Relative Susceptibility of Common Cotton Cultivars to Meloidogyne enterolobii , M. floridensis , and M. incognita Isolates from Georgia, U.S.A.

Cotton is a major crop in the southern United States, where Meloidogyne incognita is the most damaging nematode pathogen. Recently, two emerging root-knot nematode species, M. floridensis and M. enterolobii, have been detected in Georgia, raising concerns about their impact on current cotton cultivars. To address this, we evaluated the susceptibility of 12 commercial cotton cultivars to M. enterolobii, M. floridensis, and M. incognita under greenhouse conditions. The susceptible tomato cultivar 'Rutgers' was included as a positive control. Three-week-old cotton plants were individually inoculated with 5,000 eggs of a single nematode species and arranged in a randomized complete block design with six replications. Shoot and root biomass, gall severity, total egg count, and reproduction factor (RF) were assessed. Seven cultivars were resistant (RF M. floridensis, and six were confirmed to be resistant to M. incognita. However, none was resistant to M. enterolobii. Among the three species, M. enterolobii caused the most severe galling and highest nematode reproduction, underscoring its aggressive nature and ability to overcome resistance mechanisms effective against other species. This is the first report to systematically compare and assess cotton cultivar responses to M. floridensis and M. enterolobii, providing critical insight into the species-specific susceptibility of these popular modern cultivars. These findings reveal a major vulnerability in current commercial cultivars and emphasize the urgent need to screen diverse genetic material for novel resistance to M. enterolobii, a rapidly emerging threat to cotton production in the southeastern United States.