Meloidogyne floridensis has a unique virulence profile against root-knot nematode resistant and susceptible

Authors: KHANAL, CHURAMANI - Clemson University; Rutter, William; ALAM, MD - Clemson University; ALARCON-MENDOZA, I - Clemson University

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/24/2024
Publication Date: 3/13/2025
Citation: Khanal, C., Rutter, W.B., Alam, M.S., Alarcon-Mendoza, Meloidogyne floridensis has a unique virulence profile against root-knot nematode resistant and susceptible. Journal of Nematology. Volume 57 (2025):Issue 1 https://doi.org/10.2478/jofnem-2025-0007.
DOI: https://doi.org/10.2478/jofnem-2025-0007

Interpretive Summary: The peach root knot nematode (PRKN, Meloidogyne floridensis) is a recently described species of nematode that has been found infecting and damaging a number of specialty crops in the southeastern U.S. as well as in California. Although PRKN is closely related to other root-knot nematode species such as the more common southern root-knot nematode (SRKN) it is unique its ability to infect and damage many of the most common SRKN resistant variates of peach, tomato, and pepper. In this study we set out to further characterize the virulence of PRKN by conducting greenhouse tests on additional SRKN resistant pepper lines with known sources for resistance. Our results show that PRKN is virulent on all known sources of SRKN resistance in pepper. Surprisingly, we also found that one USDA line, PA136, that was previously thought to be universally susceptible to all root knot nematode species, is actually highly resistant to PRKN. Further testing of hybird lines indicates that PA136 likely carries a dominant gene that confers species specific resistance to PRKN. These results further highlight the distinct virulence profile of PRKN relative to other closely related RKN species in the southern US, and provides a new source of resistance that could be used to develop new PRKN resistant pepper lines.

Technical Abstract: Meloidogyne floridensis is a recently described species of root-knot nematode (RKN) that is very closely related to the most common and damaging species in this genus, including M. incognita. Despite its close phylogenetic relationship, M. floridensis is distinctive from its close relatives in both its facultatively sexual lifestyle and its documented virulence on many of the most common RKN resistance genes in cultivated peach, tomato, and pepper. To further characterize the virulence profile of M. floridensis, we conducted replicate greenhouse screens using this nematode to infect a panel of pepper lines that carry different sets of known RKN resistance genes. Although our isolate of M. floridensis was virulent against all the most common RKN resistance genes, including N, Me1, and Me3, we found that one of the lines that was previously thought to contain no RKN resistance, PA 136, was highly resistant to this nematode. Further testing of an F1 hybrid of this line confirmed this result and indicated that PA 136 contains an as yet uncharacterized and potentially dominant source of species-specific resistance against M. floridensis. These surprising results provides additional data on the differences between M. floridensis and its close relatives, and identifies new sources of resistance that could be used as management tools against this nematode.