Location: Soil Management and Sugarbeet Research
2020 Annual Report
Objectives
Objective 1: Identify novel resistance genes to major sugar beet fungal pathogens and sugar beet cyst nemotode within sugar beet genetic resources, especially its crop wild relatives; introgress the discovered novel sources of resistance into sugar beet germplasm for release; incorporate evaluation and characterization data into the Germplasm Resources Information Network (GRIN) database; and screen sugar beet germplasm and commercial lines for major fungal pathogens.
Sub-objective 1A: Introgress novel sources of resistance to major pathogens into sugar enhanced beet germplasm for release.
Sub-objective 1B: Screen 64 selected accessions of Beta vulgaris subspecies maritima (B.v. subsp. maritima) using single nucleotide polymorphic (SNP) markers linked to resistance genes. Confirm the resistance to these important diseases and begin to introgress novel sources of resistance into sugar beet germplasm for release.
Objective 2: Identify and characterize genetic interactions, biochemical pathways, and metabolic processes that control interactions between sugar beet and fungal pathogens, for more efficacious disease resistance selection and improved germplasm for breeding programs, and to provide practical disease management recommendations for sugar beet producers.
Sub-objective 2.A: Screen sugar beet germplasm with the newly discovered pathogen, Fusarium secorum, to identify resistance to the disease caused by this pathogens, Fusarium yellow decline, and to compare resistance in these sugar beet populations to the more traditional disease, Fusarium yellows primarily caused by Fusarium oxysporum f. sp. betae. (Webb)
Sub-objective 2.B: Using metabolomic profiling, characterize the biological pathways that are induced during susceptible and resistant interactions with F. oxysporum f. sp. betae and F. secorum.
Approach
The sugar beet research within the Soil Management and Sugar Beet Research Unit contributes to the broader, national sugar beet research effort by USDA-ARS. Our research focuses on sugar beet disease because they remain an important source of pre- and post-harvest crop and sugar losses throughout the United States and internationally. Although advances have been made effective tools for managing important diseases are lacking. The pathogenic fungi Rhizoctonia and Fusarium and the sugar beet cyst nematode have particular economic importance because they are among the major limiting factors for sugar beet production nationwide. As part of a national sugar beet improvement program, we will apply a focused approach to enhance crop improvement methods and produce resistant germplasm through increased understanding of sugar beet genetics, some of its major pathogens, and its wild relatives. This project will exploit increased understanding of sugar beet/pathogen interactions and improve the understanding of pathogen diversity. We will use this knowledge to more quickly and cost effectively select disease resistant germplasm and develop superior disease management strategies. The breeding and pathology components of the project are focused on enhanced sugar beet germplasm through increased understanding of important sugar beet diseases and their epidemiology. This is especially crucial in diseases for which there is no chemical protection or where crop protectants are being phased out.
Progress Report
ARS researchers have made significant progress in the past year in transitioning the approaches used to characterize and improve sugar beet germplasm towards genome-guided approaches, while continuing to execute large scale phenotypic screens of germplasm for the major sugar beet diseases. We have also made progress on characterizing the interaction of multiple Fusarium spp. (F. oxysporum f. sp. betae, F. commune, and F. secorum) with sugar beet and characterizing the defense response for two sugar beet diseases, Fusarium yellows and Fusarium yellowing decline.
On Objective 1, we have spearheaded a new national effort to sequence the genomes of the most utilized ARS germplasm releases to associate genomic signatures with disease resistance phenotypes. This work complements other related ARS research projects to use genomics to characterize unimproved wild germplasm, including Beta vulgaris subspecies maritima and Patellifolia species. In the past year, we have begun working through the backlog of unreleased improved germplasm from the Fort Collins, Colorado, and Salinas, California, breeding programs to prepare these germplasms for release to key sugar beet industry stakeholders. Release will occur after confirming resistance for select diseases. We have completed the genotyping of the panel of 64 Beta vulgaris subspecies maritima accessions using single nucleotide polymorphic (SNP) markers linked to resistance genes for sugar beet cyst nematode and rhizomania and confirmed the resistance phenotypes linked to these traits.
On Objective 2, progress has been made to screen germplasm for resistance to the novel sugar beet disease, Fusarium yellowing decline and compare to resistance to the more common Fusarium yellows (Sub-objective 2.A). In fiscal year 2019 we discovered that some isolates previously described as F. oxysporum f. sp. betae were actually the novel pathogen F. secorum and that previous disease reports may have been causing Fusarium yellowing decline and not Fusarium yellows. Two of three replications for screening 33 putative resistant lines with 9 Fusarium spp. isolates have been completed with the final replication ongoing. We have begun experimental treatments for characterizing the metabolome of sugar beet during infection with F. commune and F. secorum (with two of three replications already completed; Sub-objective 2. B).
Accomplishments
1. Completed national-level screening of sugar beet germplasm and ARS releases for resistance to major sugar beet pathogens. USDA-ARS sugar beet breeding programs have developed many unique disease resistance traits, and ARS germplasm is used globally by the sugar beet industry. In a long-term effort, ARS scientists in Fort Collins, Colorado, cooperating with other ARS scientists and industry breeders evaluated thousands of sugar beet accessions in the USDA National Plant Germplasm System (NPGS) for resistance to a wide array of destructive diseases. Germplasm identified in this coordinated systematic screening are the basis for improving germplasm releases containing critically needed new sources of host plant resistance to beet curly top, rhizomania, and rhizoctonia crown and root rot. The disease resistant genes expressed by the various cultivars now allow sugar beet breeders to select superior germplasm for incorporation into disease resistance breeding programs. Through these disease nursery screenings, USDA-ARS provides a unique, global resource by identifying public germplasm with new forms of host plant resistance to support the resiliency of American beet sugar production.
Review Publications
Chopra, R., Johnson, E., Emenecker, R., Cahoon, E., Lyons, J., Kliebenstein, D., Daniels, E., Dorn, K.M., Esfahanian, M., Folstad, N., Frels, K., McGinn, M., Ott, M., Gallaher, C., Altendorf, K., Berroyer, A., Ismail, B., Anderson, J., Wyse, D., Umaslov, T., Sedbrook, J., Marks, D.M. 2020. A large-scale multi-faceted screen identifies crucial domestication traits needed to create a new ecofriendly cash cover crop. Nature Food. https://doi.org//10.1038/s43016-019-0007-z.
Strausbaugh, C.A., Dorn, K.M., Fenwick, A.L. 2020. Beet curly top resistance in USDA-ARS Ft. Collins germplasm, 2019. Plant Disease Management Reports. 14:CF043.
Boundy-Mills, K., McCluskey, K., Elia, P., Glaeser, J.A., Lindner, D.L., Nobles, Jr., D.R., Normanly, J., Ochoa-Corona, F.M., Scott, J.A., Ward, T.J., Webb, K.M., Webster, K., Wertz, J.E. 2020. Preserving US microbe collections sparks future discoveries. Journal of Applied Microbiology. 129(2):162-174. https://doi.org/10.1111/jam.14525.
