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ARS Home » Midwest Area » East Lansing, Michigan » Sugarbeet and Bean Research » Research » Publications at this Location » Publication #323982
Title: Beta PIs from the USDA-ARS NPGS evaluated for resistance to Cercospora beticola, 2015

Author
item Hanson, Linda
item Goodwill, Tom
item McGrath, Jon

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2015
Publication Date: 3/7/2016
Citation: Hanson, L.E., Goodwill, T.R., McGrath, J.M. 2016. Beta PIs from the USDA-ARS NPGS evaluated for resistance to Cercospora beticola, 2015. Plant Disease Management Reports. 10:FC022.

Interpretive Summary: Cercospora leaf spot is a destructive fungal disease of beet and occurs in most beet production areas. One important method of managing the disease is the use of varieties with resistance to the pathogen, Cercospora beticola. In continuing efforts to identify 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. An additional seven entries resulting from crossing of previous years (2008-2013) PIs selected from Cercospora leaf spot tests with USDA germplasm were included for evaluation. Plants were inoculated July 2 and the disease was severe enough to start rating by mid August. Significant variability was detected in disease severity between different entries. Three PIs and two of the entries from crossing tests were not significantly different from the resistant control at the first rating date, but all entries had significantly higher disease severity than the resistant control at the four later rating dates. Eleven PIs and six of the crossing entries had significantly lower disease levels than the susceptible control. Only two of the PIs produceed seed stalks (i.e. were annual) during the study. Materials identified in these screenings may be useful sources for resistance breeding and expanding genetic diversity in this crop as indicated by crosses with materials from previous years screening.

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 and Extension Center near Frankenmuth, MI. An additional seven entries resulting from crossing of previous years (2008-2013) PIs selected from Cercospora leaf spot tests with USDA germplasm were included for evaluation. Internal controls included a susceptible, '12N0050', and a resistant germplasm 'EL50/2'. The field was planted April 30. The nursery was inoculated once with a liquid spore suspension of Cercospora beticola on July 2. Visual evaluations on the plot, producing a disease index (DI) on a scale from 0 (no disease) to 10 (plant completely defoliated), were made on five dates, with the peak of the epidemic occurring around the fifth date. At and after the fifth rating, regrowth of several PIs was visible, so ratings started to go down. At our fifth evaluation, means of the resistant and susceptible internal control were 3.2 and 7.0, respectively, across the nursery. In 2014 these means were 2.4 and 5.8, respectively. Means of the PIs ranged from 4.0 to 7.3. An analysis of variance on the disease indices determined that there were significant differences among entries (P=0.05) on all dates of evaluation. Three PIs and two of the entries from crossing tests were not significantly different from the resistant control at the first rating date, but all entries had significantly higher disease severity than the resistant control at the four later rating dates. Eleven PIs and six of the crossing entries had significantly lower disease levels than the susceptible control. Only two of the PIs produceed seed stalks, meaning they had an annual growth habid. Some of the materials may be useful sources for resistance breeding and increasing genetic diversity in this crop.