All BGRI Abstracts

Displaying 21 - 30 of 196 records | 3 of 20 pages

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. pseudohordeiPsph) 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.

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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.

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Molecular mapping of resistance to the Pgt race Ug99 group in spring wheat landrace PI 177906

BGRI 2015 Poster Abstract
Babiker USDA-ARS, Small Grains and Potato Germplasm Research Unit, USA
View babiker.pdf (941.79 KB)

Wheat landrace PI 177906 has seedling and field resistance to Pgt races TTKSK and TTKST. From a cross between PI 177906 and LMPG-6, 138 doubled haploid (DH) lines and 144 recombinant inbred lines (RILs) were developed and tested for seedling resistance to Pgt race TTKSK. Goodness-of-fit tests from both populations indicated that two dominant genes in PI 177906 conditioned resistance to race TTKSK. Parents and the 138 DH lines were evaluated in the field in two experiments in Kenya; one in the main season and one in the off-season. The 90K wheat iSelect SNP genotyping platform was used to genotype the parents and DH lines and data were used to construct a genetic linkage map. Two loci for seedling resistance were mapped to chromosomes 2BL and 4BL. Two major QTL for field resistance mapped to the same regions, a 14.4 cM interval on 2BL and an 8.5 cM interval on 4BL. The QTL on 2BL and 4BL explained, respectively, 31.9-32.3% and 18.2-19.1% of the variation in the off-season and 28.3-30.4% and 5.4-6.5% of the variation in the main-season. Based on the mapping results, race specificity, and the seedling infection types, the resistance gene in 2BL could be Sr28, whereas the gene on chromosome 4BL could be novel. The mapping results will be verified in the RIL population using the flanking SNP markers in KASP assays.

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Rapid detection of micro-RNAs associated with APR to rust pathogens in wheat

BGRI 2015 Poster Abstract
Singh The University of Queensland, Queensland Alliance for Agriculture and Food Innovation, Australia

The identification of R-genes using traditional map-based approaches is a long, laborious process, not to mention the time required for subsequent development of cultivars incorporating the new resistances. Breeders seek to reduce the length of breeding cycles, and researchers require new tools to accelerate discovery and understanding of mechanisms associated with durable resistance, especially adult plant resistance (APR). A new method for rapid generation advancement, known as ‘speed breeding’, significantly reduces the length of breeding cycles, provide increased recombination during line development and enable selection in early generations. The speed breeding protocol uses controlled temperature regimes and 24h light to accelerate plant growth and development. Phenotyping methods adapted for use in the speed breeding system permit year-round evaluation of APR to rust pathogens within 5 weeks from time of sowing. RNA sequencing (RNA-Seq) technology has revolutionized gene expression profiling in plants. We previously used RNAseq to identify novel transcripts and miRNAs associated with seedling resistance (Lr28) leading to identification of transcription factors and miRNA families (e.g. miR36, miR37 and miR39) involved in signalling and defense response (Kumar et al. J. Nuc. Acids 2014:570176). In this study we report the application of speed breeding and RNAseq technologies for the purpose of rapidly identifying transcripts and miRNA associated with APR. Wheat landraces harbouring novel sources of resistance were grown under speed breeding conditions and sampled for RNA at key growth stages, before and after inoculation, which enabled discovery of differentially expressed miRNAs. Our next steps are aimed at validating these genetic factors associated with APR in order to better understand the signalling pathways and deliver tools to assist the assembly of robust wheat cultivars for the future.

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Reactions of spring wheat genotypes in crossing block nursery to stem, leaf, and stripe rust

BGRI 2015 Poster Abstract
Mert The Central Research Institute for Field Crops, Turkey

Rusts (Puccinia spp.) are the most significant disease affecting wheat yield and quality in Turkey. Knowing the resistance status of wheat genotypes in crossing program is an important issue for breeding programs. The aim of the study was to determine of the resistance of the 106 wheat genotypes consisting of Crossing Block Spring Wheat (CBSW) nursery developed by the International Winter Wheat Improved Project (IWWIP). 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 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, thirty nine (37%), 47 (44%), and 20 (19%) genotypes were resistant to local Pgt, Pt, and Pst populations, respectively. In adult plant test, 46 (43%) genotypes were resistant to Pst.  The resistance genotypes to stem, leaf, and stripe rust were determined with this research.

 

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The Stubbs Pst Culture Collection: Recovery, avirulence/virulence phenotyping and past population structure at a global scale

BGRI 2015 Poster Abstract
Thach Department of Agroecology, Aarhus University, Denmark

The "Stubbs Collection", began in 1956 by the late Dutch plant pathologist R.W. Stubbs, refers to a unique historic collection of urediniospore samples of Puccinia striiformis that had been stored in liquid nitrogen for decades. Since 2010 the collection has been maintained by the Global Rust Reference Center (GRRC) in Denmark. Part of the collection is now being in a study of past pathogen diversity. A subset of samples collected between 1958 and 1991 from 35 countries was investigated to assess recovery rate, race identity, and previously undetected virulences. A new method for recovery using an airbrush sprayer and NovecTM 7100 fluid as dispersal agent in inoculating host plants was highly successful, resulting in a 96% recovery from 231 isolates. Phenotyping on the World and European differential host sets and additional wheat genotypes revealed 181 apparently uniform isolates, of which race identities were confirmed for 102. Race identities were updated for additional isolates based on improved resolution due to updated and more informative differential lines. Additional virulences corresponding to Yr17, Yr25, and Yr27 were added, as these were not assayed earlier. The past population structure was investigated by genotyping 212 isolates using 19 multilocus microsatellites. Seven distinct populations were detected, including clonal populations and recombinant populations. These results were compared with recent studies and demonstrated an overall consistent population subdivision at the global scale with clear migration events between populations. The outcome of the study facilitates conclusions about long-term temporal dynamics and overall migration patterns within and among world-wide populations of Pst.

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Wheat stem rust effectors: Genomics and functional assay

BGRI 2015 Poster Abstract
Upadhyaya CSIRO Agriculture, Canberra, Australia

Puccinia graminis f. sp. tritici (Pgt) is one of the most destructive pathogens of wheat. Fungal secreted proteins termed effectors play an important role in modulating the host cellular environment and suppressing the plant defense response to enable fungal growth. They also become targets of plant resistance (R) proteins. We have taken a genomics approach to initially identify candidate effectors. We have built a draft genome for a founder Australian Pgt isolate of pathotype (pt.) 21-0 (collected in 1954) by next generation DNA sequencing. A combination of reference-based assembly using the genome of the previously sequenced North American Pgt isolate CDL 75-36-700-3 (p7a) and de novo assembly resulted in a 92 Mbp reference genome for Pgt isolate 21-0. This draft genome was subsequently used to build a pan-genome based on five Australian Pgt isolates. Transcriptomes from germinated urediniospores and haustoria were separately assembled for pt. 21-0 and comparison of gene expression profiles showed differential expression in ~10% of the genes in germinated urediniospores as well as haustoria. A total of 1,924 secreted proteins were predicted from the 21-0 transcriptome, of which 586 were classified as haustorial secreted proteins (HSPs). We are currently exploring effector gene expression during infection of wheat to reduce this candidate list based on a common expression profile identified for Avr genes in the flax rust fungus. Comparison of 21-0 with two presumed clonal field derivatives (collected in 1982 and 1984) that had evolved virulence on four additional resistance genes (Sr5, Sr11, Sr27, SrSatu) identified mutations in 13 HSP effector candidates. These candidate effectors are being assessed for recognition in wheat accessions with the corresponding R genes using a bacterial type three secretion delivery system based on an engineered Pseudomonas fluorescence strain (Upadhyaya NM et al. Mol Plant Microbe Interact 27:255-264).

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Introgression of genes for high grain protein content (Gpc-B1) and Lr24 into leading cultivars by marker assisted backcross breeding

BGRI 2015 Poster Abstract
Mishra Department of Genetics and Plant Breeding, Institute of Agricultural Sciences, Banaras Hindu University, India

A wheat genotype PBW343+Gpc-B1+LR24 containing the high grain protein content (GPC) gene Gpc-B1 linked to marker Xucw108 was used as the donor parent to transfer Gpc-B1 and Lr24 into Eastern Gangetic Plains (EGP) cv. HUW234 and HUW468 that were released in 1986 and 1999, respectively. The backcrossing program involved the following steps: (i) foreground selection, (ii) marker selection, and (iii) recovery of recipient parent genome. Grain protein contents were recorded for all selected plants from the BC2F2:3 generation. The dominant marker Xucw108 was used for foreground selection, and heterozygous plants were identified through progeny testing. For RPG recovery, both genotypic and phenotypic selection was used. Introgression of the high GPC gene into the recipient background without yield loss was completed in 5 years, starting from 2009-10 (F1) and completed in 2013-14 (BC2F5). A conventional selection program would take the same time to reach BC2F5 but ensuring the transfer of GPC would not not be possible. Ten selected single plants from the BC2F3:4 generation had comparable yields of the parents with 26% higher GPC than the recurrent parent HUW 234. Eight selected plants had comparable yields and 34% higher GPC than HUW 468. Multi-row progenies (BC2F4 and BC2F5) of each selected plant were evaluated in yield traits with the donor and recipient parents as controls during 2012-13 and 2013-14. Two lines based on each recurrent parent were identified with significantly higher GPC with no yield penalty. The study reinforced the belief that MAS in combination with phenotypic selection could be a useful strategy to develop high GPC genotypes without sacrificing grain yield. These lines will be submitted to national trial where MAS derived lines require only two years of testing compared to four years for conventionally bred lines.

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Targeting stem rust resistance genes Sr32 and Sr1644 for cloning by mutagenesis and sequence capture

BGRI 2015 Poster Abstract
Wulff John Innes Centre, UK

Resistance offers the best means of control of the cereal rusts, but must be strategically deployed so as to avoid exposure of single major genes, which have faltered so many times in the past. The pyramiding of multiple effective resistance genes is a strategy that has proven effective in a number of wheat production areas around the world. However, the process of incorporating multiple resistance genes into a single cultivar using standard breeding techniques is time consuming, laborious, and hampered by the problem of linkage drag. If a suite of effective resistance genes could be efficiently cloned and transferred into wheat as a cassette, it would accelerate the development of durably resistant varieties without the problem of linkage drag. Toward this end, we have developed a resistance gene cloning technology based on resistance gene enrichment sequencing (RenSeq) of EMS-derived mutant R gene alleles. As a proof of concept test, we successfully ‘re’-cloned the already characterized gene Sr33 and are now targeting the cloning of eight other effective resistance genes. For the identification of susceptible mutants for the cloning of Sr32 from Aegilops speltoides, we screened 1,109 M2 families with race TPMKC — as a surrogate for race TTKSK. Five susceptible M2 mutants were confirmed by progeny testing. These mutants were also susceptible to race TTKSK. For the population involving Sr1644 from Ae. sharonensis, 1,649 M2 families were screened, yielding 33 M2 families that appeared to segregate for susceptibility. Thirteen of 33 families were confirmed as bona fide susceptible mutants by progeny tests in the M3 generation. Identification of susceptible EMS mutants of Sr32 and Sr1644 suggests that the underlying resistance in these lines is conferred by single genes. We will report on progress to clone and characterize these genes using R gene exome capture and sequencing technology (RenSeq).

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Resistance to wheat stem rust in selected accessions of Iranian wheat landraces

BGRI 2015 Poster Abstract
Mojerlou Tarbiat Modares University of Tehran, Iran
View mojerlou.pdf (199.61 KB)

Stem rust is a potentially destructive fungal disease of wheat worldwide. In 1998 Pgt pathotype TTKSK virulent to Sr31 was detected in Uganda. The same pathotype was confirmed in Lorestan and Hamedan provinces of Iran in 2007. We used a derivative of race TTKSK to phenotype 62 Iranian wheat landraces (resistant to stripe rust in a previous study) at the seedling stage to this new pathotype (TTSSK). Twenty eight accessions were evaluated for the presence of resistance genes Sr2, Sr22, Sr24, Sr25, Sr26, Sr35, Sr36 and Srweb using SSR markers. None carried Sr2, Sr24 or Sr26, but the presence of Sr22, Sr25, Sr35 and Sr36 was indicated. Some susceptible landraces predicted to carry Sr2 by marker analysis require further investigation. To evaluate defense gene expression in compatible and incompatible stem rust interactions we sampled resistant and susceptible cultivars at 0, 12, 18, 24, 72 hours post-inoculation (hpi). ?-1,3 glucanase expression was studied using qGLU-S and qGLUU-AS primers and a real-time PCR step-one ABI machine, with ?-tubulin and EF1-? genes used as internal controls. In incompatible interactions defense gene expression was increased at 24 hpi, but in compatible interactions the highest level of expression occurred at 12 hpi and was significantly decreased at 18 hpi. The results revealed that expression of defense genes such as ?-1,3 glucanase was earlier in compatible than in incompatible interactions but the expression level was less in incompatible interactions. On the other hand, in susceptible genotypes the expression of defense genes increased immediately after inoculation and declined sharply after infection. In contrast defense gene expression in resistant genotypes began to increase after establishment of the pathogen.

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