Alejandra M. Jimenez Madrid, PhD (she/her/hers)
Director Plant Molecular Diagnostic Lab
University of Georgia
Tifton, Georgia, United States
Tessie Wilkerson
Mississippi State University, Delta Research and Extension Center
Stoneville, Mississippi, United States
Tom W. Allen
Extension/Research Professor
Delta Research & Extension Center, Mississippi State University
Stoneville, Mississippi, United States
Heather Marie Kelly, n/a
Professor
University of Tennessee
Jackson, Tennessee, United States
Teddy Garcia-Aroca, PhD
Assistant Professor
Department of Plant Pathology, University of Nebraska-Lincoln
Lincoln, NE, USA
Robert C. Kemerait, Jr., PhD
Professor
UGA Dept of Plant Pathology
Tifton, GA, USA
Areolate mildew, previously reported to be caused by two species of Ramulariopsis (R. gossypii and R. pseudoglycines), is an important resurgent disease of cotton in the southern U.S. Until recently, this disease was considered of secondary importance, but the recent prevalence and high incidence observed in this region have caused concerns. To characterize the species associated with areolae mildew in the U.S., a survey was initiated in 2024. Isolates of Ramulariopsis spp. from Georgia (n=23), Mississippi (n=24), and Tennessee (n=15) were tested for species identification by sequencing the TEF 1-α region. Previous research has reported that timely applications of quinone outside inhibitor (QoI) fungicides have been effective in managing this disease; however, a reduced efficacy has been observed in locations in GA, hence, monitoring QoI resistance development is critical. TEF sequencing results revealed that all isolates tested belong to R. pseudoglycines, confirming the widespread nature of this species in the southern U.S. The partial amplification of the cytB gene showed that only isolates from one GA County had the G143A substitution. To further understand the biology of the pathogen and develop a rapid diagnostic assay, a whole genome of R. pseudoglycines (~77.9 Mb) was assembled using a nanopore platform to serve as a reference genome. Results from this survey will serve as a baseline for monitoring and detecting the species associated with this disease in the U.S. as well as understanding the development of QoI resistance within the pathogen population