North Dakota State University
The rapid adoption of new varieties of wheat with disease resistance is critical to mitigating losses due to new diseases or disease races, even when only part of an integrated disease management program may include fungicides. There are numerous sources of information that can be used by farmers in North Dakota when selecting varieties with specific disease resistance as well as other traits. Formal surveys were conducted to determine the role of extension activities on the adoption of Fusarium Head Blight (FHB) control practices especially on the use of new varieties with FHB resistance. This disease became a regular and devastating problem of small grains in eastern North Dakotas in the 1990s. In a survey specific to North Dakota conducted in 2010, most respondents indicated that information from the extension service was their main source of information for FHB control with varietal selection their primary means of control. Extension publications, accessed through the internet or as hard copy obtained from an extension office or at an extension meeting were the most important sources; fewer respondents obtain their information from extension meetings and field days. A survey conducted in 2014 found that private sources (consultants and input suppliers) are becoming more important sources of information for FHB control and varietal selection, perhaps because the disease has become better understood and most new varieties have some level of FHB resistance. In durum wheat, where there are few varieties available from the private sector, extension publications were found to be the main source of information used for selecting new varieties. Data from these surveys show the importance of a strong and active extension program in ensuring that new varieties with resistance to new diseases/disease races are readily adopted.
Wheat Research Institute, Ayub Agricultural Research Institute,Faisalabad,Pakistan
Javed Ahmad, Ghulam Mehboob Subhani, Makhdoom Hussain
Crops vary greatly in their tolerance to heat stress. Among the major staples wheat is considered the most sensitive. Wheat production is severely threatened in many countries by heat stress especially during reproductive and grain-filling stages. For recent decades due to change in global climate, the qualitative and quantitative yield of wheat is affected. To meet the demand of food requirements of ever increasing population there is a need to develop varieties which can tolerate heat stress for which screening of germplasm is pre requisite. In the present study, 30 genotypes were used to check their response to heat stress using randomized complete block design following two different sowing dates. Analysis of variance and multivariate analysis were used for finding important traits and best genotypes in relation to heat stress. High broad sense heritability coupled with high genetic advance was measured for gluten and zeleny indicating the presence of additive gene effect for these traits. Principal component analysis showed that under heat stress conditions genotype 11, 14, 15, 20 and 30 performed well. These genotypes were also found resistant to yellow and brown rust and can be used in further breeding programs for development of heat tolerant, rust resistant genotypes.
Hawassa Agriculture Research Centre
Agdew Bekele, Waga Mazengia, Shimekt Maru
Shortage of seed of rust resistant varieties is a challenge of small holder farmers in wheat production. To successfully address this issue, one of the essential elements in wheat production system is farmer's access to quality seed of improved varieties. This paper presents the experience of on-farm basic and pre-basic seed production of newly released rust resistant wheat varieties. For the first time in the country, On-Farm basic and pre-basic seed production of wheat varieties was carried out in two districts/woredas (Silti and Soddo) of two specific locations (Loke faka and Wacho) where the Edget Farmers' Seed Multiplier and Marketing Union was licensed to produce some crop varieties (cereals and pulse), beginning in the 2011/2012 cropping season. Model farmers from primary cooperatives were selected based on the past experience they had with the union in producing certified seed. Selected farmers and relevant experts were trained on how earh seed of wheat is produced. Accordingly seed multiplication of four wheat varieties was conducted with frequent monitoring and evaluation at the course of multiplication.
As a result sufficient and quality basic seed of newly released wheat varieties was produced on-farm in both Loke and Wacho locations for own utilization and seed market. The result of the experiment revealed that it was possible to multiply quality wheat seed provided that partnership (with GOs and/or NGOs) is well-built and cooperative farmers do farm management practices as per the recommendations. On-farm seed production can be sustainable if the strong partnership exists among stakeholders, and wheat seed growers are given premium prices for their seed which is supported by the legal frame work that encourages the seed production of early generations. More importantly, the result of this experiment has a useful implication on government policies and strategies and government institutions' practice on farm early seed generation production and marketing.
National Agronomic Research Institute of Algeria
Among the many biotic constraints to wheat production in Algeria, rusts and in particular yellow rust (Puccinia striiformis), are among the most prevalent diseases that occur mostly all over the northern part of the country. Yellow rust has become now sporadic due to the exploitation of effective resistant genes in different forms and combinations (from CIMMYT and ICARDA). Earlier, durable resistance was probably due to many genes, such Yr18, Yr9, Yr27 and Yr1.
Yellow rust appeared as epidemic in 2004, over 600 000 ha of bread wheat ; severity exceeded 70%. Yields from affected fields of Hidhab a susceptible variety did not exceed 5.2 q/ha, while resistant cultivars yielded up to 48 q/ha. Monitoring of the pathogen virulence factors and their changes provides basic information for the development of an early warning system. This experiment was carried out in 5 Eastern Algeria locations. 30 lines of a standard set of yellow rust and 14 near-isogenic lines from ICARDA were sown in 2-m rows in 2014 and 2015. According to the results, virulence on Heines Kolben (Yr2), Kalyansona (Yr2), Lee (Yr7), Avocet R (YrA), Federation*4/Kavkaz (Yr9), Yr6/6*Avocet ?S?, Yr7/6*Avocet ?S?, Yr9/6*Avocet "S", Yr17/6*Avocet "S", TP1295 (Yr25) and YrSU was common during those two seasons. The frequency of virulence on plants with Yr2, Yr6, Yr7, Yr9 or YrA and Yr27 was up to 80%. No virulence was observed on plants with Yr1, Yr3, Yr4, Yr5, Yr8, Yr10, Yr15 and Yr18 genes. This material was extensively used in our breeding programs and several new cultivars are in the on farm trials where a participatory selection approach is used. All resistant and performing new varieties are being spread for replacement of most old susceptible ones.
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.