Seed and Plant Improvement Institute, Agricultural Research Education and Extension Organization (AREEO), Karaj, Iran
The basidiomycetous fungus, Puccinia graminis f. sp. tritici (Pgt) causes stem rust disease as one of the most destructive wheat pathogens, worldwide. TTKSK and other Pgt races under Ug99 race group are considered as major threats to wheat production in east Africa and CWANA region by defeating the stem rust resistance gene Sr31, while its ineffectiveness was reported in Iran in 2007. Race TKTTF of Pgt caused a severe stem rust epidemic in southern Ethiopia in 2013, and was spread to Europe through 2016 Sicily outbreak. This research describes race identification of Iranian isolates collected during the widespread distribution of stem rust in 2014-16. Purified urediniospores of 123 Pgt isolates were separately inoculated on seedlings of 20 North American differential wheat cultivars carrying different Sr resistance gene/s. Infection types were recorded at 14 days post inoculation (dpi) using Stakman et al. 0-4 scale. Based on the letter code nomenclature, we identified the Pgt races TKTTF, TTTTF, TTKSK, TTKTK, PKTTF, TKSTF, PKSTF, PKTTC, PTRTF, PTTTF, PKSTC, TTRTF, TKSTC and PKRTF in Iran. TKTTF and TTTTF were determined as prevalent Iranian Pgt races. This is the first report of race TTKTK, a new variant of Ug99 race group with virulence on Sr31 and SrTmp resistance genes, in Iran. Since TTKTK primarily occurred in south west of Iran, the migration route for this new race seems to be similar to race TTKSK. The high race variation observed in this study could indicate a high genetic diversity among P. graminis f. sp. tritici populations in Iran, as a wheat center of origin.
ICAR Indian Institute of Wheat and Barley Research, Karnal
Satish Kumar, Rekha Malik, Garima Singhroha, Vinod Tiwari, Gyanendra Pratap Singh
Breeding rust resistant cultivars using conventional methods is time-consuming, complex and slow, but molecular markers offer a rapid alternative for developing cultivars with improved disease resistance. Three wheat cultivars, DBW88, DBW107, and DBW110, from different production zones were used as recipients for incorporation of resistance genes using a marker-assisted backcross (MAB) breeding approach. Leaf rust resistance gene Lr32 is being incorporated into all the three varieties, stripe rust resistance gene Yr15 is being incorporated into DBW88 and DBW107, and stem rust resistance gene Sr26 is being added to variety DBW110. Lines PBW703 (Yr15), FLW15 (Lr32) and Avocet (Sr26) were used as donors. Six cross combinations viz., DBW88/PBW703, DBW107/PBW703, DBW88/FLW15, DBW107/FLW15, DBW110/FLW15 and DBW110/Sr26 were made at Karnal during 2015-16 and the crosses were grown at IIWBR-RS, Dalang Maidan for backcrossing. BC1F1 plants were raised at Karnal during 2016-17. Both foreground and background selections were practiced in each combination. SSR markers gwm264 and barc135 were used for foreground selection of Lr32, marker barc8 was used for selection of Yr15, and markers Sr26#43 and BE518379 were used to detect presence and absence of Sr26. From 90 to 127 polymorphic SSR markers chosen for each cross from an initial set of 800 screened on the parents are being used for background selection.
Ravi Singh, Karim Ammar
Stripe rust, caused by Puccinia striiformis tritici (Pst), continues its evolution towards virulence to race-specific resistance genes. Identification of Mexican Pst isolates MEX16-03 and MEX16.04 that changed infection types of Yr10 testers from 1 to 9 and for Yr24 (=Yr26) testers from 3 to 9 indicated that a mutation for virulence to these resistance genes has occurred in a predominant race detected in 2014 and maintained at CIMMYT as MEX14.191 and at INIFAP as CMEX14.25. Isolate MEX14.191 was responsible for the susceptibility of popular varieties Nana F2007 and Luminaria F2014 grown in central Mexican highlands. Isolate MEX16.04 has the following avirulence/virulence formula: Yr1, 5, 15, SP/Yr2, 3, 6, 7, 8, 9, 10, (17), 24, 26, 27, 28, 31, 32 using the Avocet near-isolines and other known testers. Virulence to Yr10 and Yr24 (=Yr26) were also confirmed by testing seedlings of cultivars Moro (Yr10), Chuanmai 42, and Neimai 836 (Yr24). Seedling tests carried on 200 bread wheat, 550 durum, and 460 synthetic hexaploid wheats with their respective durum parents from CIMMYT collection indicated that MEX16.03 and MEX16.04 do not represent a major threat because a majority of the lines remained resistant to these isolates. However, it is worth mentioning that durum cultivars, such as Khofa, Desert King, Anatoly, Movas, and Llareta INIA, and 10 primary synthetic hexaploid or synthetic-derived bread wheats that were resistant to MEX14.191 became susceptible to MEX16.03 and MEX16.04. Our results indicate that resistance gene Yr10 was absent and Yr24 occurred in low frequency in CIMMYT bread wheat germplasm. A majority of CIMMYT durum wheat possibly carried Yr24 in combination with other effective gene(s).
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.
Scuola Superiore Sant'Anna
Yosef G.,Kidane, Cherinet, Alem, Bogale, Nigir, Dejene, Mengistu, Carlo, Fadda, , , , , , , , , , , , , , , , , , , ,
The Ethiopian plateau hosts thousands of durum wheat landraces cultivated in low input agriculture conducted by an estimated 70 million smallholder farmers. Having thoroughly characterized the phenotypic and molecular uniqueness of Ethiopian durum wheat landraces, we produced a large nested association mapping (NAM) population harnessing their mostly untapped diversity in a set of recombinant inbred lines (RIL). The NAM founders are 50 landraces providing valuable traits such as drought tolerance and resistance to pests, and maximizing molecular diversity. Each selected landrace was crossed to a durum wheat line with an international background (Asassa), establishing independent interconnected bi-parental families, for a total of 6,280 RILs currently in F8. The Ethiopian NAM is at once i) a powerful QTL mapping tool that will side the increasing availability of genomic tools in wheat towards high-throughput candidate genes identification, and ii) a large pre-breeding panel closing the gap between local and international materials. Here we discuss the molecular and phenotypic characterization of twelve NAM families, represented by 100 RILs each. The 1,200 NAM RIL showed elevated allelic variation and a genetic structure reminiscent of the breeding design followed. The NAM RILs were phenotyped for ten agronomic and five disease traits in multiple locations in the Ethiopian highlands. A quantitative method eliciting smallholder farmers traditional knowledge was used to record local farmers appreciation of NAM RILs in all phenotyping locations. We report that the superior genetic properties of the NAM can be used to map QTL for both agronomic and farmer traits with unprecedented precision. The most promising NAM RILs can be identified combining farmers appreciation and agronomic measures, and prioritized for introgression of Ethiopian landraces traits in breeding pipelines aiming at higher uptake and productivity in local agriculture.
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
International Maize and Wheat Improvement Center (CIMMYT), P.K. 39 Emek 06511 Ankara, Turkey
Nilufer,Akci, Sridhar, Bhavani, Mesut, Keser, Fatih, Ozdemir, Ruth, Wanyera, Alexey, Morgounov, , , , , , , , , , , , , , , , , ,
A diverse set of winter wheat germplasm was screened for resistance to stem rust in large-scale trials in Kenya and Turkey during 2009-16. The study aimed to select resistant material and characterize types of resistance and possible genes, as well as evaluate agronomic traits and resistance to other diseases to select superior variety candidates and parental lines. The study material was comprised of various Facultative and Winter Wheat Observation Nurseries (FAWWON), which are developed and distributed by the International Winter Wheat Improvement Program (www.iwwip.org) in Turkey. More than 1600 global accessions were screened, with most evaluated for two years. Based on stem rust data from Kenya, more than 400 genotypes were identified exhibiting adequate levels of resistance to the Ug99 race group. The highest number of resistant lines originated from IWWIP (~170), USA (~100), Russia (~40), Iran (~30), Romania (~20), and South Africa (~20). Material was also tested at two sites in Turkey: Haymana (artificial inoculation) and Kastamonu (natural infection). There was no significant correlation between stem rust severities in Kenya and in Turkey, due to differences in stem rust pathotypes. However, a set of germplasm (more than 100 entries) has been identified as resistant in both countries. This set represents promising material as variety candidates and parental lines; another study is currently identifying the genes controlling the stem rust resistance in this population. IWWIP distributed stem rust resistant germplasm to its global collaborators during 2010-2015, in response to the threat from the Ug99 race group. New resistant germplasm combining broad adaptation, high yields, and resistance to other diseases is available on request.
Rosemary,Shrestha, Kate, Dreher, Victor, Jun Ulat, Luis A., Pubela Luna, Susanne, Dresigacker, , , , , , , , , , , , , , , , , , , ,
The Global Wheat Program of CIMMYT is one of the largest public breeding programs in the world consisting of millions of lines/ genotypes derived from thousands of crosses evaluated under using a shuttle breeding cycle and multi-environment testing. The germplasm is phenotyped for conventional (such as yield and grain quality) as well as non-conventional traits (physiological traits) in field and greenhouse conditions. The breeding germplasm is also screened with genome-wide markers (using Illumina SNP array, genotyping-by-sequencing, or DArTseq platforms) and/or multiple gene/QTL region-specific molecular markers (using KASP platform). All genotyped samples are registered in the "DNA SampleTracker," a software system for tracking DNA samples developed at CIMMYT. In collaboration with High Throughput Genotyping Platform project, the plant sample and data collection methods are optimized. Meanwhile, the extensive wheat genealogies and phenotypic information have been maintained in the International Wheat Information System and will be transferred to a new Enterprise Breeding System. Furthermore, several bioinformatics/statistical genetics methods with the objectives of gene discovery and genomic prediction have been developed and utilized for optimizing genomics-assisted selection. The wheat team is a member of "Genomic Open-source Breeding Informatics Initiative (GOBII)" which aims to develop and implement genomic data management systems to enhance the capacity of breeding programs. Under this initiative, a new genomics database has been built and a pilot wheat version is being tested at CIMMYT. Several decision support tools are also under collaborative development, such as a Genomic Selection Pipeline based on Galaxy, Flapjack-based F1/line verification, and marker assisted backcrossing tools. Additional tools are envisioned for the future including a Cross-Assistor and Selection-Assistor. The ultimate aim is to seamlessly connect the genomic database, phenotypic database, and decision support tools to support the breeding selection process and to lead to the development of cultivars with increased rates of genetic gain.
Institute of Agricultural Sciences, Banaras Hindu University, India-221005
Punam Singh,Yadav, Naveen Kumar, Umesh Chandra, Dubey, Ramesh Chand, Sundeep Kumar, Arun Kumar Joshi
Four leaf rust adult plant resistance genes (Lr34, Lr46, Lr67 and Lr68) are known to be associated with leaf tip necrosis (LTN). LTN caused by these genes is different from each other at phenotypic level. LTN associated with APR genes Lr34, Lr46 and Lr67 has been designated as Ltn1, Ltn2 and Ltn3. Seventy-seven CIMMYT genotypes were selected to find out the association between genotypic and phenotypic variability for LTN and its association with yield traits; 1000 grain weight, grain yield, leaf area and percentage of leaf tip necrosis in the flag leaf of main tiller. All the genotypes were screened for the presence of 3 APR genes with linked markers, csLV34 for Lr34; Xwmc44 and Xgwm259 for Lr46 and Xcfd71 for Lr67. The genotypes were grouped into 5 classes; only Lr34, only Lr46, only Lr67, Lr34+L46+Lr67 and genotypes lacking all three genes. Molecular analysis revealed that 7 genotype with Lr34 only, 6 with Lr46 only, 7 with Lr67 only, 13 with all the 3 genes, and 28 without any Lr gene. Phenotypic data of LTN percentage was compared and it was noted that maximum LTN % was observed for Lr67 (7.811%) followed by Lr46 (7.348%) and Lr34 (6.47%). Surprisingly, presence of all three genes reduced the LTN% (4.7055%) as compared with absence of all three genes (6.011%). It was also observed that the three genes simultaneously reduced 1000 grain weight and plot yield. All three genes increased leaf area highly significantly both when they are alone or together (34.7 to 44.7 cm2) in comparison to those genotypes (24.7 cm2) which lacks these Lr genes and also reduced 1000-grain weight and plot yield but non-significantly.
Muhammad,Noor, Makhdoom, Hussain, Majid, Nadeem, Monsif, ur Rehman, Jesse, Poland, Ravi, Prakash Singh, Matthew, Reynolds,, , , , , , , , , , , , , , , ,
Drought and heat along with rusts are the most common biotic and abiotic stresses that affect growth, development and yield of wheat crop in Pakistan. CIMMYT in partnership with Wheat Research Institute Faisalabad (WRI-Fsd), USDA, and Kansas State University initiated an effort to develop heat tolerant, high yielding, and farmer-accepted rusts resistant wheat varieties for Pakistan. A set of 1656 wheat lines received in the form of EPCBW and SABWGPYT nurseries were tested in 2013-14 and 2014-15 wheat season, respectively. Testing of the materials at (WRI-Fsd), Pakistan under normal and late planting conditions resulted in the selection of 55 lines with higher grain yield and resistant to both leaf (LR) and yellow (YR) rusts. Among these lines, the line no. 1027 produced maximum yield (5.78 ton/ha) under normal and line no. 5030 produced maximum yield (3.38t/ha) under late planting conditions with resistance to both LR and YR. Further evaluation of the selected 55 lines as HYT-60 in 2015-16 showed the average grain yield ranged from 4.98 to 2.51 ton/ha under normal and 1.74 to 0.73 t/ha under late planting. Three lines HYT-60-57, HYT-60-7 and HYT-60-5 were included in the first year advanced yield trials to test for their potential as commercial cultivars while another seventeen lines were distributed as HYT-20 to six national wheat breeding programs for yield testing at key location which will enable national partners to combine yield potential with resistance to biotic and abiotic stresses.