Location: Sugarbeet and Bean ResearchTitle: Seedling diseases of sugar beet – diversity and host interactions Author
Submitted to: Annual Beet Sugar Development Foundation Research Report
Publication Type: Research Notes
Publication Acceptance Date: 4/15/2015
Publication Date: 6/1/2015
Citation: Hanson, L.E., McGrath, J.M., Goodwill, T.R. 2015. Seedling diseases of sugar beet – diversity and host interactions. [CD-ROM] 2014 Annual Beet Sugar Development Foundation Research Report. Denver, Colorado: Beet Sugar Development Foundation.
Technical Abstract: Seedling diseases cause loss of plant stand due to pre- and post-emergence damping-off and weakened plants due to root or hypocotyl infection. Several pathogens cause seedling disease of sugar beet, including Rhizoctonia solani, Aphanomyces cochlioides, Pythium species, and Fusarium species. Different anastomosis groups (AG) of R. solani can cause seedling damping-off in beet, with AG-4 and AG-2-2 commonly reported, although other AG may cause damage. Isolates from sugarbeet seedlings showing damping-off symptoms with a high proportion of Fusarium spp. at 100% of fields sampled in 2014. With the wet spring, Aphanomyces and Pythium were isolated from approximately 60% of samples collected. Rhizoctonia solani was less common than in prior years, being isolated from 35% of the samples. R. solani, Fusarium spp, and Aphanomyces all were isolated as the sole organism cultured from at least one plated beet plant while Pythium was isolated only from beets that also yielded one or more other potential pathogens. Phoma was isolated from two of the samples at one seedling each from two different fields. Isolates of all of these genera caused damping-off symptoms when inoculated onto sugarbeet germplasm USH20. For Rhizoctonia solani, evidence from 2014 tests continue to show differential susceptibility for the AG tested. All materials screened to date with seedling resistance also have some level of resistance to Rhizoctonia crown and root rot as adult plants. Recombinant inbred lines from a cross between a Rhizoctonia-resistant and a Rhizoctonia susceptible parent showed a wide range of responses, indicating the utility of this material for future studies on the interaction between R. solani and sugar beet.