The North-Central region is the top producer of oats in the United States. However, oat production in this region is constrained by crown rust disease caused by the fungus Puccinia coronata, the most devastating disease of oat worldwide. Epidemics in the recent years have caused production losses of up to 50%. This project aims to minimize these losses by developing new oat germplasm that are resistant to crown rust. As an initial step, crosses of resistant wild relative and susceptible cultivated parents were made to develop eight mapping populations to guide genetic mapping efforts. These populations will be evaluated in field plots for resistance, and SNP markers will be developed to map the locations of genes or loci contributing to this trait. Once candidate genes are identified from different populations, multiple parents will be crossed to pyramid these genes. When advanced, the pyramided lines and associated linked markers will be forwarded to breeders for inclusion in their oat varietal improvement programs. Learning outcomes include knowledge enhancement about sources of resistance and plant immune mechanisms accessible to plant pathologists and breeders. The evaluation plan for these outcomes will be based on the number of seminars or presentations given and number of reads/downloads and citations of published papers. Action outcomes will be the use of this project’s germplasm by breeders to develop new oat varieties and adoption of developed methodologies by members of our scientific community (plant geneticists and molecular biologists). The evaluation plan for the action outcomes will be the actual use of our germplasm in oat breeding programs, and number of reads/downloads and citations of published papers. The long term goal of this project is to increase the overall income of oat growers and boost the production of healthy oat with use of enhanced crown rust resistant varieties.
The learning outcomes from this project include: 1) development of new sources of multi-gene resistance for oat varietal improvement; and 2) information about these new resistance genes/QTLs and their inheritance pattern, all available to the scientific community for utilization and crop improvement. The target audience for this project is primarily the oat scientific community. This work aims to generate scientific results useful and valuable for the oat industry, particularly in the NCR. Findings from this project also can benefit production in other grains as adult plant resistance can be broad spectrum and the orthology among genes in cereals may allow crop translational applications.
The action outcomes include the use of germplasm generated from this project to breed new oat cultivars; adoption of methods and use of generated data to identify new sources of resistance and better understand the molecular genetic basis of adult plant resistance. Historically, oat cultivars only last a maximum of five years in the field before their resistance to crown rust is broken. The pathogen evolves rapidly and acquires new virulence traits over time. Therefore, there is a constant need to develop new varieties to avoid epidemics and severe economic losses. This project addresses the pre-breeding bottleneck, which is finding novel sources of resistance genes that are easy to cross with the existing cultivars. Ultimately, this project leads to more durable crown rust- resistant cultivars that growers can adopt, which would then help maintain the status of NCR as the top oat producer in the US.
The aim of this project is to identify and pyramid new resistance genes to manage oat crown rust, a prevalent disease in the North Central Region. In 2018, I have screened five mapping populations (OtanaA x CI7035-1, OtanaA x CI8000-4, OtanaA x PI266887-1, OtanaD x PI260616-1, and OtanaI x PI263412-1) in the Buckthorn Nursery in St. Paul, MN to evaluate the oat lines for crown rust resistance. Based on the segregation data on resistance, oat lines from two populations (OtanaA x CI8000-4 and OtanaD x PI260616-1), were selected for subjection to a molecular technique called Oat SNP Chip genotyping in the USDA Genotyping Lab in Fargo, ND to associate the resistance phenotype to regions (loci) of the oat genome. These regions potentially contain new resistance alleles that can be used for oat breeding for crown rust resistance. I also developed genetic markers for these loci for marker-assisted selection and determined the proportion of the phenotype explained by the markers. Further, I have started oat crosses to combine this locus with other previously identified loci so that I can pyramid them into a single line and release it later as a breeding germplasm. To our knowledge, this is the first attempt to combine adult plant resistance genes for rust in oats. I have presented a poster of these results at the International Congress of Plant Pathology Meeting in Boston, MA in August 2018 (see attached poster) and gained experience on communicating my research to an international audience. Nazareno_ICPP2018_Poster_v3
In my analysis, I found one major region in oat linkage group 21 (Mrg21) that controls resistance in the two mapping populations that were sent for genotyping. This is in addition to what USDA Cereal Disease Laboratory researchers have identified previously. I have developed markers for this locus and found that the effect of this region on crown rust resistance range from 31-50%, which is quite significant. To combine this locus with the other loci, I have initiated oat crosses with nine parents in Spring 2018 and so far, the markers that I have developed were able to differentiate resistant and susceptible oat genotypes. This will be of great help in further selection in the later generations. Currently, I have F2 and F3 progenies from my crosses and some of them are already fixed for the resistance locus. There is currently no single resistance gene that can withstand all races of crown rust in the field, so quantitative resistance, as the one that this project is exploiting is viewed to be the best way to achieve durable crown rust resistance. Compared to chemical control, genetic resistance is less costly and deemed to be more sustainable.
The beneficiary for this project is primarily the oat scientific community and later, the growers, when the oat germplasm is released. Presenting these results in an international meeting is therefore a great outcome for this project, which enabled sharing of the research outputs to scientists around the world. In the meeting, I have interacted with several scientists, researchers, and students from all over the world and talked about my research. I thought it was a great avenue to learn and share experiences with other people in your field. In addition, some people also visited my research plots in the Buckthorn Nursery in the University of Minnesota St. Paul Campus. These include research personnel from the College of Food and Natural Sciences, UMN and a scientist from the Grains Research and Development Corporation, Australia. I had the chance to explain my research while showing my rusted and resistant plants in the field.
Educational & Outreach Activities
Other than participation in an international meeting and showing my plots to some visitors, I don’t have anything more to report on education and outreach.
Our primary output from this project would be the breeding germplasm that we will release to oat breeders as donor for crown rust resistance. Breeders can then use the germplasm for cultivar development, which would eventually be released and planted by growers as cultivars. Therefore, this project basically deals with pre-breeding oat for crown rust resistance. Though it does not have a direct benefit to growers right now, resistant cultivars developed from this project’s germplasm will certainly help growers cope up with crown rust in the future.
Oat production has decreased in the US in the past decades and crown rust contributed to the decline somehow. Because of crown rust and other factors (i.e. low profitability), growers are hesitant to plant oats and would rather plant corn or soybean. Since oat is considered as a “health” crop, fungicide spraying is not encouraged, particularly for organically-grown oats. This project aims to address that problem so that growers of oat, organic or not, would not take a lot of losses due to crown rust like the one that happened in Minnesota and South Dakota in 2014 when both states lost 50% and 35% of the yield, respectively, due to crown rust.
Our project aims to develop a sustainable way to manage crown rust and we still think that breeding for disease resistance by combining multiple resistance genes would be the best approach to combat this disease. The more new genes that we discover from resistant donors, the more we realize that there is still genetic diversity in oat that remains to be explored. We plan to exploit these untapped resources and use them for our own advantage to develop lines that are resilient to crown rust. We also realize that the pathogen is always changing, almost every year, as new races are being produced after completing its life cycle in buckthorn (alternate host). This always reminds us not to be complacent and to be careful in deploying resistance genes out in the field in the future.