Identification and Virulence of Five Isolates of Root-Knot Nematode Meloidogyne floridensis on Vegetables

Meloidogyne floridensis is of particular concern because it reproduces on tomato, pepper, corn, and tobacco cultivars that have resistance to the common tropical root-knot nematode (RKN) species (i.e., Meloidogyne incognita, M. arenaria, and M. javanica). During a survey of 436 randomly selected vegetable fields in Georgia in 2018, 6 M. floridensis-infested fields were found and cultured from single egg-mass isolates on a susceptible tomato (cultivar Rutgers), and speciated using molecular analyses. Five isolates of M. floridensis were identified from collard, cowpea, cucumber, watermelon, and tomato fields by DNA sequence-based identification targeting mitochondrial genes (cytochrome c oxidase subunit II, transfer RNA, large subunit ribosomal RNA, and NADH dehydrogenase subunit 5). Two greenhouse trials determined the host preference and reproduction level for each M. floridensis isolate. Evaluations were conducted on Rutgers tomato, a resistant tomato (cultivar Skyway, carrying the Mi-1.2 gene), and vegetable crops associated with the origin of M. floridensis populations. This study confirmed that most associated vegetables, except collards, were good hosts to M. floridensis, having a reproduction factor >1. All isolates were able to reproduce aggressively on the resistant tomato. We found variations among M. floridensis isolates in pathogenicity and reproduction levels on the vegetable crops tested which should be considered when using or developing host resistance.