All BGRI Abstracts

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Up scaling seed of Ug99 resistant wheat varieties to ensure protection against stem rust in Pakistan

Hussain International Maize and Wheat Improvement Center (CIMMYT) Pakistan Office

With ongoing threats of rust from both internal and international sources it has become a priority at CIMMYT and for Pakistan national programs to accelerate the rate of seed increase and to popularize new Pgt race Ug99 resistant varieties to avert future disasters. Seed of Ug99 resistant varieties NARC-11, Pak-2013, Dharabi-2011 and BARS-09 was produced under the Wheat Productivity Enhancement Program (WPEP). The country-wide participatory approach involves a partnership of farmers, seed companies and research institutes. In 2014 16,020 and 6,085 kg of seed of NARC-11 and Pak-13, respectively, were distributed all over the country, including Azad Jammu Kashmir and Gilgit-Baltistan. Comparative yields across Pakistan show that the rust resistant varieties are equal, or superior, to current stem rust susceptible varieties grown by farmers. Deployment and use of these varieties by farmers in Balochistan will have a significant impact not only on productivity, but may also avert the consequences of possible introduction of race Ug99.

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Leaf rust on high yielding winter wheats in Chile

Madariaga National Institute of Agricultural Research [INIA], Chile

The physical environment and farming system in Chile are conducive to high yields from winter/alternate wheat cultivars. The national average yields for 2012-2014 were 6.5 t/ha for pasta wheat and 5.3 t/ha for bread wheat grown on 19,000 and 239,000 ha, respectively. The most efficient farmers obtain averages of 8-9 t/ha, and experimental plots at southern INIA sites are as high as 14 t/ha. The most important diseases are Septoria leaf blotch, stripe rust, powdery mildew, and BYDV. Recent increases of leaf rust on winter cultivars from near non-existence to the level of a major threat are a concern. Wheat cultivars such as Bicentenario INIA showed yield increases of 31.7% to reach 12.4 t/ha yield when sprayed twice with a mixture of strobilurin and triazol compared to 9.4 t/ha for the unsprayed control. Susceptible winter cultivars being introduced by private companies require complete chemical protection. In order to understand the virulences present in the pathogen population the Thatcher NILs were grown in 2014/15 under non-inoculated conditions in central [Chillan] and southern [Osorno] Chile. The Morocco check showed 100S, Thatcher 60S, TcLr1 40S, TcLr2b 30S, TcLr2c 40S, TcLr3a 30S, TcLr3ka 20S, TcLr3bg 30S, TcLr9 20S, TcLr10 60S, TcLr11 80S, TcLr12 60S, TcLr13 70S, TcLr14a 70S, TcLr15 50S, TcLr16 60S, TcLr17a 30S, TcLr18 20MR, TcLr19 0, TcLr20 30S, TcLr21 0, TcLr22a 0, TcLr23 70S, TcLr24 60S, TcLr25 0, TcLr26 60S, Lr27+31 80S, TcLr28 10MR, TcLr29 40MS, TcLr30 60S, TcLr32 70S, TcLr33 60S, TcLr34 70S, TcLr35 10MR–MS, Lr36 0, and TcLr37 0. The most significant differences (>40%) in response between the two locations were for TcLr2b, TcLr2c, TcLr11 and TcLr33. The Cereal Disease Laboratory (U.S.A.) tested 68 isolates from 55 samples from 2012/13 and identified 14 races, including one Triticum turgidum race (BBBQJ 26%). Significant breeding efforts are currently underway to address the leaf rust problem in Chile.

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SNP discovery and genotyping of wheat-Dasypyrum villosum disomic addition lines by genotyping-by-sequencing (GBS) to facilitate identification and introgression of novel stem rust resistance genes

Ando Department of Crop and Soil Sciences, Washington State University, USA

Most accessions of Dasypyrum villosum (2n = 2x = 14), a tertiary gene pool of wheat, were resistant in previous tests with a collection of Pgt races, including TTKSK. In order to transfer novel resistance genes with minimum linkage drag into wheat, chromosome-specific markers linked to the resistance loci would be useful. However, the currently available SNP and sequence information for D. villosum is very limited. Hence, developing SNP markers and genotyping D. villosum will aid in transferring stem rust resistance genes to wheat. We used genotyping-by-sequencing (GBS) to sequence a complete set of Chinese Spring (CS)-D. villosum addition lines (1V#3 to 7V#3) as well as CS and several D. villosum accessions to map D. villosum SNPs on each chromosome. We have also produced TTKSK-resistant CS-D. villosum amphiploids using other D. villosum accessions assuming they could carry different stem rust resistance genes.

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Rust reactions of wheat lines developed by another culture

Akan Central Research Institute for Field Crops, Turkey

Turkey is an important producer of bread wheat. Fungal diseases, including the rusts, limit production. Resistant varieties are the main strategy for rust control. In this study 33 doubled haploid lines developed by anther culture and 9 standard cultivars were evaluated for seedling (YR, LR, and SR) and adult plant reactions (YR) to rusts at the Central Research Institute for Field Crops at Yenimahalle and Ikızce in 2014. For adult plant reactions the genotypes were inoculated with local Pst populations (virulent on differentials with Yr2 Yr6, Yr7, Yr8, Yr9, Yr25, Yr27, YrSd, YrSu, and YrA). Stripe rust development on each entry was scored on the modified Cobb scale when the susceptible check Little Club reached 80S disease severity in June 2014. Coefficients of infection below 20 were considered to be resistant. Seedlings were inoculated with local Pgt (avirulent on differentials with Sr24, Sr26, Sr27 and Sr31), Pt (avirulent on differentials with Lr9, Lr19, Lr24 and Lr28) and the Pst population. Seedling reactions were recorded 14 days post inoculation on either 0-4 (SR and LR) or 0-9 (YR) scales. Thirteen (33%), 2 (5%) and 9 (23%) genotypes were resistant to SR, LR and YR, respectively. Fifteen (38%) genotypes were resistant to stripe rust at the adult stage.

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Current status of wheat rust and its management approaches in Nepal

Mahto Plant Pathology Division, Nepal Agricultural Research Council (NARC), Nepal

Wheat is one of the three most important food crops of Nepal for which rusts (Puccinia triticina, P.striiformis and P.graminis) are major biotic stresses. Leaf rust is widespread and causes 14-20% yield losses and speculated that P.triticina over summer on self-sown wheat in hills of Nepal. Twenty two different pathotypes of P.triticina have been recorded while thirteen leaf rust resistant genes (Lr1, Lr3, Lr10, Lr13, Lr14a, Lr16, Lr17, Lr19, Lr23, Lr26, Lr27, Lr31 and Lr34) either singly or in combinations, impart resistance to wheat genotypes in Nepal. Yellow rust is also a major disease in mid and lower hills, river basin and valleys, causing 30-80 % grain yield losses. Twenty-nine pathotypes of P.striiformis have been recorded till now in Nepal while nine Yr genes (Yr2, Yr2 KSA, YrA, Yr6, Yr7, Yr9, Yr27, GA, and SU) have been postulated. Stem rust is a minor and sporadic disease in central, western, mid-western region late in the season. Nine Sr genes (Sr2, Sr5, Sr7b, Sr8, Sr8a, Sr9b, Sr11, Sr25 and Sr31) have been characterized. Vijay was the first Ug99 resistant wheat variety released for cultivation. Previous experiences show that Nepal served as a focal point of wheat rusts for further spread in the Gangetic plains of India due to presence of more than 25 species of Berberis in hills of Nepal. Efforts are underway to survey rusts infection on Berberis spp. Use of Tilt (Propiconazole), Triadimefon (Bayleton) and Indar (RH-124) was found effective to reduce leaf rust as well as foliar blight. Cultivation of resistant varieties in Nepal not only reduces rust severity in this country but also minimizes crop losses in other neighboring countries especially India. This demands the need for regional collaboration in South Asia to combat wheat rusts.

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Development of wheat lines with complex resistance to rusts and Fusarium head blight

Mare Department of Plant Sciences, University of the Free State, South Africa
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Wheat is an economically important food crop in South Africa and production is influenced by a number of diseases caused by fungal pathogens, especially leaf rust, stem rust, stripe rust and Fusarium head blight. The aim of the study is to combine durable rust and FHB resistances into a single wheat line with a high percentage of cv. Krokodil genetic background. Two sets of wheat lines respectively resistant to the three rusts or FHB were developed from different breeding programs at the University of the Free State. These lines were used as parents to combine durable rust and FHB resistance genes/QTL into a single line. Three of the best rust resistant lines were selected as female parents containing rust resistance genes/QTL Lr19, Lr34/Yr18/Sr57, Sr2, Sr26, Sr39 and QYr.sgi-2B.1. FHB resistant BC2F2 and BC2F6 lines were selected as male parents; these lines contained different combinations of Fhb1, Qfhs.ifa-5A-1 and Qfhs.ifa-5A-2. All parental lines were evaluated using molecular markers to confirm the presence of the expected genes/QTL. More than 100 crosses were made between the rust and FHB resistant parents. Since the parents were not homozygous for all markers, leaf material from six-week-old F1 seedlings was collected for marker-assisted selection and to identify the best plants with combined rust and FHB resistances. The best selected lines will be use to develop a backcross population using cv. Krokodil as the recurrent parent. Lines with different combinations of resistance genes/QTL are currently being evaluated in the field to confirm the presence of these genes/QTL.

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Saturation of the Yr34 region of wheat chromosome 5AL to identify closely linked SNP markers

Qureshi The University of Sydney Plant Breeding Institute, Australia

Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici (Pst), is a major threat to global food security. Although stripe rust was detected for the first time in Eastern Australia in 1979, Western Australia (WA) remained free from stripe rust until 2002. The Pst incursion in WA was pathotyped as 134 E16A+ and differed from the most widely virulent pre-2002 group by combined virulence to Yr8 and Yr9 and avirulence for Yr3 and Yr4. An advanced breeding line, WAWHT2046, expressed resistant to moderately resistant (R-MR) response to 134 E16A+ under field conditions, and infection type (IT) 23C - 3C at the seedling stage. The resistance gene Yr34 that controlled stripe rust in WAWHT2046 was 12.2 cM distal to the awn inhibitor B1 in chromosome 5AL (Bariana et al. 2006; Theor Appl Genet 112:1143-1148) based on a Carnamah/WAWHT2046 doubled haploid (DH) population. The present investigation was planned to identify SNP markers closely linked with Yr34. Eight homozygous resistant and eight homozygous susceptible lines from the Carnamah/WAWHT2046 DH population were used for selective genotyping using SNP markers. Twenty four SNP markers were associated with resistance. Kompetitive allele-specific primers (KASP) were designed and SNP markers were genotyped on the DH population. SNP marker IWB80451 mapped 1.7 cM proximal to Yr34.

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Complementary resistance genes in wheat selection Avocet R conferring resistance to stripe rust

Dracatos The University of Sydney, Plant Breeding Institute, Australia

This study reports the inheritance and genetic mapping of YrA seedling resistance to stripe rust in a resistant selection of the Australian spring wheat variety Avocet (AUS20601). Genetic analysis was performed on F2 and F3 generation families derived from crosses between wheat genotypes previously reported to carry the YrA resistance and lines that lack the YrA resistance phenotype. Seedling tests with two Pst pathotypes (104 E137 A- and 108 E141 A-) avirulent with respect to YrA confirmed that the resistance was inherited as two complementary dominant genes. Ninety-two doubled haploid (DH) lines derived from a cross between the Australian cv. Teal (seedling-susceptible) and Avocet R were used to confirm the mode of inheritance of YrA and to develop a DArT-Seq genetic map to locate the components of the YrA resistance. Marker-trait association analysis based on 9,035 DArT-Seq loci mapped the two genes to chromosomes 3DL and 5BL. F2 populations derived from intercrosses of seedling susceptible DH lines that carried each gene (based on marker genotype) reproduced the YrA phenotype and specificity, confirming the complementary resistance gene model. The YrA resistance component loci were designated Yr73 (3DL) and Yr74 (5BL). Candidate single gene reference stocks will be permanently accessioned following cytological analysis to avoid a T5B-7B translocation in Teal relative to Avocet and Chinese Spring.

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Phenotypic and genotypic analysis of stripe rust, leaf rust and stem rust resistance genes in Tajik wheat varieties

Rahmatov Tajik Agrarian University, 146, Tajikistan

The objective of this study was to characterize seedling and adult plant resistance to all three rusts in a set of 40 bread wheat varieties currently cultivated in Tajikistan. Gene postulation based on multi-pathotype seedling test data and adult plant responses identified Yr2, Yr9, Yr17 and Yr27; Lr10 and Lr26; and Sr5, Sr6, Sr10, Sr11, Sr31 and Sr38. The effects of slow rusting, adult plant, pleiotropic resistance genes Lr34/Yr18/Sr57 and Yr30/Lr27/Sr2 were observed in the field and confirmed with molecular markers. Furthermore, molecular markers diagnostic for Yr9/Lr26/Sr31 and Yr17/Lr37/Sr38 were assessed on all varieties. Genes Lr34/Yr18/Sr57, Yr9/Lr26/Sr31 and Yr27 were identified in varieties Sarvar, Vahdat, Oriyon, Isfara, Ormon, Alex, Sadokat, Ziroat-70, Iqbol, Shokiri, and Safedaki Ishkoshimi based on phenotypic and genotypic results. Some lines were highly resistant to stripe rust (4 varieties), leaf rust (5) and stem rust (9), but the genes responsible could not be identified. They may possess new resistance genes. We thus identified combinations of major and minor rust resistance genes in Tajik wheat varieties. These varieties can now be used by breeders in Tajikistan as crossing parents to develop new varieties with durable resistance to the rusts.

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Divergent evolution of the Jackie pathotype of Puccinia striiformis f. sp. tritici between Australia and New Zealand

Cuddy New South Wales Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Australia

Based on historical data, Australia and New Zealand (NZ) form a single epidemiological unit for cereal rusts. The dominant westerly wind pattern produces a one-way pathway of pathogen movement from Australia to NZ. Until 2002, pathotype analysis of cereal rust pathogens for NZ was conducted at the University of Sydney, Plant Breeding Institute. Over that time, windborne dispersal of members of the Pst 104 pathotype lineage to New Zealand was confirmed. Historically, pathotypes of Pst introduced to New Zealand have taken different evolutionary pathways to their Australian relatives, including a higher diversity of step-wise mutant isolates, often with different virulence profiles. A preliminary screen of Pst in NZ was conducted in January 2013 and a broader survey was conducted in 2014. Initial results confirmed that the Australian pathotype (pt.) 134 E16 A+ YrJ+ had crossed to NZ. The designation “YrJ+was allocated to indicate virulence for an unidentified, probably rye-derived, resistance gene in the Australian triticale cultivar ‘Jackie’. The divergent evolution of this pathotype in NZ relative to Australia is of interest. In NZ, this pathotype subsequently acquired virulence for Yr10 to produce pt. 150 E16 A+ YrJ+. In Australia, Yr10 virulence had previously evolved in pt. 134 E16 A+, the progenitor of pt. 134 E16 A+ YrJ+. Only two mutational derivative pathotypes have evolved from pt. 134 E16 A+ YrJ+ in Australia. The first acquired virulence for an adult plant resistance gene in another triticale variety, ‘Tobruk’, and the second acquired virulence for Yr27. Despite being present in both Australia and NZ, pt. 134 E16 A+ Yr17+ has dominated the Australian Pst population whereas in NZ the predominant pathotype appears to be 134 E16 A+ YrJ+. Since the rust resistance genotypes of NZ varieties are poorly characterised, no conclusions can yet be reached as to whether this difference in dominant pathotype is due to selection or chance.

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