Institute of Phytopathology and Biodiversity, Batumi Shota Rustaveli State University, Georgia
Stem rust is a major threat to wheat production in Georgia. Breeding for resistance to the rusts is a major strategy for wheat improvement programs. Our objective was determination of the stem rust resistance levels in entries of the 4nd International Winter Wheat Stem Rust Resistance Nursery. Responses of 85 varieties/lines were evaluated in an inoculated field nursery. A coefficient of infection (CI) and area under the disease progress curve (AUDPC) were estimated for each entry. Fifteen entries (T03/17, TAM-107/T21, SD92107-2/SD99W042, KS95U522/TX95VA0011/F1/JAGGER, AR800-1-3-1/NW97S320, FL9547/NC00-14622, FL9547/TX00D1626, TAM302/KS93U450, MCCORMİCK/TREGO, NC00-14622/2137, TAM200/KAUZ//GOLDMARK/3/BETTY, KS920709-B-5-1-1/BURBOT-4, AFINA SOMNEZ, TAM200/KAUZ/4/BEZ/NAD//KZM(ES85.24/3/F900K) were resistant; 39 showed moderate resistance; 15 were scored MR-MS and 17 were moderately susceptible. Most of entries had very low CI (0.2 - 0.5) and AUPDC (less than 10.0); the best including T07/08, T07/09, T08/02, T08/01, T08/02, T08/04, CAKET/PEHLIVAN, ID800994.W/VEE//PIOPIO/3/MNCH/4/FDL4/KAUZ, PBI1013.13.3/3233.35 /3/STAR//KAUZ/STAR, DULGER-1//VORONA/BAU, ZANDER-17/3/YE2453/KA//1D13.1/MLT, 55-1744/7C//SU/RDL/3/CROW/4/MILAN/5/ITOR, 1D13.1/MLT//TUI/3/S?NMEZ/4/ATAY/GALVEZ87, TAM107//ATAY/GALVEZ87, HBF0290/X84W063-9-39-2//ARH/3/LE2301, STAR/BWD/3/PRL/VEE#6//CLMS, FRTL//AGRI/NAC/3/KALYOZ-17, CV. RODİNA/AE.SPELTOİDES10 KR, TAM 107//ATAY/ GALVEZ87, and 06393GP1. The severities for susceptible entries varied from 20 to 70%, with checks Morocco and Bezostaya 1 at 80% and 60%, respectively. However, the majority of entries (94%) had average CI of 0.2 - 20 and five entries with CI 21 - 40 had high to moderate levels of resistance.
Cereal Pathology Unit, Department of Cereal Research, Seed and Plant Improvement Institute (SPII), Iran
Resistance is an effective and economic method of controlling wheat stem rust provided the resistance gene(s) remains effective. We studied the stem rust responses of 372 synthetic hexaploid wheats (SHW) originally from CIMMYT under natural field infection conditions at Kelardasht, a stem rust hotspot. Stem rust severities were recorded using the modified Cobb scale prior to harvest ripeness. Seventy six and 17% of the genotypes (93% in total) were scored susceptible or moderately susceptible, whereas only 5 and 2% (7% in total) were moderately resistant or resistant, respectively. Based on our results, 26% of the genotypes were considered to have resistance, displaying field responses of 40MS to 20MSS. Those SHWs resistant to local Pgt races at Kelardasht could be used as sources of resistance in Iranian wheat breeding programs. Race analysis of Pgt isolates from the trials and seedling response tests on the entire SHW set are in progress.
Department of Plant Pathology, University of Minnesota, USA
Plant pathogens elicit host transcriptome changes that facilitate hyphal infection and proliferation throughout host tissues. Host genes targeted by the pathogen to facilitate infection have been identified as susceptibility genes (S-genes). As biotrophic pathogens, rust fungi must infect the host to obtain nutrients while suppressing defense responses and likely target host-derived genes to aid in this process. To further understand the host-pathogen interaction RNA-seq analyses were performed on three compatible host-rust pathogen systems: barley cv. Morex was inoculated with Pgt race TTKSK (Ug99), soybean cv. Williams 82 was inoculated with a field collection of Phakopsora pachyrhizi, and maize cv. B73 was inoculated with an isolate of P. sorghi collected at St. Paul. Differential expression was characterized at 6, 12, 24, and 72 h post inoculation. Homologous and differentially expressed host genes were identified and compared for similarities in patterns of differential expression. In each system, a transmembrane nitrate transporter was identified as significantly upregulated early in the interaction compared to mock inoculated controls. Transporters with this molecular function were previously correlated with altering the host-pathogen interaction by knockdown and knockout mutants that were associated with resistance and heightened expression was associated with enhanced susceptibility. The transporter identified in barley was chosen for analysis to understand its effect on the host-pathogen interaction. Current objectives include site directed mutagenesis utilizing multiplexed CRISPR/Cas9 constructs to induce knockout host alleles.
National Institute of Agricultural Research, INRA, Morocco
Bread wheat is the most important staple crop in Morocco. However, the low national production represents less than 50% of national need. Yellow (stripe) rust (Pst) and Septoria tritici blotch (STB) are the most important foliar diseases limiting bread wheat production in Morocco. The objective of this study was to identify effective sources of resistance to Pst and STB and to select candidate lines displaying high yield and resistance traits. A total of 194 bread wheat accessions provided by ICARDA and CIMMYT were evaluated during 2014 for grain yield and reaction to STB and yellow rust. The field trials were carried out at Douyet station, a key Moroccan rainfed location, and were arranged in a replicated complete block design of 3 replicates. For rust, each entry was scored using the modified Cobb scale when the susceptible check had reached 60S. The Saari Prescott scale was used to score STB reactions. The crop season was characterized by early and late drought associated with high temperatures after flowering. About 50% of accessions (99) showed high yields ranging from 1% to 55% above the highest national check, Arrehane (1.86 t/ha). About 48% (93 accessions) were highly resistant to moderately resistant to yellow rust and about 84% (164 accessions) were resistant to moderately resistant to STB. Overall, about 30% (58 lines) of accessions were high yielding with final disease severities ranging from 0-10% for yellow rust and from resistant to moderately resistant for STB. This group incorporates potentially valuable traits beneficial for our wheat breeding program. QUAIU*2/KINDE was the most promising accession with the highest grain yield (2.9 t/ha) combined with foliar disease resistance. Further multi-environment screening and field evaluations are required before recommending accessions for potential release.
Department of Crop and Soil Sciences, Washington State University, USA
Stripe rust (Puccinia striiformis f. sp. tritici) is a devastating disease of wheat production world-wide. Yr5 is a race-specific resistance gene effective to all races which have been identified in the U.S. Therefore, it has been increasingly used for cultivar development in the U.S. The goal of this study was to identify “breeder friendly” SNP markers associated with Yr5 through linkage mapping in a spring wheat recombinant inbred line (RIL) population and validate these markers with an additional RIL population, Pacific Northwest (PNW) wheat elite breeding materials, and a world-wide collection of spring wheat. RIL populations were developed from a cross between moderately susceptible experimental line WA8149 and two elite Yr5 donors, S0900317 and S0900163. Seventy PNW spring and winter wheat lines either carrying Yr5 or not, and 3,040 hexaploid spring wheat lines from a world-wide collection were used to further validate flanking markers for Yr5. Seedling resistance response to isolates Pstv-37 and Pstv-51 was evaluated for these RIL populations. These RILs were genotyped with 46 KASP markers located on chromosome 2B in addition to previously reported Yr5 linked markers, wmc175 (Murphy et al. 2009) and TaAffix65234.1.S1_at (McGrann et al. 2014). Linkage mapping was conducted by MapDisto v1.7.5. A total 10 markers localized Yr5 within 0.7 cM chromosome region in the WA8149/S0900317 population of 300 RILs. The same set of markers also localized Yr5 within 3 cM chromosome region in the WA8149/S0900163 population of 274 RILs. Newly identified KASP markers were closer to Yr5 than wmc175 and TaAffix65234.1.S1_at in these two populations. These markers were further validated with PNW winter and spring wheat and a world-wide collection of spring wheat. These KASP markers flanking Yr5 reliably selected for germplasm carrying Yr5 and will assist in pyramiding different resistances into breeding lines to develop more durable stripe rust resistant cultivars.
Program Director and Judging Panel Chair, Texas A&M University, USA
Monsanto’s Beachell-Borlaug International Scholars (MBBIScholars) Program was established on March 25, 2009, on Dr. Norman Borlaug’s 95th birthday. Monsanto initially funded the program for $10 MM ($2 MM per year for 5 years) and extended the program with a second grant for $3 MM ($1 MM per year for 3 years). As of February 2015 (6 years of funding) the program has supported 70 students. The 70 MBBIScholars were selected from 359 applications. MBBIScholars are from 25 countries with India having 20 scholars. MBBIScholars from other countries are – Argentina 3, Bangladesh 2, Brazil 2, China 4, Columbia 4, Ecuador 1, Egypt 1, England 1, Ethiopia 4, Kenya 2, Korea 2, Iran 3, Italy 1, Mali 1, Nepal 2, Pakistan 1, Philippines 1, Syria 2, Tajikistan 1, Thailand 1, Tunisia 1, USA 4, and Uruguay 2. Forty scholars studied wheat breeding and 30 studied rice breeding. Twenty seven scholars were ladies. Applications for the 7th round were due on or before February 1, 2015. A unique feature of the MBBIScholars Program is the requirement that scholars must complete part of their PhD program in both developed and developing/transition countries. Scholars have worked with developed country scientists as follows – Australia 4, Canada 3, USA 43, and Western Europe 20. The program pays for the MBBIScholars to participate in a 3 day Leadership course prior to attending the World Food Prize during their first 2 years. It has been a good experience to see MBBIScholars gain self-confidence after attending the Leadership Course and World Food Prize, and as they study and conduct research in developed and developing/transition countries. They also gain many lifelong contacts in the plant breeding community. Based on the current funding agreement with Monsanto, the final round of MBBIScholars will be selected from applications due February 1, 2016. In view of the great success of this model of training international plant breeders, it would be highly desirable for donors to support and extend this PhD training program to include additional crops of interest in developed and developing countries.
OR Melhoramento de Sementes Ltda., Brazil
Wheat is the best cropping option for the winter season in southern Brazil. According to current predictions the wheat area in 2015 will decline by 5.3% (146 thousand hectares) due to low prices for cereal grain and to high precipitation and disease severities (principally FHB and wheat blast) in 2014 that caused high losses in production. Due to high inoculum pressure leaf rust is controlled every year by resistance genes and fungicide application (an average three applications during the growing season to control all wheat diseases). Of 119 cultivars possibly cultivated in Brazil, 58 are moderately susceptible or susceptible to leaf rust. The objective of this study was to survey the Puccinia triticina population in order to identify the predominant races in Brazil. Infected leaves were collected from wheat crops in different regions in 2014. After isolating pustules and increasing the inoculum, the Thatcher differential lines [Lr1 2a 2c 3a (set 1), Lr9 16 24 26 (set 2), Lr3ka 11 17 30 (set 3), Lr10 18 21 23 (set 4), Lr14a 14b 10+26 20 (set 5), Lr3bg 27+31 and line ORL04002 - Toropi/Ônix) were inoculated. From 186 field samples, 74 isolates were evaluated. Race T(DF)T-MT, first identified in 2007, was predominant in 2013 and 2014. The frequency of race TDP-M(RT), first identified in 2008, increased to second position in 2014. Stripe rust and stem rust are not common diseases in Brazil; however, samples of both diseases were collected in 2013, but not in 2014. Most of the Brazilian OR Sementes lines evaluated in Argentina in 2014 stood out by resistance to stem rust, indicating the importance of incorporating resistance to all three rusts in Brazilian cultivars.
Indian Council of Agricultural Research
Leaf rust of wheat causes considerable losses worldwide. New pathotypes may cause previously resistant varieties to become susceptible. Identification of pathotypes and their relationships provide information for breeding efforts and designing management strategies. Traditional identification of pathotypes is based on responses of differential hosts. At present 50 pathotypes of P. triticina are maintained in the National collection. To determine variability and relationships at the molecular level we conducted analyses with 26 SSR primers, eight of which were polymorphic. Binary (0 or 1) molecular data generated by NTSYS-pc was used to construct a phylogenetic tree. Cluster analysis was done using the unweighted pair group arithmetic means (UPGMA) method in the SAHN program of NTSYS-pc. Pathotype groups and subgroups were determined based on the Jaccard similarity coefficients (JC). Manual observations indicated seven major groups. Among them, two groups each have one pathotype (pathotypes 16 and 17). Jaccard similarity coefficients supported groupings based on pathogenicity data. For example, pathotypes in the race 12 group (12, 12-1, 12-3, 12-4, 12-6, 12-7, 12-8, but excluding 12-2 and 12-5) had similarity coefficients greater than 0.7. Similar observations were recorded for the race 77 group. Maximum similarity was observed between 12-3 and 12-7 (JC value: 0.89) followed by 12-3, 12-7 and 12-6 (JC value: 0.82). Based on the phylogenetic tree and similarity coefficients data, there was substantial diversity among pathotypes. Thus SSR marker data can be used for effective characterization of pathotypes and for making evolutionary inferences.
National Institute of Agricultural Research (INIA), La Estanzuela Experimental Station, Uruguay
Breeding for durable leaf rust resistance is a priority for our breeding programs; however, the availability of new resistance genes is a limiting factor. Two spring wheat populations totaling 186 lines derived from three resistant donors and two Uruguayan susceptible cultivars were used to detect genomic regions associated with seedling and field resistance to LR in Uruguay. AUDPC were recorded in three environments in the 2012 and 2013 cropping seasons, and seedling responses were determined using three Puccinia triticina races. The lines were also genotyped using GBS. A total of 5,222 SNP markers were used for genome-wide association analysis. Molecular markers were used to genotype APR genes Lr34 and Lr68. We identified 43 SNP markers significantly associated with seedling resistance and 19 for field resistance on chromosomes 1A, 1B, 1D, 2B, 2D, 3A, 4A, 5B, 6B, 7A, 7B and 7D. We confirmed the presence of Lr10 and Lr16 in seedling tests and Lr34 and Lr68 in field tests. Novel genomic regions were identified on chromosomes 4A associated with APR, and 5B associated with seedling resistance. These new resistance genes will be useful in breeding for durable LR resistance.
Seed-Co Ltd., Rattray Arnold Research Station, Zimbabwe
Four Ug99 pathotypes occur in southern Africa. Although South African bread wheat cultivars and lines are regularly screened against representative isolates, the stem rust reactions of Zimbabwean germplasm to these variants were largely unknown. A collection of 49 wheat cultivars and lines, obtained from Seed-Co (Ltd.) and the Crop Breeding Institute in Zimbabwe, were tested as seedlings against pathotypes TTKSF, TTKSF+, TTKSP and PTKST. Twelve varieties and 21 experimental lines showed low infection types with all four pathotypes. Using molecular marker assays Sr31 was detected in 26 entries, Sr24 in five and Sr36 in one. The csSr2 marker suggested the presence of Sr2 in 20 entries. Screening of adult plants in the greenhouse using pathotype PTKST showed 34 entries with low infection types and 15 had high infection types. Stem rust field records in 2012 showed 5 susceptible entries with stem rust scores between 50S and 80S, whereas only 4 susceptible entries were identified in 2014 with scores ranging from 30S to 80S. Three lines were susceptible in both seasons. The study exposed the vulnerability of Zimbabwean wheat germplasm to Ug99 variants, but also identified suitable lines that can be used in breeding and possible commercialization.