Recurrent outbreaks of rusts debilitated mega wheat varieties in major production areas in Ethiopia. Projects to accelerate seed multiplication of rust resistant varieties funded by USAID, BMGF and others contributed to the replacement of the widely grown susceptible varieties Kubsa and Galama. In 2013/14, a new Pgt race (TKTTF) - unrelated to Ug99 - caused 100% yield losses on bread wheat variety Digalu. The continuing epidemic calls for fast replacement of the now susceptible varieties by accelerated seed multiplication to scale-up new varieties with durable rust resistance, and demonstrations to promote their adoption. In 2014, CIMMYT initiated a short term R4D project ‘Emergency Seed Support and Demonstration of Rust Resistant Wheat Varieties in Stem Rust Affected Areas of Ethiopia’. The project was financed by USAID and implemented in collaboration with EIAR, regional agricultural research institutes, and the Oromia Bureau of Agriculture. In collaboration with DRRW, CDL, and WSU, technical assistance was given to research centers to phenotype and genotype their breeding lines and commercial cultivars. A total of 352 Development Agents (15% female) were trained in rust identification, seed technology and crop management. Eight rust resistant varieties were demonstrated on 430 model farms in 16 districts in Oromia, Amhara and SNNPR. Awareness was created through field days organized by the Kulumsa and Sinana research centers in Arsi and Bale, respectively. Technical and financial support was given to four federal (Kulumsa, Werer, Debre Zeit, and Holetta) and three regional (Mekele, Sinana, and Adet) research centers for early generation seed multiplication. A total of 2,000 resource-poor farm households (10% female headed) selected on the basis of having suffered heavy losses to stem rust in the previous season, received technical assistance and 165 tonnes of seed of rust resistant varieties. Assisted farmers recorded above average zonal yields in 2014/15.
Primary Author: Badebo, CIMMYT-Ethiopia
Heat stress globally remains the most important factor determining yield anomalies. Terminal heat stress shortens the duration of grain filling. Hence, this investigation was undertaken during the cropping season 2016-17 to evaluate heat stress tolerance of 32 bread wheat genotypes planted in timely (optimal temperature) and late (terminal heat stress) sown condition at Agharkar Research Institute, Pune. Data were collected and analyzed for various agronomical and physiological traits and also selection indices for stress tolerance, derived from grain yield of wheat genotypes under optimal and late sowing conditions. It was observed that the genotypes DBW 187, GW 477, HD 2932, DBW 107, PBW 752 were the highest yielding under timely sown condition whereas, HD 3226, DBW 187, HP 1963, HD 3219, DBW 196 were the highest yielding under late sown condition. DBW 187 was found to withstand the stress conditions. Minimum percent yield decrease and high yield stability index (YSI) was found in HD 3219 followed by HD 3226 and DBW 196 which indicated their better performance under stress condition. Harmonic mean, a stress tolerance selection index was found to be the best fit of linear model (R2 = 0.78) and a good indicator of high yield under heat stress condition. Physiological parameters, Chlorophyll (SPAD), canopy temperature (Infra-red thermometer) and vegetation index (NDVI) have not shown significant relation with yield, however, they were found to be significantly associated with yield contributing traits like biomass, thousand grain weight, grain number per spike. DBW 187 and HP 1963 showed stable yields with high PCA 1 and low PCA 2, indicating their resilience to stress conditions. The investigation has resulted in identification of genotypes for terminal heat stress conditions and also given greater insights in understanding the importance of physiological traits and stress tolerance indices in selection process.
Primary Author: Bagwan, Agharkar Research Institute Pune
Disease surveillance is very important in establishing the status of disease response in crops. During the 2014 to 2016 wheat seasons, foliar blight (spot blotch caused by Bipolaris sorokiniana and tan spot caused by Pyrenophora tritici-repentis) was recorded as severe across the entire whole plains region. Foliar blight was moderate in the mid hills, especially the Kathmandu valley. Leaf rust was severe (10MS - 100S) at several places in the mid hills. This could be due either to climatic conditions or varieties susceptible to the prevailing pathotypes. Yellow rust was also recorded up to 100S in the Kathmandu valley. Newly released varieties Gaura and Dhaulagiri showed yellow rust incidence of 20MS to 40S. Stem rust was sporadic and light and was observed very late in the season (tR - 10MR) in far western districts and the Kathmandu valley. Powdery mildew was moderate and localized. Loose smut was found at low levels throughout the mid hills. In 2014, Karnal bunt (caused by Tilletia indica) was also recorded in far western regions. Five different pathotypes of P. triticina (121R63-1, 21R55, 21R63 and 0R9) and one Pst pathotype (110S119) have prevailed during the last few years. Wheat genotypes were evaluated at Khumaltar and those reputed to have Yr27, Yr27+, Yr27+Yr18, Yr31+APR, Yr9, Yr10 and Yr15 were resistant. Similarly, genotypes containing Lr34+ had lower leaf rust severities than others.
Primary Author: Baidya, Plant Pathology Division, Nepal Agricultural Research Council
Dr. Norman Borlaug stated that rust never sleeps and this enables rust pathogens to produce new strains capable of putting rust resistance genes to rest. These pathogens continue to pose threats to global wheat production. Wheat breeders have made significant progress to control rust outbreaks using conventional selection technologies; however, some critical shifts in pathogen populations have let them down. Rapid evolution in molecular marker technologies in the last 15 years and refinement of phenomic facilities have expedited the process of discovery and characterisation of rust resistance genes to underpin the development and validation of markers closely linked with genetically diverse sources of resistance. A high proportion of the formally named rust resistance genes were characterized in the 21st century and markers closely linked with these genes have been developed and validated. The marker tagged sources of resistance to three rust diseases have equipped the wheat breeding community with tools to deploy combinations of all stage and adult plant resistance genes in future wheat cultivars. The question that whether we have enough resistance genes discovered to compete against the ever-awake rust pathogens. In our opinion, we cannot be complacent and discovery needs to continue to ensure food security. This presentation will discuss the role of advances in phenomic and genomic technologies to achieve durable rust control in wheat.
Primary Author: Bansal, University of Sydney Plant Breeding Institute
Wheat stem rust (SR), caused by Puccinia graminis f. sp. tritici, (Pgt) is considered one of the most destructive diseases of the wheat crop. As Sr24 and Sr31 are the most widely used resistance genes in the Southern Cone of America, wheat crops in this region is under threat of SR outbreaks posed by the potential migration of virulent Pgt Ug99-lineage races (Ug99+). Efforts have to be made to develop adapted lines resistant to Ug99+. Genes Sr26, Sr32 and Sr39 are effective to both Ug99+ and local races of the pathogen. This work is aimed to pyramid two and three of the resistance genes in two locally adapted wheat cultivars (G?nesis 2375 and G?nesis 6.87). Donor lines of Sr26, Sr32 and Sr39 (developed by I. Dundas, University of Adelaide, Australia) and molecular markers Sr26#43, csSr32#1 and Sr39#22r (developed by R. Mago et al., University of Adelaide) were used. Lines with two-gene combinations were developed in two steps. First, tree-way crosses were made by crossing heterozygous F1 plants (derived from crossings donor lines) to either one of the two adapted wheat cultivars. Subsequently, tree-way F1 plants were genotyped and only those with two-gene combinations were backcrossed (BC) twice to the adapted cultivars. Among three-way F1 plants, two-genes combinations were confirmed for Sr26+Sr32 (8 out of 31), Sr26+Sr39 (2 of 115) and Sr32+Sr39 (26 out of 103). In the BC1F1 generation, Sr26+Sr32, Sr26+Sr39 and Sr32+Sr39 combinations corresponded with 9, 9 and 45 out of 99, 27 and 241 plants, respectively. In 2017, 1345 BC2F1 plants are being grown to obtain BC2F2. We plan to intercross plants with two-gene combinations to obtain lines with the three genes which will be used as sources of resistance to develop cultivars with presumably longer lasting resistance to wheat SR.
Primary Author: Baraibar, Instituto Nacional de Investigaci?n Agropecuaria (INIA) La Estanzuela
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.
Primary Author: Barcellos, OR Melhoramento de Sementes Ltda., Brazil
The major diseases of wheat in Bangladesh are leaf blight and leaf rust. Yellow rust occurs occasionally with sporadic infection in the northern parts whereas stem rust was observed only in 2014. So far the country is free of Pgt race Ug99. Wheat blast, a devastating head disease, was first reported in 2016. Currently, about 65% of the wheat area in Bangladesh is covered by leaf rust resistant varieties and about 30% of the area is covered by Ug99 resistant varieties. Surveillance and monitoring of diseases is conducted regularly. In 2017, 102 sites were surveyed of which 52% had leaf rust infection. The data were uploaded to the Wheat Rust Tool Box. A separate surveillance and monitoring of wheat blast was conducted on 421 farmers? fields in 24 districts. Different levels of blast incidence were recorded in 77 fields. The Wheat Research Centre in Bangladesh works with CIMMYT and BGRI to develop high yielding rust resistant varieties. This includes screening for response to Ug99 at KALRO, Kenya. However, the current major concern of wheat is wheat blast. The popular variety BARI Gom 26 is highly susceptible to this disease and no current cultivar in Bangladesh carries an acceptable level of resistance to blast. During 2016-17, 20 varieties and advanced lines from Bangladesh and 80 from CIMMYT Mexico, were evaluated. One elite breeding line, BAW 1260, showed resistance (<10% severity) in multiple environment tests and is also resistant to leaf blight and stem rust. This line carries the 2NS translocation from Aegilops ventricosa and will be released soon for commercial cultivation. Pre-release seed multiplication is already underway for rapid dissemination. Among recently released wheat varieties BARI Gom 30 and BARI Gom 32 are moderately tolerant to blast and are being promoted for wider adoption by farmers.
Primary Author: Barma, Bangladesh Agricultural Research Institute
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.
Primary Author: Barma, Bangladesh Agricultural Research Institute (BARI)
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.
Primary Author: Barnes, Universidad de las Américas, Ecuador
In the northeastern United States, outside the boundaries of the 20th century federal barberry eradication zone, both common barberry (Berberis vulgaris) and Japanese barberry (B. thunbergii) are found in great abundance, to the extent that both are considered invasive species. Much less common and relatively less studied is their interspecific hybrid, B. ×ottawensis, which has been produced in the ornamental horticultural industry but which also occurs naturally. Since B. vulgaris is a competent host of Puccinia graminis and B. thunbergii is not, B. ×ottawensis presents a unique system for characterizing the genetic mechanism(s) underlying what appears to be non-host resistance to P. graminis in B. thunbergii. In this study, a natural population of about 1,000 individuals (mixed B. vulgaris, B. thunbergii, and B. ×ottawensis) in Sheffield, MA, was investigated. While wide morphological variation was observed among and within the populations of all three species at the site, the most pronounced variation was observed among B. ×ottawensis individuals. A subset of the population was selected for genotyping by sequencing (GBS) and evaluated for reaction to P. graminis via controlled inoculations. The response was found to segregate clearly among B. ×ottawensis individuals; and GBS was shown to be a viable means of generating molecular markers in these species, despite the lack of a reference genome. These results suggest that P. graminis resistance in B. thunbergii can be genetically mapped, and mapping populations are currently under development to accomplish this goal. The genomic resources developed in this work may facilitate both barberry surveillance efforts and ornamental barberry testing programs. Furthermore, knowledge of the genetics of response to P. graminis in the alternate host has the potential to inform efforts in breeding for stem rust resistance in wheat.
Primary Author: Bartaula, Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, USA