Permanent Genetic Resources added to Molecular Ecology Resources Database 1 February 2013-31 March 2013

This article documents the addition of 142 microsatellite marker loci to the Molecular Ecology Resources database. Loci were developed for the following species: Agriophyllum squarrosum, Amazilia cyanocephala, Batillaria attramentaria, Fungal strain CTeY1 (Ascomycota), Gadopsis marmoratus, Juniperus phoenicea subsp. turbinata, Liriomyza sativae, Lupinus polyphyllus, Metschnikowia reukaufii, Puccinia striiformis and Xylocopa grisescens. These loci were cross-tested on the following species: Amazilia beryllina, Amazilia candida, Amazilia rutila, Amazilia tzacatl, Amazilia violiceps, Amazilia yucatanensis, Campylopterus curvipennis, Cynanthus sordidus, Hylocharis leucotis, Juniperus brevifolia, Juniperus cedrus, Juniperus osteosperma, Juniperus oxycedrus, Juniperus thurifera, Liriomyza bryoniae, Liriomyza chinensis, Liriomyza huidobrensis and Liriomyza trifolii. © 2013 John Wiley & Sons Ltd.Peer Reviewe

Transfer of rust resistance genes from Triticum species to common wheat

A programme aiming to transfer leaf rust resistance genes identified in a collection of wild Triticum species was initiated in 1993. In 2000, 25 promising backcross populations were available, 19 of which bred true for resistance. Seedlings of the above lines were tested with nine leaf rust, four stem rust and two stripe rust pathotypes endemic to South Africa. A subset of five lines in which resistance (derived from T. dicoccoides, T. sharonense, T. speltoides and T. peregrinum) appeared to be integrated on wheat chromosomes and six addition lines with added chromosomes from T. kotschyi, T. peregrinum, T. umbellulatum, T. macrochaetum and T. neglectum appeared to have wide spectrum resistances, and were retained. In several instances promising stem rust and/or stripe rust resistance genes were co-transferred with leaf rust resistance. The stripe rust resistance was also effective to four Australian pathotypes and appeared to be novel. Temporary gene designations were assigned to the resistance genes in four euploid derivatives.Articl

Transfer of rust resistance genes from Triticum species to common wheat

A programme aiming to transfer leaf rust resistance genes identified in a collection of wild Triticum species was initiated in 1993. In 2000, 25 promising backcross populations were available, 19 of which bred true for resistance. Seedlings of the above lines were tested with nine leaf rust, four stem rust and two stripe rust pathotypes endemic to South Africa. A subset of five lines in which resistance (derived from T. dicoccoides, T. sharonense, T. speltoides and T. peregrinum) appeared to be integrated on wheat chromosomes and six addition lines with added chromosomes from T. kotschyi, T. peregrinum, T. umbellulatum, T. macrochaetum and T. neglectum appeared to have wide spectrum resistances, and were retained. In several instances promising stem rust and/or stripe rust resistance genes were co-transferred with leaf rust resistance. The stripe rust resistance was also effective to four Australian pathotypes and appeared to be novel. Temporary gene designations were assigned to the resistance genes in four euploid derivatives.Articl

Molecular mapping as a tool for pre-emptive breeding for resistance to the exotic barley pathogen, Puccinia striiformis f. sp. hordei

Barley stripe rust (BSR), caused by Puccinia striiformis f. sp. hordei, has been a major disease problem to the barley industry worldwide that has not, to date, been detected in Australia. This paper describes the mapping of stripe rust resistance genes in Tallon/Kaputar (TK) and Arapiles/Franklin (AF) populations. The paper also reports on the usefulness of markers associated with alternative sources of resistance previously identified in the varieties Orca and Shyri in the USA. Stripe rust screening was conducted at the adult plant stage in Toluca, Mexico, for 2 years. Two major quantitative trait loci (QTLs) were found on chromosomes 2H and 5H in both populations. One region on chromosome 5H was highly significantly associated with resistance to stripe rust (R2 = 68% and 34% in TK and AF, respectively). The QTL on chromosome 2H accounted for 36% of the variation in TK and 10% of the variation in the AF population. These associations were consistent over both years. Further work will involve screening for additional markers in the target regions to identify polymorphism that can be used to select for multiple resistances in the absence of the pathogen

Molecular mapping as a tool for pre-emptive breeding for resistance to the exotic barley pathogen, Puccinia striiformis f. sp. hordei

Barley stripe rust (BSR), caused by Puccinia striiformis f. sp. hordei, has been a major disease problem to the barley industry worldwide that has not, to date, been detected in Australia. This paper describes the mapping of stripe rust resistance genes in Tallon/Kaputar (TK) and Arapiles/Franklin (AF) populations. The paper also reports on the usefulness of markers associated with alternative sources of resistance previously identified in the varieties Orca and Shyri in the USA. Stripe rust screening was conducted at the adult plant stage in Toluca, Mexico, for 2 years. Two major quantitative trait loci (QTLs) were found on chromosomes 2H and 5H in both populations. One region on chromosome 5H was highly significantly associated with resistance to stripe rust (R2 = 68% and 34% in TK and AF, respectively). The QTL on chromosome 2H accounted for 36% of the variation in TK and 10% of the variation in the AF population. These associations were consistent over both years. Further work will involve screening for additional markers in the target regions to identify polymorphism that can be used to select for multiple resistances in the absence of the pathogen

Fine scale genetic and physical mapping using interstitial deletion mutants of Lr34 /Yr18: a disease resistance locus effective against multiple pathogens in wheat

The Lr34/Yr18 locus has contributed to durable, non-race specific resistance against leaf rust (Puccinia triticina) and stripe rust (P. striiformis f. sp. tritici) in wheat (Triticum aestivum). Lr34/Yr18 also cosegregates with resistance to powdery mildew (Pm38) and a leaf tip necrosis phenotype (Ltn1). Using a high resolution mapping family from a cross between near-isogenic lines in the “Thatcher” background we demonstrated that Lr34/Yr18 also cosegregated with stem rust resistance in the field. Lr34/Yr18 probably interacts with unlinked genes to provide enhanced stem rust resistance in “Thatcher”. In view of the relatively low levels of DNA polymorphism reported in the Lr34/Yr18 region, gamma irradiation of the single chromosome substitution line, Lalbahadur(Parula7D) that carries Lr34/Yr18 was used to generate several mutant lines. Characterisation of the mutants revealed a range of highly informative genotypes, which included variable size deletions and an overlapping set of interstitial deletions. The mutants enabled a large number of wheat EST derived markers to be mapped and define a relatively small physical region on chromosome 7DS that carried Lr34/Yr18. Fine scale genetic mapping confirmed the physical mapping and identified a genetic interval of less than 0.5 cM, which contained Lr34/Yr18. Both rice and Brachypodium genome sequences provided useful information for fine mapping of ESTs in wheat. Gene order was more conserved between wheat and Brachypodium than with rice but these smaller grass genomes did not reveal sequence information that could be used to identify a candidate gene for rust resistance in wheat. We predict that Lr34/Yr18 is located within a large insertion in wheat not found at syntenic positions in Brachypodium and rice

Development of Sequence Tagged Site and Cleaved Amplified Polymorphic Sequence Markers for Wheat Stripe Rust Resistance Gene Yr5

The Yr5 gene confers resistance to all races of the wheat stripe rust pathogen [Puccinia striiformis Westend. f. sp. tritici Eriks. (P. s. tritici)] identified so far in the USA. Cosegregating resistance gene analog polymorphism (RGAP) markers for Yr5 are available but their use requires skills in polyacrylamide gel electrophoresis and may not be polymorphic across various varieties. To develop better markers to be used in marker-assisted selection for the Yr5 resistance, sequence tagged site (STS) primers were designed on the basis of the sequences of RGAP markers Xwgp-18 (AY167598) from the spring wheat (Triticum aestivum L.) 'Avocet Susceptible' (AVS) and Xwgp-17 (AY167597) from the Yr5 near isogenic line (NIL) in the AVS background carrying the Yr5 gene from T. aestivum subsp. spelta (L.) Thell. cv. Album (TSA). Three sets of STS markers (two codominant and one dominant) were developed to amplify a region including a polymorphic 6-base pairs (bp) insertion-deletion (indel). The cosegregation of the STS markers with Yr5 was confirmed with 114 BC 7:F3 lines developed from the cross between AVS and TSA. The STS markers worked well in five out of 17 non-Yr5 wheat varieties, but the remaining varieties had a similar size of fragment to the Yr5 marker. Because the codominant STS markers were based on a 6-bp indel, they could not be separated by agarose gel electrophoresis. Cleaved amplified polymorphic sequence (CAPS) markers were then developed on the basis of a DpnII restriction site that is present in all non-Yr5 varieties and absent in the Yr5 NIL. The CAPS markers for the Yr5 NIL and non-Yr5 varieties can be separated by agarose gel electrophoresis. The codominant STS markers are easier to score than the original RGAP markers. The CAPS markers are not only easier to score, but also can be used in crosses of an Yr5 donor with a much wider range of wheat germplasms. These markers should be valuable tools to accelerate the introgression of Yr5 into commercial cultivars and to combine Yr5 with other genes for durable resistance to stripe rust