National Institute of Agricultural Research
Nsarellah Nasserlhaq, Wuletaw Tadesse, Ahmed Birouk
In the context of climate change, drought is one of the most important and complex abiotic stresses affecting crop production worldwide. The adoption of an appropriate technological package, principally drought tolerant varieties, may overcome these challenges to meet global food security needs for the rapidly growing human population, particularly in developing countries. Therefore, this research was carried out to identify efficient phenotypic and genetic selection criteria to identify drought tolerant wheat varieties. In this perspective, 200 diverse elite bread wheat lines from ICARDA and CIMMYT were evaluated under four Moroccan environments during the 2015 and 2016 seasons for yield and 15 agro-physiological traits. The same set of genotypes was genotyped using 15k SNPs. Significant environment and genotype environment interaction effects were observed for yield. Average yield reached 3.18t/ha and ranged from 2.45 to 4.27t/ha. The secondary traits were mostly dominated by the environment effect (p<0.001). Based on correlation and regression analysis between grain yield and phenotypic data, the biomass, grain number per m<sup>2</sup> and to a lesser extent fertile spikes number and thousand kernel weights (depending of drought scenarios) can be more reliable traits than yield for the identification of drought tolerant genotypes. Moreover, the ground cover and canopy temperature depression can be used as supplementary criteria for more accurate selection. Slow selection on the basis of phenotypic traits may be accelerated and improved by using molecular markers. The genetic analysis highlighted significant SNPs and identified new QTLs linked to yield and the most efficient phenotypic traits under drought conditions. These findings could be useful for breeding drought-resistant wheat cultivars using marker-assisted selection to accumulate these favorable alleles of SNPs associated with yield-related traits to increase grain yield.
QAAFI, The University of Queensland
Robert McIntosh, Peng Zhang, Sami Hoxha, Adnan Riaz, Burkhard Steuernagel, Brande Wulff, Evans Lagudah, Lee Hickey, Sambasivam Periyannan
Wheat is one of the most important staple food and agricultural crop cultivated worldwide. To meet the demands of the raising human population, global wheat production has to be increased which is however declined due to appearance of highly virulent strains of Puccinia striiformis f. sp. tritici (Pst) fungus causing stripe rust disease. Globally, the incidence of stripe rust is effectively managed through the deployment of host plant mediated genetic resistance. But as the resistance present in the current wheat cultivars are ineffective, new sources of resistance particularly from pathogen unexposed genetic resources are of urgent need to prevent stripe rust epidemics. Landrace collections with rich genetic diversity and being less exposed to prevalent pathogen are of valuable source for resistance to new pathogens. In this study, a total of 295 landrace accessions collected by the famous Russian botanist Vavilov was screened for stripe rust resistance using the two predominant lineage Pst strains of Australia. Six accessions with good resistance against the two aggressive Pst strains were selected for genetic characterization and for utilization in global wheat breeding. Characterisation of these novel resistance were undertaken using combination of conventional and advanced genetic tools. While the conventional approach involves the traditional map based gene cloning, the other tool is the recently identified rapid method based on mutagenesis, targeted gene capture and next generation sequencing called "MutRenSeq". Subsequently, the identified novel resistant traits were transferred into elite wheat cultivars through the combination of linked molecular markers and speed breeding techniques. Thus along with the identification of novel resistance, elite wheat cultivars with broad spectrum stripe rust resistance were also generated through the use state of art techniques to sustain global wheat production from the rapidly evolving stripe pathogens.
International Center for Agriculture Research in Dry Areas (ICARDA)
ahmad amri, El-Haddoury Jamal
Constant climatic change and rapid evolution of diseases and pests have created challenges for plant breeders to find novel sources of resistance within cultivated gene pool. However wild (alien) relatives of crops still carries many promising resistance genes to biotic and abiotic stresses. Plant breeders around the world have successfully attempted to recover some of the beneficial genetic diversity lost (or never included) during the domestication and crop improvement process by crossing cultivated varieties with wild species to introgressed many valuable genes into crops like wheat and barley. This pre-breeding attempt to regain the genetic diversity of crops based on crop wild relatives (CWR) had been started at ICARDA 1994. Furthermore, The Global Crop Diversity Trust (GCDT) recently provided a grant to ICARDA within the Crop Wild Relatives (CWR) project to strengthen the research on use of genetic resources in pre-breeding of barley and grass pea. The pre-breeding activity in barley is focused on transferring genes of resistance to complex diseases and pests (scald, spot blotch and barley gall midge), improving tolerance to drought, heat and salinity, and enhancing the nutritional value through improving Iron and Zinc concentrations and amylases activity. Crosses were made between wild barely H. Vulgare X cultivated barley H. Vulgare subsp. H. spontaneum. The main objective of pre-breeding in Grasspea is transferring genes of low or no ?-ODAP from crossable species L. cicera and L. amphicarpus, L. tingitanus, L. aphaca, L. odoratus, L. sphaericus, L. nissolia, and L. aureus. Interspecific crosses were made between L. sativus x L.cicera followed by embryo rescue. Currently all the pre-breeding lines with targeted traits are under screening against the respective selection pressures using precision phenotyping..
USDA-ARS Cereal Disease Laboratory
Maria Ordonez, Silvia German, Kun Xiao, Amy Fox, Maricelis Acevedo
The leaf rust pathogen, Puccinia triticina is widespread across all major wheat growing regions worldwide. Collections of P. triticina were obtained from common and durum wheat in North America, South America, Europe, South Africa, the Middle East, East Africa, Russia, Central Asia, China, Pakistan and New Zealand in order to determine the genetic diversity within each region and genetic relationship between regions. A total of 831 single uredinial isolates were characterized for virulence to isogenic lines of Thatcher wheat and for molecular genotype at 23 SSR loci. The isolates in East Africa and Europe were the most diverse for the average number of effective alleles per locus, while the populations in Russia and North America were the least diverse. The isolates in Europe and South America had the highest number of multilocus genotypes of 81 and 75, respectively, and were the most diverse for Shannon's genotypic diversity. All populations had significantly higher levels of Ho compared to He at individual SSR loci, and had highly significant values of Ia and rd which indicated clonal reproduction. Europe had the highest number of distinct SSR genotype groups with eight, and Russia had only two SSR groups. The populations in North America and South America; Russia and Central Asia; the Middle East and East Africa; were closely related for SSR genotype based on Nei's genetic distance. Based on k means clustering and DAPC of SSR genotypes, isolates virulent to durum wheat were placed into a single separate group, and isolates virulent to common wheat were placed into five other groups. Twenty-seven SSR genotypes were found in different continental regions. Isolates with identical or highly related SSR genotypes also had identical or similar virulence, which indicated historical and current migration of P. triticina worldwide.
Jamal El Haddoury, Ahmed Amri
Malika', a hard red spring wheat (Triticum aestivum L.) cultivar developed using doubled haploid technology by the Institut National de la Recherche Agronomique (INRA), Morocco, and tested as 06DHBW48, was approved for release in 2016 by the Office National de S?curit? Sanitaire des Produits Alimentaires (ONSSA), Morocco. Malika was selected from the doubled haploids derived from the cross 'Achtar3*//'Kanz'/Ks85-8-4). Achtar and Kanz are Moroccan varieties originating from segregating populations from CIMMYT. Achtar and Kanz are a well adapted to Moroccan conditions but susceptible to the Hessian fly, yellow rusts and some races of leaf rust. 'Achtar' was crossed with it in order to incorporate the Hessian fly resistance, yellow rust resistance and leaf rust resistance and 'Achtar' was crossed with Kanz/Ks85-8-4 having resistance to Hessian fly, yellow rust and leaf rust. Backcrossed 3 times with 'Achtar', and selected lines having resistance to the Hessian fly, yellow rust and leaf rust from the population derived from each backcross. Finally the selected the resistant line was used develop doubled haploids. The doubled haploid lines produced were tested in the laboratory and field for Hessian fly and the rust resistance. The resistant lines were incorporated in the multi-local yield trials and three promising lines with the resistance to Hessian fly, yellow rust and leaf rust and better yield and quality were submitted for registration in the official catalog in 2014. After 2 years of testing (years 2014-15 and 2015-16), one line (06DHBW48) was accepted for the registration and designated as 'Malika'. 'Malika' is a semi-dwarf variety, well adapted to semi-arid regions, early maturing, high yielding, tolerant to drought and resistant to Hessian fly, leaf rust and yellow rust.
Genetic Resources Institute, Azerbaijan
N. Aminov, A. Jahangirov, H. Hamidov, Aigul Abugalieva, Vladmir Shamanin, Alexey Morgunov
Hexaploid synthetics have become widely used in bread wheat improvement in recent years, enabling the introduction of specific traits as well as enhancing genetic diversity and development of valuable germplasm. This study demonstrated the difference between two groups of primary synthetics in terms of development rate, plant height, rust reactions, and productivity components. During 2015 and 2016, three groups of synthetics were studied in Azerbaijan (3 sites): Baku (0 masl) under irrigated conditions, Gobustan (850 masl) under dry rainfed conditions and Ujar (20 masl) under irrigated conditions with high salinity. Germplasm was also evaluated for diseases and agronomic traits in Omsk (Russia) in 2016.
All primary synthetics were resistant to leaf rust, several to stem rust, and few to stripe rust. Stripe rust occurred in all years at all sites, proving its importance as major wheat pathogen. Its severity reached intermediate levels in Baku in 2016 (33.7%) and in Gobustan in 2015 (26.8%), and epidemic level in Gobustan in 2016 (72.7%). Gobustan also experienced high levels of stem rust in 2016. These two diseases substantially reduced grain productivity in Gobustan in 2016, especially 1000 kernel weight (30.2 g) and grain weight per spike (1.17 g). . Superior genotypes from all three groups were identified that combine high expression of spike productivity traits and stress tolerance index. Five superior synthetics were selected from each of the three groups, based on grain weight per spike. Only four of these demonstrated resistance to stripe rust (entries 13, 15, 31, and 32). Japanese synthetics (group 3) were susceptible to stripe rust but all demonstrated resistance to stem rust. Synthetics from groups 1 and 3 were all resistant to leaf rust when tested under severe disease pressure in Omsk in 2016.
Wheat Research Institute, AARI, Faisalabad, Pakistan
Ghulam Mahboob Subhani, Makhdoom Hussain, Mehvish Makhdoom
Rust is the single largest factor limiting wheat production in Pakistan. According to the FAO reports, countries in the predicted immediate pathway of Ug99 grow more than 65 million hectares of wheat, accounting for about 25% of global wheat harvest.
Rice, a member of the same family (Poaceae) is not attacked by any rusts. Wheat, an allo-hexaploid is responsive for wide crossing. It has previously been successfully crossed with its several wild relatives and different other crop species like corn, pearl millet etc. Based on the above facts wheat ? wild rice crossing has been attempted to incorporate rust resistance from rice to wheat. Successful crosses were made under in-vitro conditions. Surviving plantlets developed from these crosses were assayed for any genetic material introgressed from rice. Different cytological / molecular techniques were used to detect the introgression (Squash preparations from root tips, FISH, GISH, SSR etc.). Two hundred and fifty primers specific to rice chromatin were used to look for the introgression of rice chromatin into hybrids. Seven primers amplified the fragments in hybrids indicating the possible introgression of rice chromatin in wheat x rice hybrids but in-situ hybridization didn't confirm that introgression. So further testing of these hybrids is needed.
ICAR-IIWBR, Regional Station, Flowerdale,Shimla 171002 H.P. India
Pramod Prasad, OmPrakash Gangwar, Hanif Khan, Siddanna Savadi, Subodh Kumar
Stem rust (Puccinia graminis tritici) (Pgt) epidemics have been reported from many wheat growing areas of the world. Stem rust races with virulence to Sr31 (Ug99 type races),are a threat to wheat producing African countries. Currently 11 different variants of the Ug99 lineage have been reported from different countries. Despite no report of Ug99 variants from any of the South Asian countries, the efforts are in place to counter the possible introduction of virulent wheat stem rust races. Stem rust surveillance has been a major component of the rust resistance breeding worldwide. This study reports virulence phenotypes and functional SSR marker based genotypes among stem rust collections in the Indian subcontinent during 2009 to 2015.
Wheat stem rust samples were analyzed on differential sets used for pathotype identification in India. Twelve pathotypes of Pgt were identified in a total of 574 samples analyzed. Pgt pathotypes 40A and 11 were identified in 36% and 32% of the samples, respectively. The stem rust resistance genes Sr7a, Sr26, Sr27, Sr31, Sr32, Sr33, Sr39, Sr40, Sr43, SrTmp and SrTt3 were found to confer resistance to the field population identified during this period. The analysis of SSR marker genotypes data revealed a high degree of variability in the Pgt population, with mean gene diversity and polymorphic information content (PIC) values of 0.56 and 0.50, respectively. STRUCTURE software divided the Pgt populations in to four subpopulations with some admixtures. The FST values of pairs of subpopulations ranged from 0.35 to 0.93 which indicated that the four sub-populations were significantly differentiated. The analysis of molecular variance (AMOVA) determined that 16%, 69% and 15% of the totl variation was between population, among and within individuals, respectively. The information generated here could be a useful guide for resistance breeding and gene deployment programmes for saving South Asian wheat from stem rust.
INIA Uruguay and Dep. Plant Pathology, Kansas State University, US
Pierina Clerici, Richard Garcia, Fernando Pereira, Noelia Perez, Martin Quincke, Silvia German
Leaf rust (LR) and stem rust (SR) are threats to global wheat production and new races frequently overcome resistance genes deployed in wheat cultivars. Identification of new sources of resistance is a major goal for many pre-breeding programs. The objective of this study was to investigate the genetic basis of resistance to LR and SR in a diverse South American wheat panel. Molecular markers for known resistance genes and GBS were used to dissect genetic components. The wheat panel of 122 lines was characterized under field conditions at La Estanzuela Research Station, Uruguay, for disease severity (DS) to LR (2014 and 2015) and SR (2015), and LTN (leaf tip necrosis). Final DS for LR ranged between 0 and 95%, with mean values of 40% (2014) and 46% (2015). For SR, final DS ranged between 0 and 50%, with a mean value of 5%. The frequencies of positive diagnostic resistance markers among accessions were 20.5% for Lr34/Sr57, 6.6% for Lr68, 3.3% for Sr2/Lr27, 23% for Sr31/Lr26, 20.5% for Sr24/Lr24, 9.4% for Sr25/Lr19, and 0% for Sr39/Lr35. Of all the LR/SR resistance genes, only the effect of Lr68 was significant when predicting LR DS. Seventeen lines were identified with combinations of two genes, but no combination conferred a significantly improved level of resistance. Preliminary GWAS analysis for LR response on a subset of 86 lines revealed several QTLs, with a major QTL explained by Lr68. Lines with good levels of resistance to LR and SR, high expression of LTN, and absence of markers for the studied resistance genes were identified, indicating that there are other genes involved in resistance. Future research involving the testing of additional molecular markers for other known resistance genes, and a deeper GWAS analysis, will provide further information about the resistance genes present in this wheat panel.
Global Rust Reference Center (GRRC), Aarhus University, Denmark
Mogens Støvring Hovmøller, Jens Grønbech Hansen, Annemarie Fejer Justesen, Tine Thach, Julian Rodriguez-Algab, Dave Hodson, Biagio Randazzo
In 2016, severe epidemics of yellow (stripe) rust were observed on durum and bread wheat in European regions where the diseases in the past were insignificant or absent. Stem rust was also observed at epidemic levels for the first time in more than 50 years in Europe. On Sicily, both yellow and stem rust caused epidemics on cultivated durum and bread wheat and numerous breeding lines. In 2017, surveys in farmer fields and trial monitoring were carried out in Southern Italy during April-June. A total of 61 farmer fields and 9 experimental plots were inspected and rust samples collected. Despite unfavourable weather conditions for rust development, stem rust, yellow rust and leaf rust were detected on 86%, 50% and 14% of the surveyed sites, respectively. The surveys on Sicily covered approximately 70% of the durum wheat area, and data uploaded and visualised on the Wheat Rust Toolbox. On mainland Italy and Sardinia, yellow rust was observed, and sampled from nine fields in Sardinia and two in Puglia, whereas stem rust was detected and sampled in experimental plots in Sicily, Sardinia, Puglia, Lazio and Emilia Romagna. A total of 94 samples of stem rust, 30 samples of yellow rust, and 3 rust samples from Berberis aetnensis were sent to GRRC. Preliminary results of yellow rust genotyping and race phenotyping showed prevalence of race Triticale2015. Warrior(-) and a new race (Pst'New'- First detected in 2016) were also detected. For stem rust, TTTTF and TTRTF were detected in Sicily and mainland Italy and TKTTF was identified in Sardinia. Susceptibility of major commercial durum cultivars and breeding lines suggests the need for both durable resistance breeding and systematic surveys coupled to an early warning system.