Seed & Plant Improvement Institute (SPII), AREEO, Karaj, Iran
Ramin Roohparvar, Safarali Safavi, Gholamhossein Ahmadi
In recent years, wheat stem rust, caused by Puccinia graminis f.sp. tritici, has been reconsidered in Iran due to its prevalence and the emergence of the dangerous Ug99 race. This study was conducted to understand pathogenic variation in the population of P. graminis f.sp. tritici, detection of effective genes, and identification of resistance in Iranian commercial wheat cultivars or advanced lines, by planting stem rust trap nurseries under natural disease infection in several regions of Iran during the 2016-2017 cropping season. The trap nursery in each location included 48 wheat lines each carrying a single gene of stem rust (Sr) resistance, seven lines each carrying Sr multigenes, eight additional lines to confirm four Sr genes, 149 commercial wheat cultivars or advanced lines from Iran, plus several susceptible checks. The percentage leaf area affected (disease severity) and infection type were recorded at adult plant stage when disease was well developed on flag leaves of susceptible checks. Results showed presence of virulence for several Sr genes in one or more locations. However, the single genes of Sr13, Sr23, Sr24, and two complex genes of Sr7a+Sr6+Sr12 and Sr6+Sr24+Sr36+Sr1RS-Am were still effective against stem rust in all locations. The results of evaluations of commercial wheat cultivars or advanced lines showed that approximately 16% the genotypes tested including wheat cultivars Gonbad, Shiroudi, Chamran-2, Baharan, Dena, Karkheh, and Arya were resistant in all locations.
Plant Pathology Research Institute
Atef Shahin, Mohamed Abu Zaid
Resistance genes Sr2, Sr22, Sr24, Sr25 and Sr26 confer adult plant resistance to Pgt race TTKSK (=Ug99). Ten Egyptian wheat varieties and four bread wheat entries from CIMMYT were screened with five DNA markers to determine the presence of these genes, and were evaluated for stem rust response at Sakha and Sids during the successive growing seasons of 2015/16 and 2016/17. Varieties Giza 171, Sakha 94, Gemmeiza 11, and CIMMYT lines 6043, 6091, 6107 and 6197 were resistant with severities ranging from TrR to 5MR/MS. Sr2 was present in all entries; Sr24 was present in one local Egyptian cultivar (Misr2); Sr25 was present in Misr 1, Misr 2, Gemmeiza 9, Gemmeiza 11, and lines 6091 and 6197; and Sr26 was present in line 6197.
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.
USDA-ARS, Pullman, WA, USA
Lu Liu, Meinan Wang, Junyan Feng, Deven See, Shiaoman Chao
Stripe rust, caused by Puccinia striiformis f. sp. tritici, is the most destructive disease of wheat in the US Pacific Northwest. Durable high-temperature adult-plant (HTAP) resistance to stripe rust has been emphasized for breeding wheat cultivars and the resistance level has been gradually increased since the early 1960s. Wheat cultivar Madsen has been widely grown, intensively used in breeding programs, and has exhibited durable and high level resistance to stripe rust since its release in 1988. To map its resistance genes and determine the genetic basis of durable and high-level of resistance, Madsen was crossed with susceptible cultivar Avocet S, and 156 recombinant inbred lines (RILs) were developed. The RILs and parents were tested with races PSTv-37 and PSTv-40 in seedling stage at low temperatures in the greenhouse and in adult-plant stage in the fields of Pullman and Mount Vernon, WA in 2015 and 2016 under natural infection of the pathogen. The RILs were genotyped with single-nucleotide polymorphism (SNP) markers derived from genotyping by sequencing and the 90K Illumina iSelect wheat SNP chip. A linkage map was constructed with 1,348 SNP loci. QTL analysis identified three genes for all-stage resistance on chromosomes 1AS (QYrMad.wgp-1AS), 1BS (QYrMad.wgp-1BS), and 2AS (QYrMad.wgp-2AS); and two QTL for HTAP resistance on 3B (QYrMad.wgp-3B) and 6B (QYrMad.wgp-6B). QYrMad.wgp-2AS was the most significant QTL, explaining 16.03-71.23% phenotypic variation depending upon the race or environment, followed by QYrMad.wgp-6B that was consistently detected in all field experiments and explained 6.7-35.9% of the phenotypic variations. Based on the chromosomal locations and the results from other studies, QYrMad.wgp-2AS contains Yr17 and a HTAP resistance QTL, and QYrMad.wgp-1AS is a new QTL. The interactions among these QTL were mostly additive. The combination of the five QTL for different types of resistance provides the durable and high level resistance to stripe rust.
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.
Ethiopian institute of agricultural research
Dr. Netsanet B. Heyi, Dr. Getaneh W. Wolderufael, Tsegab T.
Stem rust caused by Puccinia graminis f. sp. tritici (Pgt) is a major production constraint in most wheat growing areas of Ethiopia. The stem rust pathogen is capable of rapidly developing new virulence to resistance genes. The highlands of Ethiopia are considered a hot spot for Pgt diversity. The present study was conducted to investigate the virulence diversity and spatial distribution of races of Pgt in the major wheat growing areas of Ethiopia. The physiologic races of Pgt were determined on seedlings of the standard wheat stem rust differentials following the international system of nomenclature. Stem rust race analyses were carried out both at Ambo Plant Protection Center and the Cereal Disease Laboratory in Minnesota. 426 stem rust samples were collected from major wheat growing of the country in the 2016 cropping season and 185 viable samples were analyzed. Stem rust races TKTTF, TTKSK, TTTTF, JRCQC and RRTTF were identified. Among the identified races, TKTTTF was dominant at a frequency of 78.7% followed by TTKSK (10.6%). Race TTTTF was found for the first time in Ethiopia in 2016. Only one resistance gene in the differential set, Sr24, was effective against all isolates. Stem rust resistance gene Sr31 was found to confer resistance to most of the races prevalent in Ethiopia with the exception of Ug99. Sr24 could be used in combination with other resistance genes in breeding for resistance to stem rust in Ethiopia.
University of Minnesota
Caixia Lan, Ravi Singh, Matthew Rouse, Muhammad Imtiaz, James Anderson
The rapid appearance of new races of rust pathogens with virulence for the major seedling resistance genes in wheat has intensified the focus to discover adult plant resistance (APR) genes in wheat and utilize them in breeding programs for sustainable wheat production. The experimental breeding line 'Copio' developed by the International Maize and Wheat Improvement Centre (CIMMYT) in Mexico has exhibited high levels of APR to all three rusts including the African stem rust Ug99 race group. To dissect the mechanism of APR in Copio it was crossed with APAV#1, which is susceptible to all three rusts and a population of 176 F4:F5 recombinant inbred lines (RILs) was developed at CIMMYT. Both parental lines were found to be susceptible (IT >3) at the seedling stage to races TTKSK and TKTTF, which ensures the field data from Africa will be applicable for APR mapping. Seedling tests were also conducted on the RIL population using the predominant Pakistani race RRTTF, and Chi-squared tests indicated segregation of two stem rust seedling genes (?2 test P value of 0.00002). Both parents were also tested for the known APR genes Lr34/Yr18/Sr57, Lr46/Yr29/Sr58, Lr67/Yr46/Sr55 and Sr2/Yr30 using molecular markers and results indicate that APAV#1 does not carry any known APR genes, while Copio might have Lr46 and Sr2. This population was tested in four field environments (US, Pakistan, Mexico, and Kenya) for leaf, stem and yellow rusts during 2015-16 and 2016-17. Disease severity distributions of all three rusts for the RILs across all environments were continuous, suggestive of quantitative and polygenic resistance.
We are using genotyping by sequencing (GBS) as a genotyping platform and anticipate having preliminary mapping results available by spring 2018.
University of Seville
Solis,Ignacio, , , , , , , , , , , , , , , , , , , , , , , , , , , ,
Leaf rust is an important worldwide disease on wheat caused by the fungus Puccinia triticina. Great infections on durum wheat occurred in Southern Spain in the 2000s but diminished in recent years due to deployment of resistant varieties and application of fungicides by farmers. A leaf rust survey was carried out from the 2009-15 period to monitor the virulence spectrum of the prevailing pathotypes. A total of 84 leaf rust isolates were collected on durum wheat fields. From those, single culture were obtained and used to inoculate a set of 27 differential isolines of the susceptible variety Thatcher. In addition 8 durum varieties with known Lr genes were also included.
The main highlight is that the resistance conferred by the popular Lr14a gene was broke up in 2013, but since then virulence to this gene is not widespread. In total, 23% of the isolates were virulent to the lines containing Lr14a. Lr1, Lr3, Lr3bg, Lr16, Lr24, Lr26, and Lr28 are very effective. Lines carrying Lr2c, Lr10, Lr14b, Lr20, Lr23, and LrB displayed susceptibility to most isolates. The durum varieties Jupare (Lr27+Lr31), Guayacan (Lr61), Storlom (Lr3+) and Camayo (LrCam) are also resistant against all isolates tested. Diversification of Lr genes is needed in the coming varieties to delay the appearance of new virulent races.
Jianping Zhang, Peng Zhang, Robert Park, Narayana Upadhyaya, Robert McIntosh, Sambasivam Periyannan, Brande Wulff, Burkhard Steuernagel, Evans Lagudah
Evolution of rust pathogens continues to pose challenges to global wheat production. Major resistance (R) genes, which encode proteins of the NBS-LRR (Nucleotide-binding site, leucine-rich repeat) family, have been a valuable resource for breeders to minimise yield losses from infection. Many wheat varieties harbor numerous R genes that could be identified and cloned in order to engineer more sustainable disease control. The advent of targeted gene enrichment and next-generation sequencing (NGS) has allowed rapid cloning of specific R genes, thus enhancing efforts to pyramid these genes and investigate their underlying resistance mechanisms. Several R genes present different phenotypes in certain genetic backgrounds, and cloning them would be an important step towards uncovering their interactions. Hybrid necrosis is one such phenotype observed in crosses of wheat genotypes involving the R gene Lr13 and complementary genes, Ne1 and Ne2, occurring in different allelic forms. It was recently concluded that Lr13 and an allele of Ne2 are actually the same gene based on genetic and mutational studies. The capability of Lr13 to confer both leaf rust resistance and hybrid necrosis cannot be answered without first cloning it. The lack of tightly linked markers coupled with the proximal 2BS chromosomal location of Lr13 does not make it easily amenable to map-based cloning. The NGS-based pipeline MutRenSeq (mutagenesis and R-gene enrichment sequencing) was used on EMS (Ethyl methanesulfonate) induced, susceptible Lr13 mutants along with support from comparative genomics to ascertain candidate gene sequences for Lr13, which are at advanced stages of screening and confirmation. Definite proof that a single gene is involved will only come with transformation studies when the cloned Lr13 candidate transformed into a susceptible line confers both a resistance phenotype in the transgenic line and a necrotic phenotype in the offspring of crosses between the transgenic line and a line possessing Ne1.
Sathguru Management Consultants
Kanan,Vijayaraghavan, Vijay, Paranjape, Richa, Kapur, Vignesh, Vilayanur Jayaraman, , , , , , , , , , , , , , , , , , , , , ,
Wheat is one of the most important food crops of the world. India is the second largest producer of wheat, currently producing 95 million tons from about 30 million hectares. Looking ahead to 2050, India needs to constantly increase production to about 150 million tons, to meet the rising population and demand. With area under cultivation having no room for growth, productivity will be the main pillar for growing production. Currently India?s yield of 3.1 t/ha has plenty room for growth as compared to the world leaders such as France (7.5 t/ha), Germany (7.3 t/ha) and UK (6.6 t/ha). Wheat productivity depends on multiple factors, seed being one of the most important.
The current operating environment is characterized by wheat R&D in the country conducted by public institutes, but there are clear signs of an emerging private sector involvement. The government promoting Inter-institutional linkages by way of associating private players in research and seed production.
This study evaluates and reflects on the current situation of the wheat seed sector in India - from research, variety/hybrid development, seed production, indent to distribution, the players involved, the challenges therein, upcoming technologies and the way forward.