Sugar beet activities of the USDA-ARS East Lansing conducted in cooperation with Saginaw Research & Extension Center during 2020

Authors: Hanson, Linda; CORDER, HOLLY - Michigan State University; Goodwill, Thomas; JAYAWARDANA, MALINI - Michigan State University

Submitted to: Saginaw Valley Bean and Beet Farm Report
Publication Type: Research Technical Update
Publication Acceptance Date: 3/8/2021
Publication Date: 4/1/2021
Citation: Hanson, L.E., Corder, H.J., Goodwill, T.R., Jayawardana, M.A. 2021. Sugar beet activities of the USDA-ARS East Lansing conducted in cooperation with Saginaw Research & Extension Center during 2020. Saginaw Valley Bean and Beet Farm Report. Pgs 97-102.

Interpretive Summary:

Technical Abstract: Evaluation and rating plots were planted at the Saginaw Valley Research & Extension Center (SVREC) in Frankenmuth, MI in 2020 focusing on Cercospora leaf spot, (CLS) and Rhizoctonia root and crown rot (RRCR) disease performance of a range of Beta vulgaris materials and developing inoculation method for Alternaria leaf spot (ALS). CLS and RRCR trials were conducted in conjunction with the Beet Sugar Development Foundation (BSDF) and CLS trials included USDA-ARS cooperator germplasm. All trials were planted following normal fall and spring tillage operations. The BSDF CLS nursery was planted on May 22 wand the BSDF RRCR nursery on May 23, 2020, with a delay due to Covid restrictions. The CLS nurseries were inoculated on July 9 with a liquid spore suspension (approximately 1 x 103 spores/ml) of Cercospora beticola. Inoculum was produced from a mixture of leaves collected from the 2019 inoculated leaf spot nursery at SVREC and naturally infected leaves. Due to low disease development, a second inoculation was performed July 23. CLS severity peaked in late September, after which regrowth started to outpace new disease development. Entry ratings ranged from 3.0 to 6.0 at the last rating. ALS testing included a susceptible and putative moderately resistant germplasm. Inoculum was produced from a culture in the lab and applied as a liquid spore suspension (approximately 1 x 104 spores/ml). Addition of a nutrient solution was tested as greenhouse screening showed it can increase infection. Visual evaluations of the plots were conducted with a disease index (DI) on a scale from 0-10 where 0=no symptoms and 10=all leaves dead. The two varieties showed consistent significant (p=0.03 to >0.001) differences starting at two weeks after inoculation and through the duration of rating. For RRCR, the nursery was inoculated on July 11 with a dry ground barley inoculum of Rhizoctonia solani anastomosis group 2-2. Roots were dug August 11-13. Each root was rated for disease severity using a 0-7 scale where 0=no visible lesions and 7=root completely rotted. A weighted disease index was calculated for each replicate. The disease index means for the 2020 nursery ranged from 4.5 to 6.5, with controls averaging 4.9 and 5.8 for the moderately resistant and susceptible varieties respectively.