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POSTERS: New and emerging diseases

Cotton leafroll dwarf virus: An emerging threat to cotton production in GA
Sudeep Bag - University of Georgia. Peng Chee- University of Georgia, Jared Whitaker- University of Georgia, Nabin Sedhain- University of Georgia, Robert Kemerait- University of Georgia, Afsha Tabassum- University of Georgia, Phillip Roberts- University of Georgia

During fall 2018, cotton plants in several fields in Georgia were observed with symptoms resembling “Cotton blue” disease like leaf curling, reddening and drooping of leaves, subsequent distortion of leaf growth and shortening of upper internodes and their discoloration to deep green. The disease is caused by phloem-limited Cotton leafroll dwarf virus (CLRDV), transmitted by aphids. Symptomatic and asymptomatic leaves tissues were collected from different cotton growing regions in Georgia. Using the three different sets of specific primers, products of predicted sizes were amplified from the symptomatic tissues, but not from asymptomatic tissues collected from the fields. The complete genome of the virus is elucidated by primer walking and small RNA sequencing. Based on the sequences available, the virus detected from the symptomatic tissues is closely related to the South American CLRDV isolates. In 2018, the virus was detected from fourteen counties across the coastal plains of Georgia. In January 2019 commonly growing winter weeds, cotton stalks surviving through the winter and cotton regrowth from the previous crop were collected to understand the disease epidemiology. Preliminary results suggest that the virus could overwinter in the winter weeds and cotton stalks that survived the winter, potentially act as “green bridge” and virus reservoir. Understanding this could help us disrupt the disease cycle and develop management recommendation for this emerging virus. The yield loss due to the virus disease and the role of overwintering hosts need to be investigated.