Submitted to: Journal of Sugarbeet Research
Publication Type: Abstract Only
Publication Acceptance Date: January 11, 1999
Publication Date: N/A
Technical Abstract: Evaluation of sugarbeet for resistance to Rhizoctonia root rot using field nurseries can be costly and subject to environmental variables that restrict disease development. A rapid method for the detection of resistance to Rhizoctonia root rot in sugarbeet in the greenhouse was developed. Sterile barley grain inoculated with an isolate of Rhizoctonia solani AG2-2 (R9 isolate) known to cause root rot in sugarbeet is the basic inoculum. Infested grain is used to inoculate 5 week-old sugarbeet plants in the greenhouse and evaluation of root rot severity is determined at 2-3 weeks post inoculation. Sugarbeet germplasm for the USDA Fort Collins breeding program and one commercial hybrid were used to validate the method and included highly resistant material (FC709-2 and FC718) and highly susceptible material (FC403 and Maribo "Ultramono"). Ranking of the germplasm accessions for percent healthy roots after inoculation in the greenhouse was similar to the ranking of the same germplasm in the Rhizoctonia root rot nursery in Fort Collins over several years of testing. The method can be used for the selection of individuals exhibiting superior root rot resistance from a segregating population. Evaluation of progeny in a segregating population using the assay can improve the accuracy of root rot resistance scoring for use in molecular marker mapping programs. A preliminary characterization of resistance gene candidates (RGCs) amplified by the polymerase chain reaction that differ between plants exhibiting root rot resistance and root rot susceptibility is presented.