Beta vulgaris lines from USDA-ARS Kimberly evaluated for resistance to Cercospora beticola, 2016

Authors: Eujayl, Imad; Vincill, Eric; Strausbaugh, Carl; Hanson, Linda

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2022
Publication Date: 8/9/2022
Citation: Eujayl, I.A., Vincill, E.D., Strausbaugh, C.A., Hanson, L.E. 2022. Beta vulgaris lines from USDA-ARS Kimberly evaluated for resistance to Cercospora beticola, 2016. Plant Disease Management Reports. 16: V135.

Interpretive Summary: In 2016, six sugar beet germplasm lines from the USDA-ARS Kimberly program were screened for resistance to Cercospora beticola. The Cercospora leaf spot (CLS) evaluation was conducted at the Michigan State University Saginaw Valley Research and Extension Center (SVREC) near Frankenmuth, MI in a field that had been planted in wheat with clover underseeded in 2015. The plots were rated for foliar symptom development on 6 Sep. using a scale of 0 to 10 (0 = healthy and 10 = all leaves dead). The checks performed as expected for the visual rating. Statistically, five of the entries contain at least moderate resistance since their visual ratings were at least as good as the moderate and resistant checks. However, entry 3 was better than the resistant check and entries 4, 5, and 6 were equal to the resistant check. These data confirm what had been determined the previous year, so these lines will be incorporated into the USDA-ARS germplasm improvement program as a source of resistance to CLS.

Technical Abstract: In 2016, six sugar beet (Beta vulgaris L.) germplasm lines from the USDA-ARS Kimberly program and 2 check lines [EL50/2 (resistant) and F1042 (susceptible)] were screened for resistance to Cercospora beticola. The Cercospora leaf spot (CLS) evaluation was conducted at the Michigan State University Saginaw Valley Research and Extension Center (SVREC) near Frankenmuth, MI in a field that had been planted in wheat with clover underseeded in 2015. The germplasm was planted on 6 May and thinned by hand as necessary. Single-row plots 4.5 m long with 51 cm between row spacing were planted with the treatments arranged in a randomized complete block design with four replications. Quadris 2.08SC (azoxystrobin) was applied at 0.0091 kg/100 m row in a 14 cm band in-furrow at planting to control Rhizoctonia damping-off. Weeds were controlled by a preplant application of ethofumesate 9 May, four times with mixtures of phenmedipham, desmedipham, triflusulfuron methyl, and clopyralid (18 and 23 May, 10 Jun., and 21 Jun), and once with S-metolachlor (29 Jun). The herbicide spray treatments had to also be supplemented with hand weeding. The nursery was spray inoculated on 5 Jul. with a liquid spore suspension (1 x 103 spores/ml) of C. beticola. The inoculum was produced from a mixture of leaves collected from the 2015 CLS nursery at SVREC and from naturally infected sugar beets grown at SVREC and on the Michigan State University campus farms in East Lansing, MI. The plots were rated for foliar symptom development on 6 Sep. using a scale of 0 to 10 (0 = healthy and 10 = all leaves dead; J. Am. Soc. Sugar Technol. 16:284). Data were rank transformed prior to analysis in SAS (Ver. 9.4) with mixed linear models (Proc MIXED), but the non-transformed means have been presented in the table. Mean separation was based on a PDIFF comparison with a probability cutoff of 0.05. Cercospora leaf spot development was uniform and moderate and other disease and pest problems were evident in the plot area. The checks performed as expected for the visual rating. Statistically, five of the entries contain at least moderate resistance since their visual ratings were at least as good as the moderate and resistant checks. However, entry 3 was better than the resistant check and entries 4, 5, and 6 were equal to the resistant check. These data confirm what had been determined the previous year, so these lines will be incorporated into the USDA-ARS germplasm improvement program as a source of resistance to CLS.