Location: Sugarbeet and Bean Research
2020 Annual Report
Accomplishments
1. Genetics of Rhizoctonia resistance genes in beet. Rhizoctonia root and crown rot (RRCR) is the most important soil-borne disease of sugar beet in the world. ARS scientists have a long history of breeding for resistance, but the mechanism is not understood, but we know multiple genes are involved. Better knowledge of the resistance mechanism could speed up plant screening and getting resistance into varieties with other desired characters for stakeholders. In collaboration with ARS researchers from Beltsville, Maryland, ARS researchers in East Lansing, Michigan, identified possible resistance genes for RRCR in sugar beet, particularly polygalacturonase inhibitor protein genes (PGIPs). Polygalacturonases are proteins that break down the plant cell wall, especially pectins. When a common model plant, Nicotiana benthemiana (N. benthemiana), a relative of tobacco, was transformed with these genes, the plants showed reduced damage with a single isolate for the causal agent of RRCR, Rhizoctonia solani (R. solani). This model plant was tested with a range of fungal isolates because tests with host plants such as dry bean and beet have shown varied resistance responses to different strains, so screening was done to determine how widespread the interaction might be. Strains that varied in their effect on the N. benthemiana were used for sequencing, and candidate pectin-degrading genes (PGs) identified. Three R. solani strain types varied in PGs, with more found in the type that is most damaging to beet. Variable response was observed depending on the PGs in the fungus and the PGIPs in the host, similar to what has been observed in the dry bean system. Understanding this interaction may allow for targeted selection of resistance depending on the major pathogen type in the growing area. These results could help breeders develop resistant varieties and give new options for disease management to growers.
Review Publications
Pethybridge, S.J., Sharma, S., Hansen, Z., Kikkert, J.R., Olmstead, D.L., Hanson, L.E. 2020. Optimizing Cercospora leaf spot control in table beet using action thresholds and disease forecasting. Plant Disease. 104:1831-1840. https://doi.org/10.1094/PDIS-02-20-0246-RE.
Galewski, P.J., McGrath, J.M. 2020. Genetic diversity among cultivated beets (Beta vulgaris) assessed via population-based whole genome sequences. BMC Genomics. 21:189. https://doi.org/10.1186/s12864-020-6451-1.
Pethybridge, S.J., Sharma, S., Hanson, Z., Vaghefi, N., Hanson, L.E., Kikkert, J.R. 2019. Improving the fungicide-based management of Cercospora leaf spot in table beet in New York. Canadian Journal of Plant Pathology. https://doi.org/10.1080/07060661.2019.1690048.
Kunert, A.T., Pohlker, M.L., Krevert, C.S., Wieder, C., Speth, K.R., Hanson, L.E., Morris, C., Schmale, D.G., Poschl, U., Frohlich-Nowoisky, J. 2019. Macromolecular fungal ice nuclei in Fusarium: effects of physical and chemical processing. Biogeosciences. 16:4647–4659. https://doi.org/10.5194/bg-16-4647-2019.
Rosenzweig, N., Hanson, L.E., Jiang, Q., Mambetova, S., Guza, C., Stewart, J., Somohano, P. 2020. Temporal population monitoring of fungicide sensitivity in Cercospora beticola from sugarbeet (Beta vulgaris) in the Upper Great Lakes. Canadian Journal of Plant Pathology. https://doi.org/10.1080/07060661.2019.1705914.