Filippo,Bassi, Rodomiro, Ortiz, Ibrahima, Ndoye, AbdelKarim, Filali-Maltouf, Bouchra, Belkadi, Miloudi, Nachit, Michel, Baum, Hafssa, Kabbaj, Habibou, Gueye, Madiama, Cisse, , , , , , , , , ,
Wheat is a major food crop in West Africa, but its production is significantly affected by severe heat. Unfortunately, these types of high temperatures are also becoming frequent in other regions where wheat is commonly grown. In an attempt to improve durum wheat tolerance to heat, a collection of 287 elite breeding lines, including several from both ICARDA and CIMMYT, was assessed for response to heat stress in two irrigated sites along the Senegal River: Fanaye, Senegal and Kaedi, Mauritania during 2014-2015, and 2015-2016 winter seasons. The maximum recorded grain yield was 5t ha-1, which was achieved after just 90 days from sowing to harvesting. Phenological traits (heading, maturity and grain filling period) and yield components (1000-kernel weight, spike density and biomass) had also large phenotypic variation and a significant effect on grain yield performance. This panel was genotyped by 35K Axiom to generate 8,173 polymorphic SNPs. Genomic scans identified a total of 34 significant association between single nucleotide polymorphisms (SNPs) and traits across the four environments, including 15 related to phenological adaptation, 12 controlling grain yield components, and seven linked to grain yield per se. The identification of these genomic regions can now be used to design targeted crosses to pyramid heat tolerance quantitative trait loci (QTL), while the SNPs underlying these QTL can be deployed to accelerate selection process facilitated by DNA-aided breeding.
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.
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.
University of the Free State
Gerrie Booysen, Willem Boshoff, Jozua Joubert
Urediniospores of rust fungi can be applied to cereal plants in several ways. Depending on the objective and available infrastructure, plants can be inoculated with a suspension of spores in either water, light mineral oil (e.g. Soltrol 130®) or engineered fluid (e.g. Novec 7100®). Alternatively, dry spores can be allowed to settle on plant surfaces by dusting or directly applied with a spatula or small brush. Several rust laboratories employ a system where a spore-oil suspension, contained in a gelatin capsule, is sprayed onto seedling leaves by means of a dedicated atomizer connected to an air pressure source. Although this approach is easy to use and highly efficient, the devices are not commercially available in South Africa. Locally, these inoculation appliances need to be manufactured by a conventional milling process that requires a specialized workshop and skilled personnel. This subtractive process is labour intensive and greatly prohibitive in terms of costs. Using a process called Additive Manufacturing (AM), also known as "3D printing", the body of an inoculator was digitally designed and then laser sintered in nylon. Loose powder was removed from flow channels by compressed air. A copper tube fitted afterwards connected the nylon body with the spore suspension in the capsule. Replicated inoculation tests of wheat seedlings with urediniospore bulks or single pustule collections of Puccinia triticina and P. graminis f. sp. tritici resulted in consistent levels of rust severity and infection frequency. Cleaning of inoculators in acetone for 1 min followed by a 1 h heat treatment at 60°C produced no contaminant infection in follow-up tests. The design has been registered in South Africa, the USA and Europe.
National Agronomic Institute of Tunisia
Sana Kamel, Elhem, Elfahem, Wissal Feriani, Hanen Sbei
In order to identify sources of resistance to tan spot caused by Pyrenophora tritici-repentis, 359 local wheat accessions were evaluated for reaction to the Oued-Mliz isolate in controlled conditions and in the field. Two and three assessments were carried out at the seedling and adult stages, respectively. There was a highly significant accession effect and 4.2% of accessions were highly resistant in both controlled conditions and the field. Assessments at the seedling stage were positively correlated with each other, and assessments in the adult stage were also positively correlated. However, assessments at the seedling stage were negatively correlated with those at the adult stage. One hundred and fifty five accessions with known origins (from 15 localities belonging to four districts) were projected on a graph defined by the two axes: reactions at the seedling stage and reactions at the adult stage. After placing the average reactions at the seedling and adult stages on the graph, four groups of accessions were obtained: accessions that were resistant to both stages, accessions that were resistant at the adult stage only, accessions that were resistant at the seedling stage only, and accessions that were susceptible at both stages. All four groups were found in each district. However, considering localities, reactions of accessions were highly variable. For example, accessions originating from Menzel Hbib were genetically variable and were represented in each of the four groups, whereas accessions from Sidi El Hani were all resistant at both stages. Further work is needed to study the genetic variability within and between localities and to better understand the resistant accessions.
University of Hohenheim, Germany
Afrem,Issa, Helim, Youssef, Nawzad, Suleiman, Abdul Rahman, Issa, , , , , , , , , , , , , , , , , , , , , ,
Wheat is grown in Syria during the November-December. Wheat is exposed to many strains that negatively affect its productivity especially rust diseases, which was reported on wheat in Syria for many years and the most severe in 2010, Therefore, we studied the effect of planting dates on the severity and development of yellow rust disease. Where the field trials of the 2010-2011 season were carried out at the two locations in northeastern of Syria: Al-Qamishli Research Center and Yanbouh Research Station in Al-Malekia. By cultivating the susceptible bread wheat Cham 8, where six dates were planted starting from 02.10. 2010, a difference of 15 days. The results showed there was a difference in the severity of the yellow rust disease according to the dates of cultivation and thus the stages of growth in the plant and this was evident in the Yanbouh location where the onset of the onset of injury on 08.04.2011 in the all dates and developed the infection to 40S degrees and 30%. Also, on the 24. 04. 2011, the infection was recorded at the Qamishli location only on the third and fourth dates. The disease did not develop more than 10S and 10% due to climatic conditions due to rain and high temperature during the season. The results showed a positive correlation between the evolution of the disease and vegetative growth of plants, where the growth of plants was more active at the site of Yanbouh, especially in the second, third and fourth dates in the development of infection on plants in the rest of the dates because of weak and slow growth of plants.
Ayele Badebo, Abebe Atilaw, Habtemariam Zegeye, Zerihun Tadesse, Wasihun Legesse, Terefe Fitta, Dawit Asnake
In Ethiopia, quality seed of improved varieties is the least expensive and most critical input for the sustainable production of wheat, a strategic food security crop grown by some 4.7 million households on 1.7 million hectares. Because wheat is self-pollinated, farmers can save and replant seed from their harvests for several years, without the variety losing its genetic identity. At the same time, recommended seed rates for wheat (150 to 200 kilograms per hectare) are significantly higher than those for tef (15 kg/ha) or maize (25 kg/ha), so some 255,000 tons of seed is required to sow Ethiopia's entire wheat area each year. Most of this still comes from informal seed systems; only four seed enterprises (ESE, ASE, OSE and SNNPSE) currently produce certified seed of various crops and they lack the capacity to supply enough high quality seed for the nation's approximately 20 million households. In collaboration with the Ethiopian Institute of Agricultural Research (EIAR) and through the USAID-funded project "Seed multiplication and delivery of high-yielding rust resistant bread and durum wheat varieties to Ethiopian farmers," the International Maize and Wheat Improvement Center (CIMMYT) is working to increase wheat farmers access to affordable, certified seed of improved varieties that are high-yielding and also feature durable resistance to the rust diseases. Approaches pursued include the fast-track evaluation and release of improved varieties, the pre-release or accelerated seed multiplication of released wheat varieties through formal and informal seed systems, and demonstrations and scaling up of improved wheat varieties. This paper describes best practices to address seed shortages faced by wheat farmers in 53 woredas.
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 Georgia
Mohamed,Mergoum, Yuanfeng, Hao, Jerry, Johnson, Dan, Bland, James, Buck, John, Youmans, Benzamin, Lopez, Steve, Sutton, Zhenbang, Chen, , , , , , , , , , , ,
Leaf rust disease, caused by the fungal pathogen Puccinia tritcina, is the most destructive foliar disease of wheat worldwide. Gene combination of Lr37/Yr17/Sr38 has been used in Georgia (GA) to prevent the loss from leaf rust; however, with the emergence of new virulent races, these genes have lost their effectiveness. 'AGS 2000' and 'Pioneer 26R61' are the most common soft red winter wheat (SRWW) cultivars in Southeastern US, and have been used as good sources of resistance to leaf and stripe rusts, and powdery mildew. To characterize the genetic basic of resistance of AGS 2000, a mapping population of 178 recombinant inbred lines (RIL) has been developed from a cross with Pioneer 26R61. This population was genotyped using a combination of SSR, DArT, and SNP markers, and a total of 2734 markers covering the entire genome were used for the construction of genetic map. Phenotypic evaluation of parents and RIL population was conducted at the seedling stage using a virulent GA leaf rust race. QTL mapping revealed a major QTL on chromosome 2BL, explaining about 20% of total phenotypic variation in AGS 2000. Additionally, a minor QTL was also detected on chromosome 5B. QTL on 2BL was identified as a novel gene, and can be used in marker-assisted selection for leaf rust resistance.
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.