Department of Plant Pathology, University of Minnesota, USA
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Berberis holstii, native to the highlands of East Africa, is susceptible to Puccinia graminis and P. striiformis in artificial inoculations. However, it is not known whether these pathogens complete their sexual cycles in the region. In an attempt to understand the role of B. holstii in pathogen variation and epidemiology of wheat stem rust and stripe rust, we investigated the functionality of B. holstii as an alternate host. Natural aecial infections on B. holstii were observed and sampled in August at Mt. Kenya and Narok (Kenya), and June to December at North Shewa (Ethiopia) from 2008. Aeciospores from the collections were inoculated to a panel of cereal species, including Line E and ‘Morocco’ wheat, 'Hiproly’ barley, 'Prolific' rye, and ‘Marvelous’ oat. For the majority of aecial samples, aeciospore viability was lost during shipment and storage; thus inoculations were not successful. Inoculations using relatively fresh samples collected at North Shewa in 2012 and 2014, resulted in stem rust infections on Line E, Prolific, Hiproly, and Marvelous. DNA assays using real-time PCR confirmed the presence of P. graminis in these samples. While it is likely that the pathogen infecting Line E, Prolific and Hiproly is P. graminis f. sp. secalis (Pgs), the inoculation and DNA assays did not provide sufficient resolution to distinguish Pgs from Pgt. Stem rust infections on Marvelous were assumed to involve Pg f. sp. avenae. Experiments are in progress to characterize isolates derived from these samples, and to determine if other rust fungi are present in these samples. Based on these preliminary data, we conclude that P. graminis completes its sexual cycle in Ethiopia. The contribution of the sexual cycle to the observed variation within the Pgt population in the region remains unclear.
CSIRO Agriculture Flagship, Australia
The Lr34 resistance gene from Triticum aestivum encodes a putative ABC transporter protein that confers broad spectrum, partial adult plant resistance to all three rusts species and powdery mildew. It has remained a durable source of resistance for over 100 years in which time no increased virulence towards Lr34 has been observed. This gene is located on chromosome 7D and consequently cannot be readily transferred to durum wheat by traditional breeding. A transgenic approach was used to transfer Lr34 to durum wheat cultivar Stewart by Agrobacterium transformation. Homozygous progeny from a number of independent Stewart lines expressing Lr34 under regulatory control of its endogenous promoter showed high levels of rust resistance at the seedling stage. A correlation between seedling resistance and transgene expression levels was observed in these plants. In contrast seedlings from a near isogenic line of hexaploid wheat cultivar Thatcher containing Lr34 showed only a minor difference in rust growth when compared with Thatcher seedlings, typical of this adult plant resistance gene in hexaploid wheat. Little is known about how the Lr34 gene product functions; however, the seedling resistance of these durum transgenics enables functional assays to be readily undertaken without the need for adult plant material. By infecting seedlings we have shown that day length has an effect on Lr34 resistance to leaf rust, with higher levels of resistance observed under long days (16 h light) compared with short days (8 h light). This study demonstrates that Lr34 provides strong and presumably durable seedling resistance to rust in durum plants that can be used to further understand how this gene confers resistance.
Bangladesh Agricultural Research Institute (BARI)
Leaf rust is most common wheat rust in Bangladesh. Late planted wheat crops are more likely to be affected. Yellow rust occurs occasionally with sporadic infection in the northern parts and stem rust was observed after three decades in 2014, but Ug99 races were not detected. The Wheat Research Centre in Bangladesh works in collaboration with CIMMYT and BGRI to develop high yielding rust resistant wheat varieties. Advanced lines and breeding materials are screened every year at KARLO, Kenya, and EARI, Ethiopia, for resistance to Ug99. Rapid multiplication of pre-released and newly released rust resistant varieties is given top priority for quick replacement of rust susceptible varieties. Currently, about 60% of the wheat area is covered by leaf rust resistant varieties released in the last five years, including around 20% of the area covered by varieties with adult plant resistance to Pgt race Ug99. About 40% of the wheat area is still covered by older varieties such as Prodip. Another Ug99 resistant variety (BARI Gom 29) released in 2014 is undergoing seed multiplication. Large scale seed multiplication of Ug99 resistant varieties is part of a broader strategy to mitigate the potential threat. In the last four years, about 125 tonnes of breeder seed and more than 50 thousand tonnes of certified seed of rust resistant varieties were produced and distributed to seed production agencies and to farmers. Rust surveillance is conducted on a regular basis in the major wheat growing areas. About 50% of the sites surveyed in 2014 had moderate to high severities of leaf rust, but in 2015 severities were much lower. These efforts have been very useful for sustaining and enhancing wheat productivity and production in Bangladesh.
Ethiopian Institute of Agricultural Research (EIAR)
Wheat rusts can be controlled by host resistance or chemicals. Ethiopian farmers are not widely experienced with chemicals. Sixty seven (49 bread wheat (BW) and 18 durum (DW)) non-replicated varieties were planted on 0.4 m2 plots at 22 rust hotspot locations in 2014. Kubsa and Digalu were used as susceptible checks for YR and SR, respectively. Rust severities were scored according to the modified Cobb scale. Ten YR and 12 SR hotspot locations with mean rust severities of ≥40% were used in data analyses. Kubsa had a mean 59% YR severity and Digalu, a 73% SR severity. Rust severity levels were divided into three categories, viz. low (≤35%), moderate (36-40%) and high (>40%), across locations for both diseases. The frequency of varieties with low YR severities in the BW group was 26.5%, medium 18.4% and high 55.1% compared to DW varieties at 61%, 28% and 11%, respectively. In the case of SR, both BW and DW had large proportions of entries in the high severity category at 69.4% and 72.2%, respectively. The medium and low SR severity groups were represented by 20.4% and 10.2% for BW, and 11.1% and 16.7% for DW, respectively. In summary, the top 10 widely cultivated BW and a few DW varieties categorised in the medium and high severity groups for both YR and SR, would definitely require fungicides in rust-prone areas for optimum disease control. Many cultivars released after 1974 are still cultivated indicating that susceptible varieties are only slowly replaced. Hence, development and distribution of resistant cultivars, replacement of susceptible cultivars, and training industry workers and farmers on effective field scouting and fungicide use will be paramount for sustainable wheat production in Ethiopia.
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
The durability of stem rust resistance in wheat varieties is strengthened by the use of polygenic, and broad-spectrum sources of resistance. Adult plant resistance (APR) was observed in the mid-20th century Ecuadorian bread wheat cv. Morocho Blanco (PI 286545) in field tests at Njoro, Kenya, and at St. Paul. Morocho Blanco was susceptible to races TTKSK, RCRSC and TPMKC at the seedling stage. A doubled haploid (DH) mapping population was created from a cross between Morocho Blanco and the susceptible line LMPG-6 to identify loci associated with APR phenotypes. Eighty-eight DH lines were genotyped with approximately 90,000 SNPs using a custom Infinium assay from Illumina. Sixty-seven additional DH lines were used to verify SNPs associated with reduced stem rust levels. Severity and infection type were assessed on adult plants at the stem rust screening facility in Kenya in 2013 and 2014, and in two single race nurseries inoculated with races RCRSC and TPMKC at St. Paul in 2014. Two identified and verified QTL reducing stem rust severity were located on chromosome arms 2BS and 6AS. The QTL on 6AS also reduced infection type at Njoro, but a similar reduction was not observed at St. Paul suggesting a genotype x environment or genotype x race interaction. The QTL on 2BS was associated with reduced stem rust severity at both Njoro and St. Paul. It is a strong candidate for use in breeding for APR to stem rust.
Universidad de las Américas, Ecuador
Identifying and tracking new races of wheat rust pathogens in a timely manner is important for early warning of disease potential in wheat-growing regions. Ecuador, located in northwestern South America, serves as a strategic monitoring location for rust fungi between the wheat production areas of North and South America. New races are likely to occur more often when the fungus is in the proximity of the alternate Berberis species host. More than 30 Berberis species have been reported in Ecuador, most of them endemic. However, most herbarium collections correspond to types, have only been found once, and/or date back 20 years or more. Therefore, the current status of diversity in Berberis spp. in Ecuador is largely unknown. Our goal is to collect Berberis species in Ecuador, document their distribution, prepare herbarium specimens, and identify the species morphologically and genetically. We will use this information to establish the relationships of neotropical Berberis species with Berberis in other parts of the world, and determine the pathogenicities of various rust fungi associated with them. Preliminary results show that the Ecuadorian Berberis spp. are phylogenetically distinct from those of Argentina and Brazil. To date, the rust fungi on Ecuadorean Berberis do not infect wheat. We have identified three potentially new rust fungal species based on DNA analysis.
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.