Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2010
Publication Date: April 12, 2010
Citation: Hanson, L.E., Duckert, T.M., Goodwill, T.R., McGrath, J.M. 2010. Beta PIs From the USDA-ARS NPGS Evaluated for Resistance to Cercospora beticola, 2009. Plant Disease Management Reports. Available: http://www.plantmanagementnetwork.org/pub/trial/PDMR/reports/2010/FC005.pdf Interpretive Summary: Cercospora leaf spot is one of the most widespread and destructive fungal disease of beet and occurs wherever beets are grown. One important method of managing the disease is the use of varieties with resistance to the pathogen, Cercospora beticola. In an ongoing effort to find sources of resistance to Cercospora, 30 Plant Introdcutions (PIs) from the USDA-ARS National Plant Germplasm System were tested for their response to the leaf-spotting fungus, Cercospora beticola. Disease development was moderate and the disease was not severe enough to rate until mid-August. Significant variability was detected between different entries. Three PIs were not significantly different from the resistant control at all rating dates. A large number of the PIs produced seed stalks during the study and these had to be removed. Only seven PIs did not need to have seed stalks removed, and for two, so much tissue had to be removed that for at least one replicate, ratings could not be made at one or more of the later rating dates.
Technical Abstract: Thirty Plant Introductions (PIs) from the USDA-ARS National Plant Germplasm System were evaluated for resistance to Cercospora beticola in an artificially produced epiphytotic at the Saginaw Valley Research Farm near Frankenmuth, MI. Internal controls included a susceptible commercial variety, CE, and a resistant variety, ACH 355. The field was planted May 5, with a delay due to wet spring weather. The nursery was inoculated once with a liquid spore suspension of Cercospora beticola. Visual evaluations on the plot, producing a disease index (DI) on a scale from 0 (no disease) to 10 (plant dead), were made on five dates, with the peak of the epidemic occurring between the fourth and fifth dates. After the fifth date, cool night time temperatures allowed regrowth of several PIs, so ratings started to go down. At our fourth evaluation, means of the resistant and susceptible internal control were 2.5 and 5.3, respectively, across the nursery. In 2008, these means were 2.4 and 5.2, respectively. Means of the PIs ranged from 3.0 to 5.3. An analysis of variance on the disease indices determined that there were significant differences among entries (P=0.05) on all five dates of evaluation. Five accessions were not significantly different from the resistant control at all five rating dates. Roots were collected to use in the ARS Cercospora breeding program