Ethiopian Institute of Agricultural Research (EIAR)
Stripe rust caused by Puccinia striiformis f.sp.tritici, is one of the major diseases of wheat in the world. Experiments were carried out at two sites in Ethiopia (Kulumsa and Meraro) during the 2015 cropping season to evaluate the response of 198 elite bread wheat genotypes and two checks to the prevailing races of stripe rust at adult plant and seedling stage. The genetic profile of these genotypes was assessed using 13006 SNP markers and an association mapping was explored to determine marker?trait association. About 72.5% and 42.5% of the lines exhibited resistance at Kulumsa and Meraro, respectively. Out of 198 genotypes tested in the greenhouse, 31% exhibited common resistance for Kubsa and mixed stripe rust isolate. Only 8966 of the SNPs were polymorphic, only these were used for association mapping analysis. These markers spanned an average density of 3.47 cM per marker, with the poorest density on the D genome. Almost half of these markers were on known chromosomes, but had no position on the consensus map of bread wheat. Analysis of population structure revealed the existence of three clusters and the estimated genomic wide Linkage Disequilibrium (LD) decay in this study ranged from 0 to 50 cM. 53 SNPs in ten genomic regions located on wheat chromosome 1AL, 2AL, 2BL, 2DL, 3BL, 4BL, 4DL, 5AS, 7AL and 7BL were identified. Thirty nine SNP markers in five genomic regions at Kulumsa and 14 SNP markers in six genomic regions at Meraro explained more than 25.5% and 35.1% of phenotypic variability respectively. For seedling stage, 21 markers in ten genomic regions located on wheat chromosomes 1B, 2A, 2B, 3A, 3B, 4B, 4D, 5A, 6B and 7B were associated with resistant. These loci may be useful for choosing parents and incorporating new resistance genes into locally adapted cultivars.
CREA-Research Centre for Cereal and Industrial Crops
Elisabetta Mazzucotelli, Oadi Matny, Antonietta Saccomanno, Raffaella Battaglia, Francesca Desiderio, Agata Gadaleta, Nicola Pecchioni, Pasquale De Vita, Giovanni Laido, Luigi Cattivelli, Brian Steffenson
The recent emergence of new widely virulent and aggressive strains of rusts (particularly stripe and stem rust) is threatening Italian durum wheat (Triticum turgidum L. var. durum) production, especially under the trend of higher temperature and humidity. A big effort has been undertaken to explore the genetic variability for resistance to these fungal pathogens and discovering novel resistance genes. In particular, a wide set of tetraploid wheat lines was genotyped with several thousands of SNP markers and used for association mapping. This large collection consisted of a group of durum wheat cultivars, produced from the beginning of the last century up to now, a collection of wild emmer wheats (T. dicoccoides), and lines belonging to other wild and domesticated tetraploid subspecies, as a large untapped source of genetic diversity. In a tight cooperation with the University of Minnesota, this collection was evaluated for reaction to several races of stem and stripe rust pathogens in both controlled greenhouse and field conditions. Among the genotypes belonging to the collection are parents of segregating populations which were used for the validation of mapping results. Novel resistance loci were identified, that can be incorporated into new durum varieties through breeding programs. The QTLs found in this study, together with those available in literature, were projected to the recently sequenced durum wheat genome in order to define more precisely the chromosome regions and candidate genes involved in resistance to rusts. Lines which were resistant to multiple races of rust pathogens were also found among both T. dicoccoides and durum wheat cultivars as a source of resistance genes, whose cloning will be undertaken based on the results here obtained.
This study was supported by the Italian Ministry of Foreign Affairs and International Cooperation, with the special grant RES-WHEAT.
All-Russian Institute of Plant Genetic Resources
Wheat varieties with single effective gene for leaf rust resistance often quickly become susceptible because of multiplication of virulent Puccinia triticina genotypes. One of the methods to elongate term of effectiveness is to combine two genes in host genotype. To note, it is impossible to distinguish phenotypically plants or families having one or two genes in hybrid populations; the only method is to use PCR producing DNA markers linked to each gene for resistance. It is not convenient when necessary to analyze thousands plants or especially families of crosses between carriers of certain genes. At inoculation of wheat seedlings having Lr 9, 19, 24, 47, 29 and Sp with rust population from North-West region of Russian Federation all of them were absolutely resistant, so these genes may be considered to be effective in this region. Rust population was multiplied on cv. Leningradka leaf segments placed on cotton wool wetted with solution of maleic acid hidrazide (10 mg/l) + potassium chloride (0.48 g/l) +monosubstituted sodium phosphate (0.66 g/l) and used to infect seedling of the lines constantly poured with the solution. Rare pustules were recorded on each line. Isolates from the line were combined, multiplied and used to infect the lines set. Interaction specificity was shown for carriers of certain genes for resistance and inoculums. We propose to infect seedlings of hybrid wheat populations with mixtures of isolates virulent to first gene and those virulent to second one at use of above-mentioned method to multiply rust and grow plants. Seedlings resistant to that inoculum have both genes for resistance. If we have F3 or later families it is possible to use original population without selection of virulent isolates; in this case the method allowed removing progenies of heterozygous plants. With this approach we developed lines possessing combinations of Lr9+Lr24 and Lr9+Lr47 genes
Research centre SELTON
Alena Hanzalova, Jaroslav Matyk, Pavel Bartos
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.
Ethiopian Institute of Agricultural Research
Information about changes associated with advances in crop breeding is essential for understanding yield-limiting factors and developing new strategies for future breeding programmes. Thirty-six durum wheat varieties released since 1966 were evaluated in three replications of the Randomized Complete Design at Debre Zeit and Akaki, Ethiopia during the 2016 cropping season to estimate the amount of genetic gain made over time in grain yield potential, yield-associated traits and in protein content. Analysis of variance revealed significant differences among varieties for all 16 quantitative traits, protein content and protein harvest in Kg ha-1 at each of the locations. Grain yield varied between 1.66t ha-1 for Arendato released in 1966 to 3.90t ha-1 for Megenagna released in 2012 with mean of 2.952t ha-1 at Debre Zeit. At Akaki yield range was between 2.45 and 5.04t ha-1 with mean of 3.992t ha-1. 25 varieties surpassed Arendato (3.754t ha-1) at this location. In the combined ANOVA significant difference between the varieties was observed only for spike length, spikelets spike-1, grains spikelet, grains spike-1, plant height, days to flowering, thousand grain weight and hectoliter weight. Varieties specifically adapted to only one of the locations, widely adapted varieties and varieties not adapted to any of the locations were identified. Regression analysis revealed that grain yield has increased by 22kg ha-1 year-1 since 1966; an increase of 40.6% over yield in 1966. This was accompanied with a significant decline of 11.4% in spike length, 6.7% in spikelets spike-1, 17.9% in protein content and 31.2% in protein yield ha-1 and a significant increase of 41.1% in grains spikelet-1, 32.9% in number of grains spike-1, 22.3% in thousand grain weight, 17.8% in grain filling period, 23.9% in seed growth rate, 40.1% in grain yield production rate, 7.9% in harvest index.
Seed and Plant Improvement Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran.
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Stripe rust of wheat, caused by Puccinia striiformis f. sp. trirtici (Pst) is an important disease in many parts of Iran. Over last two decades several epidemics have occurred in Iran causing the breakdown of widely utilized sources of resistance in wheat cultivars. Fifty isolates were collected from different parts of Iran during 2017. Eight isolates of Pst. from 2017 have been processed to date for race analysis. Infection types were assessed on a 0-9 scale 16 and 18 days after inoculation using a scale similar to that described by McNeal et al. (1971). Infection types (ITs) 7 to 9 were regarded as virulent (susceptible) and lower than 7 were avirulent. Pathotypes 102E158A+,Yr27; 6E158A+,Yr27; 102E158A+,Yr27; 166E154A+,Yr27; 38E174A+; 38E158A+,Yr27; 238E190A+,Yr27 and 38E190A+,Yr27 were identified. Pathotype 238E190A+,Yr27+ (from West of Iran) was more aggressive during this study. Plants with Yr1, Yr4, Yr5, Yr10, Yr15, Yr24 and YrSP were resistant to all pathotypes. Pathotypes with virulence on plant with gene/s Yr2, Yr6, Yr7, Yr8, Yr9, Yr25, Yr26, Yr27, Yr32, YrSD, YrSU, YrND and YrA were more common. Seedling tests of Iranian wheat cultivars to race 238E190A+,Yr27+ showed that the new released cultivars that included Parsi, Baharan, Bahar, Pishgam, Zareh, Urom, Maihan, Dena, Haydarei and Shabrang were resistant to the new aggressive race with virulence on plants with Yr27.
The University of Queensland, Queensland Alliance for Agriculture and Food Innovation (QAAFI)
Naveenkumar,Athiyannan, Sambasivam, Periyannan, Olga, Afanasenko, Olga, Mitrofanova, Gregory, Platz, Elizabeth, Aitken, Rod, Snowdon, Evans, Lagudah, Lee, Hickey, Kai, Voss-Fels, , , , , , , , , ,
Leaf rust (LR) is an important wheat disease and deployment of resistant cultivars is the most viable strategy to minimise yield losses. We evaluated a diversity panel of 295 bread wheat accessions from the N. I. Vavilov Institute of Plant Genetic Resources (VIR), St Petersburg, Russia for LR response and performed genome-wide association studies (GWAS) using 10,748 polymorphic DArT-seq markers. The diversity panel was evaluated at the seedling and adult plant growth stages using three prevalent Australian P. triticina pathotypes. GWAS applied to 11 phenotypic data sets identified a total of 52 significant marker-trait associations representing 31 quantitative trait loci (QTL). Among them, 29 QTL were associated with adult plant resistance (APR). Of the 31 QTL, 13 were considered potentially new loci, whereas 4 co-located with previously catalogued Lr genes and 14 aligned to regions reported in other GWAS and genomic prediction studies. One seedling LR resistance QTL located on chromosome 3A showed pronounced levels of linkage disequilibrium among markers (r2 = 0.7), indicative of a high allelic fixation. Subsequent haplotype analysis for this region found 7 haplotype variants, of which 2 were strongly associated with LR resistance at the seedling stage. Similarly, analysis of an APR QTL on chromosome 7B revealed 22 variants, of which 4 were associated with resistance at the adult-plant stage. Most of the lines in the diversity panel carried 10 or more combined resistance-associated marker alleles, highlighting the potential of allele stacking for long-lasting resistance.
Cereal Crops Research Institute (CCRI), Pirsabak Nowshera Khyber Pakhtunkhwa-Pakistan
Gulzar,Ahmad, Imtiaz, Muhammad, Khilwat, Afridi, , , , , , , , , , , , , , , , , , , , , , , ,
In the current scenario of climatic change, exploration and development of new stable genotypes performing better under stressed and non stressed environmental conditions is the priority of wheat breeders for exploiting genetic variability to improve stress tolerant cultivars. Late planting is one of the major abiotic stresses, seriously influencing wheat production. In the current study, twenty eight bread wheat genotypes were evaluated independently under normal (optimal) and late (stress) planting conditions at Cereal Crops Research Institute (CCRI), Pirsabak Nowshera Khyber Pakhtunkhwa Pakistan during 2013-14. Analysis of variance revealed highly significant (P < 0.01) differences among the genotypes, planting (sowing dates), and genotype ? sowing dates interactions effects for the studied traits. Generally, reduction in plant height (0.41 to 10.91%) and grain yield (0.36 to 53.35%) was observed among the tested genotypes under late planting as compared to normal (optimal) planting. Least % reduction in grain yield was recorded for genotypes BWL-23 (0.36%), BWL-4(0.76%), BWL-16(1.22%) and BWL-13 (1.78%) and were found tolerant to late planting stress as compared to check (Pirsabak-2008). Eight stress selection indices i.e. Mean productivity (MP), Tolerance (TOL), Geometric Mean Productivity (GMP), Harmonic mean (HM), Stress selection Indices(SSI), Stress Tolerance Index (STI), Yield Index (YI) and Yield Stability Index (YSI) were determined based on mean performance of genotypes evaluated under normal and late planting conditions. Analysis of correlation revealed that plant height and grain yield under normal and late planting conditions, had significant positive correlation with stress selection indices i.e. GM, HM, SSI and YI. These selection indices could be effective in identification of lines/ genotypes to late planting stress tolerant conditions. Based on MP, GMP, HM, STI and YI genotypes i.e. Pirsabak-2008, BWL-23 and BWL-27 were found late planting stress tolerant and could be recommended for sowing in both normal and late planting.
The University of Georgia (UGA)
Suraj Sapkota, James Buck, Jerry Johnson, John Youmans
Leaf rust disease, caused by the fungal pathogen Puccinia triticina, is a major biotic constraint of wheat production worldwide. Genetic resistance is the most effective, economic, and environmentally safe method to control and reduce losses caused by this disease. More than 70 leaf rust resistance genes have been identified and mapped to specific chromosomes; however, continuous evolution of new leaf rust races requires constant search for new sources of resistance with novel QTL/genes. The objectives of this study were to identify sources of resistance, and to map genomic loci associated with leaf rust resistance using genome wide association study (GWAS) approach. Phenotypic evaluation of 297 spring wheat genotypes against a prevalent race of leaf rust in Georgia revealed that most of the genotypes were susceptible, and only 24 genotypes were found resistant. Furthermore, GWAS detected 10 markers on chromosomes 2A, 2B, 6A, 7A, and 7B significantly associated with leaf rust resistance. A marker on chromosome 7AS was identified revealing a novel genomic region associated with leaf rust resistance. The new identified sources of resistance and QTL could be used in wheat breeding programs to improve leaf rust resistance.
Department of Plant Sciences, University of the Free State, South Africa
Marcel Meyer, Robert Park, Christopher Gilligan, Laura Burgin, Matthew Hort, David Hodson, Zacharias Pretorius
Despite being 10,000 km apart, the current study emphasizes the potential vulnerability of Australia to wind-borne Puccinia graminis f. sp. tritici (Pgt) spore introductions from southern Africa. Of four Pgt introductions into Australia since 1925, at least two (races 326-1,2,3,5,6 and 194-1,2,3,5,6) are thought to have originated from southern Africa. Microsatellite analysis of 29 Australian and South African Pgt races confirmed close genetic relationships between the majority of races in these two geographically separated populations, thus supporting previously reported phenotypic similarities. Using Lagrangian Particle Dispersion Model simulations with finely-resolved global meteorological data over a 14-year period and a three-day urediniospore survival time, the study showed that long distance dispersal of Pgt from southern Africa to Australia is possible, albeit rare. Transmission events occurred most frequently from central South Africa, but were also possible from southern South Africa and Zimbabwe; while none occurred from a representative source-location in Tanzania. Direct dispersal incursions into both the western and eastern Australian wheat belts were feasible. Together, the genetic and simulation data strongly support the hypothesis that earlier introductions of Pgt into Australia occurred through long-distance wind-dispersal across the Indian Ocean. The study thus acts as a warning of possible future Pgt dispersal events to Australia which could include members of the Ug99 race group. This emphasizes the continued need for Pgt surveillance on both continents.