalle in Ankara in the 2014 season. For adult plant reactions; the genotypes were inoculated with local Pst populations (virulent on Yr2,6,7,8,9,25,27,Sd,Su,Avs). Stripe rust development on each entry were scored using the modified Cobb scale when the susceptible check cv. Little Club had reached 80S infection severity in June, 2014. Coefficients of infections were calculated and values below 20 were considered to be resistant. For seedling test; the seedling was inoculated with local Pgt (avirulent on Sr24, Sr26, Sr27, and Sr31), Pt (avirulent on Lr9, Lr19, Lr24, and Lr28) and Pst populations. Stripe, leaf and stem rust development on each entry were scored after 14 days with 0-4 and 0-9 scale for leaf-stem rust and yellow rust, respectively. In seedling stage, 141(65%), 41(18%), and 114 (49%) genotypes were resistant to local Pgt, Pt, and Pst populations, respectively. In adult plant test, 21 (9%) genotypes were resistant to Pst.  The resistance genotypes to stem, leaf, and stripe rust were determined with this research.

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Genetic characterization of slow rusting resistance to leaf rust in durum wheat cv. Bairds

Lan International Maize and Wheat Improvement Center (CIMMYT), México

The CIMMYT durum Bairds is susceptible to leaf rust (LR) at the seedling stage but shows an adequate level of slow rusting adult plant resistance (APR) in Mexican field environments. A recombinant inbred line (RIL) population developed from a cross of Bairds and the susceptible parent Atred#2 was phenotyped for LR response at Ciudad Obregon, Mexico, during 2013, 2014 and 2015 under artificial epidemics created with Pt race BBG/BP. Genetic analysis indicated that 3-4 additive genes conferred LR resistance. The RILs and parents were also genotyped with the 50K diversity arrays technology (DArT) sequence system and 93 SSR markers. A genetic map comprising 1,150 markers was used to map the resistance loci. Inclusive composite interval mapping analysis detected four quantitative trait loci (QTL) on chromosomes 1BL, 2BC (centromere region), 5BL and 6BL. These QTL, designated as QLr.cim-1BL, QLr.cim-2BC, QLr.cim-5BL and QLr.cim-6BL, explained 20.1-60.7%, 6.4-13.1%, 4.3-11.2%, and 7.1-28.0%, respectively, of the variation in leaf rust severity. QLr.cim-1BL was close to the previously reported APR gene Lr46, whereas QLr.cim-6BL, detected in all three seasons, is a new resistance locus in durum wheat. The four QTL combined showed a significant additive effect on resistance with a disease severity of 18-20%, whereas RILs carrying the individual QTL showed mean leaf rust severities ranging from 56 to 98%. Three QTL, except for QLr.cim-2BC, were derived from Bairds. The final LR severity of Bairds ranged from 15-25% across three years. This cultivar can be used as a source for complex APR in durum wheat breeding.

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

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

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The reactions of winter wheat stem rust resistance sources to stem, leaf and stripe rusts in 2014

Mert The Central Research Institute for Field Crops, Turkey

Stem rust still remains an important threat to wheat with new races such as Ug99. In 2012 main season, some genotypes developed by Central Research Institute for Field Crops were sent to Kenya for screening to Ug99 and WWSRRN (winter wheat stem rust resistance nursery) was organized with resistant genotypes according to result. Addition to Ug99, the resistances to local stem rust, leaf rust and yellow rust races are important.  The aim of this study was  to determine reactions of 99 genotypes in WWSRRN  to local rust population in the seedling stage (for PSt, Pgt and Pt) and adult plant stage (for Pst and Pgt) at the research facilities of CRIFC in Ankara and Kastamonu (stem rust) during 2014 season. For adult plant test; the genotypes were inoculated with local Pst populations (virulent on Yr2,6,7,8,9,25,27,Sd,Su,Avs) and local Pgt populations (avirulent on Sr24, Sr26, Sr27, and Sr31). Stripe and stem rust development on each entry were scored using the modified Cobb scale when the susceptible check Little Club had reached 80S infection severity in June and August 2014, respectively. Coefficients of infections were calculated and values below 20 were considered to be resistant. For seedling test; the seedling was inoculated with local Pgt, Pt (avirulent on Lr9, Lr19, Lr24, and Lr28) and Pst populations. Stripe, leaf and stem rust development on each entry were scored after 14 days with 0-4 and 0-9 scale for leaf-stem rust and yellow rust, respectively. Thirty seven (37%) (seedling) genotypes and 39 (39%) (adult stage)  genotypes were resistant to local Pgt, 35 (35%) (seedling) were resistant to the local Pt, and 55 (56%) (seedling) and 59 (60%) (adult stage) genotypes were resistant to the local Pst populations. The resistance sources to stem, leaf, and stripe rust were determined with this research.

 

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Genetic analysis of stripe rust resistance in a common wheat landrace AWCC275

Wells The University of Sydney Plant Breeding Institute Cobbitty, Faculty of Agriculture and Environment, Australia

Improvement of stripe rust resistance is one of the main aims of wheat breeding programs worldwide. Progress is dependent on the availability of genetically diverse and widely effective sources of resistance. This study focuses on genetic analysis of stripe rust resistance in landrace accession AWCC275 from the Watkins Collection. AWCC275 was scored resistant to moderately resistant under field conditions during three crop seasons and showed an intermediate seedling response (infection type 2C). AWCC275 was crossed with the susceptible genotype Avocet S and a population of 76 F3 families was generated. Twenty seedlings of each family were tested at the seedling stage with Puccinia striiformis f. sp. tritici pathotype 134 E16A+,Yr17+,Yr27+ under greenhouse conditions. Sixteen lines were homozygous resistant (HR), 43 segregated and 17 were homozygous susceptible (HS). Chi-squared analysis (?21:2:1 =1.34, non-significant at P=0.05 and 2 df) indicated segregation at a single locus. HR and HS lines were submitted for selective genotyping using the 90K SNP platform. The population is currently being advanced to F6 for detailed molecular mapping and the resistance gene is being backcrossed to three Australian wheat cultivars.

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Contig reduction in genomic assembly of Pst isolates from Western Canada

Laroche Agriculture and Agri-Food Canada, Lethbridge Research Centre, Canada

We earlier assembled the genomes of Pst isolates collected in western Canada using assembly of Illumina paired-end sequences. Two isolates, LSW3_2012_SP2 and SWS484_SPF, were assembled with ?15,150 and ?11,700 contigs each when compared to references North American PST-78 and Chinese CYR32, respectively. In order to reduce the number of contigs and therefore obtain a longer display of contiguous genes, we used the PacBio and Illumina Mate Pair (MP) technologies to achieve that goal using the two isolates. We had to modify our current protocol for DNA isolation from Pst spores to obtain DNA fragments of ?35 Kb suitable for construction of large insert genomic sequencing libraries. Libraries of 8-10 Kb and 3.5-6 Kb were used for PacBio and Illumina MP analyses, respectively. We obtained a 26x coverage of the Pst genome with the PacBio results with an mean size of 7,400 bp and 6,500 bp for the two libraries, and a 190x coverage with the Illumina MP sequencing information. We are using the Ray assembler with the datasets and the 50x Illumina paired end sequencing information from previously independently associated isolates LSW3_2012_SP2 and SWS484_SPF. The quality of our assembly will be compared to the contigs and supercontigs available for the reference isolates PST-78 and CYR32. These results will also enable us to establish the physical relationship among isolate-specific genes. Finally, the impact of the large insert libraries on the proportion of short paired-end unassembled reads will be discussed as it was 78% and 50% for LSW3_2012_SP2 and SWS484_SPF, respectively, after assembly of 100 bp paired-end reads.

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

Hansen Aarhus University, Denmark

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.

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Yr26-virulent Puccinia striiformis f.sp. tritici pathotypes in China are genetically diverse

Zhan State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, P.R. China

A Pst pathotype group named V26, virulent to wheat lines possessing Yr26 (=Yr24) has become the third most frequent group in China after races CYR32 and CYR33. Twenty four near-isogenic lines (NILs) and 19 Chinese differentials were used to identify the avirulence/virulence spectra of 36 Yr26-virulent isolates from four provinces (Qinghai, Gansu, Sichuan and Ningxia). Eight races were identified when tested on the NIL set, and 7 races were identified on the Chinese set. There was no relationship with province of origin. Three races identified on the NILs occurred at relatively high frequencies (23, 3, and 3 isolates). Virulence differences existed for Yr1, Yr4, Yr6, Yr9, Yr17, Yr25, Yr32, YrSp, and YrTr1. Among the 7 races identified on the Chinese differentials, one (CYR32 + Yr26 virulence) was represented by 13 isolates and another (CYR33 + Yr26 virulence) included 15 isolates. Among the entire group there were virulence differences on Trigo-Eureka (Yr6+), Lovrin 13 (Yr9+), Kangyin 655, Fengchan 3 (Yr1+), Lovrin 10 (Yr9+), and Hybrid 46 (Yr4+). All isolates were avirulent on Zhong 4 and T. spelta. Using 18 polymorphic simple sequence repeat (SSR) markers, we identified 35 genotypes clustered into two molecular groups (MGs) at a similarity coefficient level of 0.70. SSR analysis also indicated a high level of recombination within the V26 group. The considerable diversity indicates a threat not only to cultivars carrying Yr26, but also to other currently resistant materials.

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