The stem rust resistance gene SrTmp carried by Triumph 64 confers resistance to Pgt race TTKSK and other members of the Ug99 race group. While some previous studies have mapped resistance postulated to be SrTmp, none used Triumph 64 as a parent. The purpose of this study was to genetically map SrTmp with DNA markers using a DH population from LMPG/Triumph 64 and compare the map position of SrTmp to previously mapped Sr genes. The DH population was tested with Pgt race TTKSK at the seedling stage. A single gene conditioned resistance to TTKSK (n = 144; χ21:1 = 0.44, p = 0.50). SrTmp was mapped to the distal region of chromosome 6DS with SSR markers. The map location of SrTmp was similar to SrCad and Sr42, which likely represent the same gene. In a concurrent study SNP markers were developed to fine-map SrCad. SNP markers were identified and/or developed using a public SNP database (http://www.cerealsdb.uk.net) and sequence information from an Aegilops tauschii genome sequencing project. Further SNP markers were developed by using resistance gene analogs from chromosome 6D to BLAST exome capture sequences from a set of Canadian wheat cultivars followed by searching for unique SNPs found in SrCad carriers. These SNP markers were added to the map of SrTmp. The map positions of SrTmp and SrCad/Sr42 are very similar. While preliminary data show functional differences between SrTmp and SrCad/Sr42, further analysis is needed to determine whether these genes are allelic or closely linked.
Primary Author: Hiebert, Agriculture and Agri-Food Canada, Cereal Research Centre, Canada
Management of the cereal rusts currently relies on the use of fungicides and varietal resistance. Host resistance can be rapidly overcome by mutations in the pathogen population and for this reason virulence surveys are undertaken worldwide to give early warning on any changes. The UK Cereal Pathogen Virulence Survey (UKCPVS) was established in 1967 following an outbreak of yellow rust on the variety Rothwell Perdix. The UKCPVS currently monitors the wheat yellow rust and brown rust pathogen populations as well as the wheat and barley powdery mildew pathogen populations. A watching brief is maintained on barley yellow rust. In 2011 a new Pst race was detected; named the Warrior race after the variety on which it was first found. Initial tests on differential host lines suggested that the race was another stepwise mutation with an added virulence for Yr7 in addition to a combination of virulences to Yr6, Yr9, Yr17 and Yr32. Other characteristics of this race, however, suggested something different from previous race changes with an increase in telial production seen under field conditions. In addition, this new race was seen simultaneously in multiple locations throughout Europe (www.wheatrust.org) in contrast to the more gradual appearance of new variants seen previously. Subsequent genotypic analysis of isolates (Hubbard et al. 2015, Genome Biol. 16:23) demonstrated that the new race was an exotic incursion. Results presented at the meeting will summarize some of the key changes in the pathogen populations, such as the arrival of the Warrior Pst race in 2011 and the re-emergence of the Glasgow race of the brown rust pathogen in 2014.
Primary Author: Holdgate, NIAB, UK
A whole of industry, co-ordinated system for the assignment of reliable stripe rust, stem rust and leaf rust disease response ratings of current wheat cultivars and advanced breeding lines was developed to meet the needs of the Australian grains industry. Previously there was a lack of national consistency in ratings with each state independently publishing response ratings. However, privatisation of public wheat breeding during the early 2000s, recurrent stripe rust epidemics following a foreign pathotype incursion in 2002, and the dramatic increase in fungicide use provided the impetus to develop a consistent approach to assignment of ratings. Factors that became critical to the process were: 1) access to dedicated rust nurseries in diverse cereal production environments, 2) use of single seed sources for consistent variety identity, 3) control lines that provided consistent rust responses in field nurseries across regions, 4) a centralised repository of current and historical data (provided by the National Variety Trials program), and 5) pathotype identification (provided by the Australian Cereal Rust Control Program (ACRCP)). This system was subsequently documented by the Cereal Pathology Working Group (a sub-committee of the ACRCP consultative committee) and included a dispute resolution process. Currently, with GRDC funding, approximately 200 lines comprising current cultivars and advanced breeding lines, are assessed nationally in dedicated rust nurseries by members of the Working Group. Both current and historical data are reviewed annually by the Working Group with consensus rust responses developed and then scrutinised by wheat breeding companies prior to public release. This whole of industry system has improved timeliness, reliability and consistency of information with ratings used widely by Australian farmers to select cultivars to minimise losses due to rust and to plan appropriate chemical control strategies should resistance be inadequate.
Primary Author: Hollaway, Department of Economic Development, Jobs, Transport and Resources, Australia
MACS 3949 is a durum wheat variety developed at Agharkar Research Institute, Pune derived through selection method from 39th IDYN (CIMMYT). The variety was identified by 55th All India Wheat and Barley workshop CCS HAU, Hissar and subsequently notified by Central Sub Committee on Crop Standards, India. On the basis of mean of three years (2013-14, 2014-15 and 2015-16) data from All India coordinated experiment, grain yield of MACS 3949 (43.98 q/ha) was higher to all the checks Viz., NIDW 295 (39.70 q/ha) and UAS 428 (41.78 q/ha). Overall, MACS 3949 showed a yield advantage of about 10.78 % over NIDW 295 and 5.24 % over UAS 428. The important morphological traits of the variety described as, semi dwarf with average plant height around 81 (78-83) cm, medium sized strong waxy semi erect green leaves, parallel dense spikes with long spreading awns. Grains were amber colored, bold lustrous, semi hard, elliptical in shape with short brush, soft threshing at maturity and1000-grain weight was about 47 (42-53) gm. The variety has shown resistance to leaf rusts, in particularly the seedling resistance to race 77-complex of leaf rust, stem rust, leaf blight, powdery mildew, flag smut and karnal bunt under both natural and artificial screening conditions. It has high protein content (12.9 %), better nutritional quality (Zinc 40.6 ppm, Iron 38.6 ppm) with good milling quality (Test weight 81.4 kg/hl) and best cooking quality for pasta product having highest overall acceptability 7.25. The newly developed durum wheat variety MACS 3949 released for cultivation at Peninsular Zone in India, which is having rich source of nutritional pasta quality with high zinc and iron content will be a promising one for future potential of export at international market.
Primary Author: Honrao, Agharakar Research Institute Pune
In the Czech Republic all three rust species on wheat occur. Leaf rust (Puccinia triticina) can be found almost everywhere, and it can cause yield losses up to 40% mainly in warmer parts of the country in South Moravia.
Yellow rust, typical for cooler climate, occurred in relatively long time intervals. However in 2013 new pathotypes tolerating higher temperatures occurred and caused yield losses. In 2016 yellow rust incidence was lower, being still important in Moravia, where yellow rust occurred already in previous years.
Stem rust incidence was very rare in the last years. However in Germany, outbreaks and new pathotypes (e.g. Digalu) of stem rust in 2013 were recorded and comeback of stem rust to Central Europe can be expected.
Rust control consists of chemical control and especially of breeding for resistance, that aims at combined resistance to all three rusts. On the scale 9 high resistance, 1 high susceptibility average 4 year rating (2013-2016) of the tested cultivars was 6.4 for yellow rust, 5.7 for leaf rust and 6.2 for stem rust.
"Triple rust resistance" was recorded in spring wheat LOTTE and winter wheat line SG-S 1684 13, high resistance to yellow rust and stem rust in the cultivar Steffi. Resistance to all three rusts of 14 winter wheat cultivars and 12 breeding lines from the Plant Breeding Station-Stupice is summarized on separate tables and described in the text.
Primary Author: Horcicka, Research centre SELTON
Pathogens, whatever their types, develop at the expense of the nutrients generated by host and it is largely assumed that classical sources turn into sinks when colonized by pathogens. Sugar appears to be the major carbon and energy source transferred from the host to pathogens. Uptake, exchanges and competition for sugar, at biotrophic interfaces, are controlled by membrane transporters and their regulation patterns are essential in determining the outcome of plant-fungal interactions. However, mechanisms of transport and transporters involved in carbon partitioning between organisms are still poorly understood.
In this study, a wheat sugar transporter protein (STP) gene, TaSTP1, was cloned from a wheat-Puccinia striiformis f. sp. tritici (Pst) interaction cDNA library. Transcripts of TaSTP1 were up-regulated in wheat leaves that were infected by Pst or had experienced exogenous ABA and certain abiotic treatments. Heterologous mutant complementation in Saccharomyces cerevisiae revealed that TaSTP1 transports a broad-spectrum monosaccharides including glucose, fructose, mannose and galactose. Transient expression in Nicotiana benthamiana and Arabidopsis protoplasts suggested that TaSTP1 is localized in plasma membrane. Yeast two hybrid and bimolecular fluorescence complementation (BiFC) validated oligomerization of TaSTP1. Knocking down TaSTP1 using the barley stripe mosaic virus-induced gene silencing system reduced the susceptibility of wheat to the Pst virulent pathotype CYR31. Hyphal abnormality was significantly observed in VIGS plants. These results suggest that TaSTP1 may directly or indirectly participate in sugar transport in the wheat-Pst interactions and exert influence on suagr supply of Pst.
Primary Author: Huai, State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, Yangling
Trait and trait stability are important for wheat breeding. Our objectives were to assess the relative efficiency of genomic selection (GS) for various wheat traits and trait stability using four different models. Genotyping was conducted with a 90K SNP chip panel. SNP tagging was used to obtain a subset of 3,919 relatively independent markers for downstream analysis. Phenotyping was conducted on a population consisting of 273 lines, from seven different soft red winter wheat breeding programs in the U.S.A. Eberhart and Russells’ regression and additive main effects and multiplicative interaction (AMMI) models were used to assess trait stability. GS accuracy (r) was assessed for ridge regression best linear unbiased prediction (rr-BLUP), Bayesian ridge regression (BRR), reproducing kernel hilbert space (RKHS), and elastic net (EN). Across all models, GS produced a wide range of accuracies for trait stability (0.1 to 0.65) that varied by trait and stability method. Accuracy was 0.35 for yield and 0.44 for yield stability using AMMI, indicating the viability of GS in selecting lines with both high and stable yield. Our findings lay the foundation for wheat breeding programs in northeastern U.S.A. to implement GS. It also provides useful information for wheat rust researchers: as phenotypic selection for rust resistance can be both expensive and time consuming and rapid evolution of rust pathogens require an emphasis on durable resistance controlled by multiple genes, the GS approach applicable for complex traits thus has potential to achieve higher gains per unit time than traditional breeding for rust resistance.
Primary Author: Huang, Horticulture and Crop Science, the Ohio State University, Ohio Agricultural Research and Development Center, USA
Stripe rust, caused by Puccinia striiformis tritici (Pst), continues its evolution towards virulence to race-specific resistance genes. Identification of Mexican Pst isolates MEX16-03 and MEX16.04 that changed infection types of Yr10 testers from 1 to 9 and for Yr24 (=Yr26) testers from 3 to 9 indicated that a mutation for virulence to these resistance genes has occurred in a predominant race detected in 2014 and maintained at CIMMYT as MEX14.191 and at INIFAP as CMEX14.25. Isolate MEX14.191 was responsible for the susceptibility of popular varieties Nana F2007 and Luminaria F2014 grown in central Mexican highlands. Isolate MEX16.04 has the following avirulence/virulence formula: Yr1, 5, 15, SP/Yr2, 3, 6, 7, 8, 9, 10, (17), 24, 26, 27, 28, 31, 32 using the Avocet near-isolines and other known testers. Virulence to Yr10 and Yr24 (=Yr26) were also confirmed by testing seedlings of cultivars Moro (Yr10), Chuanmai 42, and Neimai 836 (Yr24). Seedling tests carried on 200 bread wheat, 550 durum, and 460 synthetic hexaploid wheats with their respective durum parents from CIMMYT collection indicated that MEX16.03 and MEX16.04 do not represent a major threat because a majority of the lines remained resistant to these isolates. However, it is worth mentioning that durum cultivars, such as Khofa, Desert King, Anatoly, Movas, and Llareta INIA, and 10 primary synthetic hexaploid or synthetic-derived bread wheats that were resistant to MEX14.191 became susceptible to MEX16.03 and MEX16.04. Our results indicate that resistance gene Yr10 was absent and Yr24 occurred in low frequency in CIMMYT bread wheat germplasm. A majority of CIMMYT durum wheat possibly carried Yr24 in combination with other effective gene(s).
Primary Author: Huerta-Espino, INIFAP, Mexico
Yellow (stripe) rust continues to be an important disease of wheat in the irrigated EL Bajio region and northwestern Mexico, and in the High Plateau of Central Mexico. Isolate MEX 96.11, virulent to race-specific resistance genes Yr2, Yr3, Yr6, Yr7, Yr9 and Yr27, represented the most prevalent Pst race until 2001 and evolution of new virulences was slow. Several additional R-genes, including a gene in Pollmer triticale, are now defeated. The aggressive Pst race with Yr8 virulence, first detected in the United States in 2000, not only became widespread in Mexico by 2003 but continued to evolve at a more rapid rate with virulence to Yr1 occurring in 2003. However these races did not cause crop losses other than increased levels of head infections in some cultivars. Variants with virulences to Yr17 and Yr31 were detected in 2007 and 2008, respectively. These resistance genes are known to occur in some wheat varieties and breeding materials. 2010 disease data from trap nurseries that included the Avocet isolines and other varieties indicated the existence of virulence for Yr1, 2 (Siete Cerros), 3 (Tatara), 6, 7, 8, 9, 17, 27 and 31 (Rebeca F2000) in different Pst isolates. During the 2014 crop season, an epidemic occurred in farm fields and samples were collected and analyzed in greenhouse tests. Virulence combination V2, 3, 6, 7, 8, 9, 17, 27 and 31 first identified and represented in isolates CEVAMEX14.25 and MEX 14.141, and a similar isolate MEX14.146 virulent to Yr1 were the most frequent. These new virulence combinations caused yield losses in cultivar Nana F2007 grown in the Mexican highlands and Luminaria F2012, released for the irrigated areas of Bajio. Our results indicate a continuing evolution and accumulation of virulences in the aggressive Pst lineage. Determination of the defeated genes in Nana F2007 and Luminaria F2012 is underway.
Primary Author: Huerta-Espino, Campo Experimental Valle de México INIFAP, México
Stem rust, caused by Puccinia graminis f. sp. tritici, is a highly destructive fungal disease of wheat. This pathogen has been effectively controlled in western Canada through resistance since the 1950s. In 1999, a new highly virulent race of stem rust was identified in Uganda. The new strain, named “Ug99”, was given the North American race designation TTKSK. In situ screening has demonstrated that approximately 75% of Canadian wheat cultivars are susceptible to this new race of stem rust. Fortunately, two cultivars, Peace and AC Cadillac, were highly resistant to Ug99. A doubled haploid population was generated from the cross: RL6071/Peace, where RL6071 was the stem rust susceptible parent. In 2008, 189 DH lines from this population were evaluated for response to Ug99 in Kenya. RL6071 and Peace were rated: 80 S and 5 R, respectively. Disease ratings of the DH lines, ranged from 80 S to 1 R. Mendelian evaluation of the stem rust scores indicated a two-gene model (X2=5.51; 0.25<P<0.10; d.f.=3) of inheritance. Peace has the positive allele for the diagnostic Lr34 DNA marker (csLVMS1) published by Spielmeyer et al. (2008). It is believed that Peace carries Lr34 and that this gene may be one of the genes responsible for Ug99 resistance in this cultivar. Molecular mapping of the Ug99 resistance in cultivar Peace is underway.
Primary Author: Humphreys, Agriculture and Agri-Food Canada, Cereal Research Centre, Canada