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Title: Beet curly top resistance in USDA-ARS Ft. Collins Germplasm, 2012

Author
item Panella, Leonard
item Strausbaugh, Carl

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2013
Publication Date: 8/14/2013
Citation: Panella, L.W., Strausbaugh, C.A. 2013. Beet curly top resistance in USDA-ARS Ft. Collins Germplasm, 2012. Plant Disease Management Reports. 7:FC120.

Interpretive Summary: Seventeen sugar beet lines from the USDA-ARS Ft. Collins sugar beet program were screened for resistance to Beet severe curly top virus (BSCTV) and other closely related Curtovirus species in 2012. Commercial sugar beet cultivars Monohikari and HM PM90 were included as susceptible and resistant checks, respectively. The curly top evaluation was conducted at the USDA-ARS North Farm in Kimberly, ID. The germplasm was planted on 21 May. Plant populations were thinned on 19 Jun. Plants were inoculated at the four to six leaf growth stage on 22 Jun with six virus infected beet leafhoppers per plant. The plants were sprayed with Lorsban on 4 Jul to kill the beet leafhoppers. The plots were rated for leaf symptoms on 10 Jul using a scale of 0-9 (0 = healthy and 9 = dead). Leaf samples were also pulled at the time of disease rating and evaluated in an ELISA assay. Disease development was uniform and other disease problems were not evident in the plot area. The disease pressure in the test was severe with good symptom development in the susceptible check. A number of the lines were not significantly different from the resistant check based on both visual symptoms and ELISA, indicating these lines had true resistance to the virus and not just tolerance. The resistant check was not completely resistant since it had symptoms and an ELISA value that was six times higher than the negative background checks. Thus, there is still room for improving resistance to the curly top virus species.

Technical Abstract: Seventeen sugar beet (Beta vulgaris L.) lines from the USDA-ARS Ft. Collins sugar beet program were screened for resistance to Beet severe curly top virus (BSCTV) and other closely related Curtovirus species in 2012. Commercial sugar beet cultivars Monohikari and HM PM90 were included as susceptible and resistant checks, respectively. The curly top evaluation was conducted at the USDA-ARS North Farm in Kimberly, ID which has Portneuf silt loam soil and had been in alfalfa in 2011. The field was plowed in the fall and in the spring, fertilized (90 lb N and 110 lb P2O5/A) on 16 Apr 12, sprayed with Ethotron (2 pt/A), and roller harrowed. The germplasm was planted (density of 142,560 seeds/A) on 21 May. The plots were two rows 10 ft long with 22-in row spacing and arranged in a randomized complete block design with four replications. The fields were sprinkler irrigated and hand weeded as necessary. Plant populations were thinned to about 47,500 plants/A on 19 Jun. Plants were inoculated at the four to six leaf growth stage on 22 Jun with six viruliferous beet leafhoppers per plant. The beet leafhoppers were moved twice a day (right after sunrise and just before sunset) for one week by dragging a tarp through the field. The plants were sprayed with Lorsban 4E (1.5 pints/A) on 4 Jul to kill the beet leafhoppers. The plots were rated for foliar symptom development on 10 Jul using a scale of 0-9 (0 = healthy and 9 = dead), with the scale treated as a continuous variable (Plant Dis.:90:1539-1544). Leaf samples were also pulled at the time of disease rating and evaluated in an enzyme-linked immunosorbent assay (ELISA) as described previously (Plant Dis. 94:972-976). Data were analyzed using the general linear models procedure (Proc GLM-SAS), and Fisher’s protected least significant difference (a = 0.05) was used for mean comparisons. Disease development was uniform and other disease problems were not evident in the plot area. The disease pressure in the test was severe with good symptom development in the susceptible check. A number of the lines were not significantly different from the resistant check based on both visual symptoms and ELISA, indicating these lines had true resistance to the virus and not just tolerance. The resistant check was not completely resistant since it had symptoms and an ELISA value that was six times higher than the negative background checks. Thus, there is still room for improving resistance to the curly top virus species.