Monitoring the Distribution, Incidence, and Symptom Expression Associated with Cotton Leafroll Dwarf Virus in the Southern United States Using a Sentinel Plot System

Cotton leafroll dwarf virus (CLRDV), transmitted by the cotton aphid ( Aphis gossypii Glover), was first confirmed in upland cotton ( Gossypium hirsutum L.) in Alabama, U.S.A., in 2017. Subsequent observations of symptomatic plants followed by virus infection confirmation via reverse transcriptase PCR (RT-PCR) were made in neighboring states in 2018. To assess the distribution and incidence of CLRDV and the occurrence of presumed symptoms across the southern cotton belt, a multidisciplinary team established sentinel plot survey sites at 16 experiment stations in 11 states stretching from Texas to Virginia and Tennessee to Florida beginning in 2019. Field trials were conducted over a 3-year period using multiple cotton cultivars that were adjusted annually. Cotton plots were evaluated at each location by a single evaluator to attempt to correlate symptom occurrence across the cotton-growing region with virus incidence in cotton plant tissues using RT-PCR. Symptom incidence, based on visual estimation of plants in each plot with presumed symptoms, differed across the region and ranged from 0 to 75%, with a low average over all locations of 11.4% in 2021 to an average high of 28.0% in 2020. Though symptom incidence suggested the presence of CLRDV, there were instances where apparent symptoms were observed but virus presence was not confirmed by RT-PCR. CLRDV has since been confirmed from all locations, which suggests that it has become endemic in cotton production areas throughout the eastern range of the United States. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .