Sugar beet activities of the USDA-ARS East Lansing 2019

Authors: Hanson, Linda; MCGRATH, J MITCHELL - Retired ARS Employee; MINIER, DOUG - Michigan State University; Martin, Frank; MALINI, JAYAWARDANA - Michigan State University; Goodwill, Tom; CORDER, HOLLY - Michigan State University

Submitted to: Annual Beet Sugar Development Foundation Research Report
Publication Type: Research Notes
Publication Acceptance Date: 4/23/2020
Publication Date: 9/1/2020
Citation: Hanson, L.E., McGrath, J., Minier, D.H., Martin, F.N., Malini, J., Goodwill, T.R., Corder, H. 2020. Sugar beet activities of the USDA-ARS East Lansing 2019. Annual Beet Sugar Development Foundation Research Report. Version 1.0. Denver, CO: Beet Sugar Development Foundation.

Interpretive Summary: Two disease nurseries, one each for Cercospora leaf spot (CLS) and Rhizoctonia root and crown rot (RRCR) sugar beet varieties were conducted in 2019. The CLS nursery included entries from two companies and USDA-ARS breeding material for a total of 146 varieties and 62 breeding lines. CLS peaked in late August, after which regrowth outpaced new disease development. Water damage from spring flooding and powdery mildew caused difficulties in rating CLS in some plots. USDA breeding line ratings showed a range of disease severity, including several resistant materials. The RRCR nursery had entries from five companies for a total of 314 sugar beet varieties harvested in August. A range of disease severity was observed. Efforts are being made to develop a screen for Alternaria leaf spot as this is causing economic losses in the region. Little is known about host resistance, so a reliable screening method is needed. Symptoms were observed in the trials but differences were significant only at one testing date, so improvements are needed. The same Alternaria was shown to also infect several other crops, including common rotation crops such as dry bean, an important consideration for management. Finally, testing was done to examine variability in the major root rot pathogen, Rhizoctonia solani, from different geographic regions and hosts. The 78 isolates examined separated into four major genetic groups, with 55% of the isolates examined in one cluster. This was the primary isolate type collected in most growing regions, except the Red River Valley. This type also was the most prevalent on dry bean, a major rotation crop for sugar beet.

Technical Abstract: Two cooperative evaluation nurseries, one for Cercospora leaf spot (CLS) and one for Rhizoctonia root and crown rot (RRCR) evaluation of sugar beet were conducted in 2019. The CLS nursery included entries from two companies, with a total of 146 varieties evaluated as well as 62 USDA-ARS breeding lines. The RRCR nursery had entries from five companies and two controls, with a total of 314 sugar beet varieties evaluated. For the CLS nursery, disease severity peaked in late August, after which regrowth outpaced new disease development. In addition, water damage was an issue in a portion of the field and powdery mildew was present in the field unusually early. This caused difficulties in rating other leaf spots in some plots. USDA breeding line entry ratings averaged 5.5 on a 0-10 scale (where 0 is no leaf spot) and ranged from 3.5 to 7.0 at the last rating (LSD 0.05 = 0.9). The resistant check averaged 4.5 and the susceptible 7.5 at this rating. The RRCR nursery was harvested in August. Disease index means ranged from 3.3 to 5.1 (avg. ~4.3), with controls averaging 4.3 and 4.9 for the moderately resistant and susceptible respectively. Efforts are being made to develop a screen for Alternaria leaf spot as this is increasing in the region. Alternaria leaf spot was observed in the trials but significantly different from the control at only one rating date. The same Alternaria was shown to also infect several other crops, including common rotation crops such as dry bean, an important consideration for management. Finally, testing was done with simple sequence repeats (SSRS) to examine variability in Rhizoctonia solani from different geographic regions and hosts. The 78 isolates examined separated into four major clusters, with 55% of the isolates examined in one cluster. This was the primary isolate type collected in most growing regions, except the Red River Valley. This type also was the most prevalent on dry bean, a major rotation crop for sugar beet.