The University of Sydney
Davinder Singh, Peter Dracatos
Following the introduction of wheat stripe rust into Australia in 1979, an uncharacterized resistance (YrA) was identified in both Australian and International spring wheats. Genetic analyses of YrA indicated it was a pair of complementary genes, which were mapped to chromosomes 3DL and 5BL and designated Yr73 and Yr74, respectively. While selection Avocet 'R' carries both genes, selection Avocet 'S' carries Yr73 only. P. triticina pathotype (pt.) 104-1,2,3,(6),(7),11 +Lr37 ("104-VPM"), first detected in Australia in 2002, most likely arose via mutation from pt. 104-1,2,3,(6),(7),11 ("104"), with added virulence for Lr37. Interestingly, while both pathotypes are avirulent on Lr13, 104-VPM shows a much lower Infection Type (IT, ";1") than pt. 104 ("X++3") on several genotypes carrying Lr13 (e.g.Avocet 'R', Avocet 'S'). Other Lr13 genotypes (e.g. cv. Hereward) respond similarly to both pts ("X++3"). Genetic analyses of 4 doubled haploid (DH) populations based on intercrosses between Avocet 'R' and genotypes lacking Lr13 segregated in a 1:7 ratio to pt. 104-VPM (";1" : all other ITs). Two populations fixed for Lr13 (viz. Hereward/ Avocet 'R' and Estica/Avocet 'R') segregated 1:3 to pt. 104-VPM (";1" : all other ITs). This segregation pattern fitted a model where two complementary genes interact with Lr13 to generate the low (IT ";1") IT. Mapping of a Teal/Avocet 'R' DH population using 92 lines and 9,035 DArT-Seq markers identified three QTLs: chromosome 2BS (Lr13); chromosome 3DL (co-located with Yr73); chromosome 1DS. These results suggest that Yr73 acts in a complementary manner with a gene on chromosome 1DS to confer leaf rust resistance (IT "X"), and that these complementary genes are additive with Lr13. It appears that Yr73 is a modifier of two independent genes in wheat, one conferring resistance to stripe rust (Yr74 on chromosome 5BL), and one conferring resistance to leaf rust (LrAv on chromosome 1DS).
University of the Free State and Seed-Co
Vicky Coetzee, Cornelia M. Bender, Renée Prins, Zacharias A. Pretorius
Notwithstanding the re-emergence and importance of wheat stem rust caused by Puccinia graminis f. sp. tritici (Pgt), the degree of protection provided by different types of resistance has not been carefully investigated in contemporary studies. Seven wheat entries were exposed to stem rust infection and fungicide response in a split-plot field experiment over two seasons. Severe epidemics of Pgt race PTKST, generated by frequent inoculation of spreader rows within and around the trial, developed in both years. By comparing grain yield in rusted and fungicide sprayed plots, varieties SC Nduna (Sr31) and SC Stallion (Sr2+Sr31) sustained mean yield losses of 28.8% and 20.7%, respectively. From entries with adult plant resistance (APR), Kingbird recorded a loss of 10.1% as compared to W1406 (19.5%) and W6979 (15.4%). Grain yield of SC Sky which exhibits all stage resistance (ASR) was reduced by 6.4% over the two seasons. The highest yield loss (47.9%) was measured for Line 37, the susceptible control. A significant linear relationship occurred between percentage yield loss and AUDPC in both seasons (R2=0.99 and 0.83). This study showed that not all sources of APR to stem rust provided the same level of protection under severe disease pressure. In the absence of virulence for SC Sky, ASR conferred the most protection.
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.
Wheat Research Institute, Ayub Agricultural Rsearch Institute Faisalabad
Amna Kanwal, Mehwish Makhdoom, Javed Ahmed, Makhdoom Hussain
Wheat is the most important cereal crop in Pakistan because it contributes major portions of daily calorie intake. Rust is an increasing threat to wheat production and ultimately food security in Asian countries. The purpose of the present study is to identify the suitable wheat lines that could significantly resist rust pathogen without compromising yield. 60 durum wheat lines, entered in preliminary and regular yield trials, were tested for various morphological and physiological traits along with adult plant disease reaction under natural rust infestation. Results indicated that there was higher incidence of yellow rust as compared to leaf rust as ten genotypes were susceptible to leaf rust. Whereas seven lines were moderately susceptible, 14 were moderately resistant and two were completely susceptible to yellow rust. These findings suggested that future breeding program should be directed towards the developments of resistant cultivars that could resist variable strains of rust pathogen under changing climatic conditions.
Ruth Wanyera, Godwin Macharia, Ravi Singh, Ayele Babebo, Girma Bedada
An effective partnership between CIMMYT, KALRO, EIAR and Delivering Genetic Gains in Wheat (DGGW) project on global stem rust phenotyping has made a significant progress and impact on the Global wheat community in addressing the threat of Ug99 race group and other important stem rust races in the region. International stem rust phenotyping networks play a key role in evaluating global wheat germplasm from many countries and institutions: identifying new sources of resistance, pre-breeding, CIMMYT-Kenya shuttle breeding, pathogen survey and surveillance, varietal release and genomic selection. About 600,000 lines have been screened against Pgt race Ug99 and derivatives since 2005, and the screening capacity at KALRO has increased to 50,000 lines each year from over 20-25 countries and research institutions each year. The results from international nurseries show a shift to higher frequencies of lines with resistance to race Ug99 since the screening activities were initiated in 2008.
KALRO and EIAR and several national programs have a dynamic and successful breeding programs that benefit from collaboration, testing, and release of materials coming out of the CIMMYT breeding program. The release of over 15 varieties in Kenya as well as in Ethiopia and more than 90 varieties released in several countries globally over the years is a testament to the success of the program. with spillover effects of varieties released in Burundi, Rwanda, and Uganda.
CIMMYT-Kenya shuttle breeding has resulted in rapid recycling of over 2000 breeding populations each year between Mexico and Kenya to evaluate and select lines in early generations against virulent stem rust races in Kenya to ensure lines have adequate levels of resistance are advanced not only in early generations of breeding cycle but also materials in the yield trails (10,000 annually) that are later constituted as international nurseries and distributed to National programs and partners.
University Mentouri of Constantine, Algeria
Wheat is the world's most widely grown food crop. New races of pathogens frequently overcome current resistant varieties. To address this issue Algeria has strategies for immediate action, medium term protection and long-term research efforts to develop new resistant wheat varieties. Yellow rust is a very important disease of wheat in Algeria where 60% of the wheat crop is grown under cooler high elevation climate conditions (2?C ? 15?C). Crop losses reached 80% during the 2004/2005 epidemics. Strategies adopted to reduce the risk of wheat rust are ongoing yearly surveillance, awareness, and early warning systems to farmers; and breeding and developing new varieties with high yield potential and durable resistance. Several highly resistant varieties (Tiddis, Boumerzoug, Massine, Akhamokh and Yacine) were selected and promoted following seed multiplication and commercial release. They are also widely used in crosses to improve local varieties. The newly released varieties are being distributed to farmers that grow susceptible varieties. This gene deployment will provide a natural barrier between eastern to western Algeria to intercept the major direction of air flow. Fungicide control is now routinely applied soon after rust detection or even preemptively. The level of awareness for wheat rusts across Algeria is now very high. Training among farmers for visual detection is widely promoted by plant protection and extension services. These strategies have been very effective in mitigating the threat of wheat stripe rust such that losses have not exceeded 10% over the last five years.
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..
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.
Kazakh National Agrarian University
Yerlan Dutbayev, Alexei Morgounov
Kazakhstan is among the ten largest grain exporters in the world. Winter wheat in Kazakhstan is mainly cultivated in the southern and south-eastern regions on an area of 1.5-2 million hectares, including 140-170 thousand hectares - in irrigated lands. Annual losses of wheat yield from diseases can reach up to 30-40% or more. For Kazakhstan, the most dangerous diseases of winter wheat are stripe rust and leaf rust. Work is under way in Kazakhstan to find new donors for resistance to leaf rust and stripe rust and the use of these donors in breeding. The aim of this research was to expand genetic diversity through crosses and development of lines obtained by the method of remote hybridization, as well as selection of new sources of resistance of bread wheat to leaf rust and stripe rust in southeast Kazakhstan. The subject of the research were 49 hexaploidsynthtic lines of Kyoto University (Japan) and CIMMYT and commercial varieties of winter wheat in the Almaty region. We screened synthetic hexaploid wheat for resistance to diseases. A collection of hexaploid synthetic wheat lines resistant to the diseases and adapted to various conditions of the Almaty region has been established. The character of inheritance of resistance to diseases in crosses of synthetic wheat with local cultivars based on comparison of the first generation and parents was studied. Evaluation of phenotypes inheritance of resistance in hybrids in the generation of F2, showed that 9crosses of synthetic wheat(LANGDON/IG 48042//ZHETISU, LANGDON/IG 48042//FARABI, LANGDON/KU-20-8//AJARLY, LANGDON/KU-2075//AJARLY, LANGDON/KU-2097// ZHETISU, LANGDON/KU-2075//FARABI, LANGDON/KU-2100//STEKLOV, LANGDON/KU-2144//NAZ, LANGDON/KU-2076//NAZ)possess the dominant resistance genes to leaf rust.Seven lines(LANGDON/ KU-2075/AJARLY, LANGDON/KU-2075/FARABI, LANGDON/KU-2092/FARABI, LANGDON/KU-2100/NAZ, LANGDON/KU-2097/STEKLOVINDAYA, LANGDON/KU-2097/ZHETISU, LANGDON/KU-2097/ AJARLY) possess from one to several dominant resistance genes to stripe rust.
University of Minnesota, St. Paul, MN 55108, U.S.A
Ruth Dill-Macky, Ruth Wanyera, Sridhar Bhavani, Worku Bulbula, Matthew Rouse
Stem rust caused by Puccinia graminis f.sp. tritici (Pgt) is one of the major constraints to wheat (Triticum aestivum) production worldwide. Pgt races have rapidly evolved in several geographical regions due to the deployment of single resistance genes resulting in boom and bust cycles, hence combinations of resistance genes through pyramiding ensures durability of resistance in wheat varieties. Spring wheat line CI14275 displayed high levels of field resistance to stem rust in Kenya and USA compared to the parents in its pedigree (Thatcher, Kenya Farmer & Lee). To understand the genetics of resistance in CI14275, 114 Recombinant Inbred lines (RILs) were developed from the cross CI14275/LMPG-6 and screened for seedling response to Pgt races TTTTF, TPMKC, TRTTF, TTKSK & RTQQC. Chi-square goodness of fit tests suggested one-gene, three-genes, and four-genes segregated for response to races TTTTF, TPMKC and RTQQC, respectively. The RILs were all susceptible to races TTKSK and TRTTF. CI14275 showed intermediate low infection types only against races TPMKC (23-) and TTTTF (1+3C). Field screening of the population was completed in Kenya, Ethiopia and St. Paul where CI14275 showed high levels of resistance TMR (Kenya), 5MS (Ethiopia) and 5RMR (St. Paul) against the prevalent races in the stem rust screening platforms. LMPG-6 displayed susceptible responses ranging from 70S-90S in the three locations. 90K wheat Single Nucleotide Polymorphism (SNP) marker platform will be used to genotype parents and the population.