Reactions of Citrullus amarus and Cucumis metuliferus to Meloidogyne chitwoodi, Meloidogyne enterolobii and Meloidogyne luci

Meloidogyne chitwoodi, M. enterolobii, and M. luci are present in some EU countries, with restricted distributions, and plant resistance can be used to manage these nematodes. Two pot experiments were conducted under controlled conditions for 56 d to assess the host suitability of two potential rootstocks, Cucumis metuliferus BGV11135 and Citrullus amarus BGV5167, to one isolate of each nematode. The susceptible cucumber (Cucumis sativus) ‘Dasher II’, watermelon (Citrullus lanatus) ‘Sugar Baby’ and tomato (Solanum lycopersicum) ‘Coração-de-Boi’ were included for comparisons. A histopathological study using confocal-laser microscopy was also conducted 15 d after nematode inoculations. In the pot test, the rootstocks showed lower numbers of galls, egg masses, and eggs per plant than their susceptible ones. Reproduction indices of the rootstocks varied from immune to moderately resistant, depending on the isolate-rootstock combination. In the histopathological study, M. enterolobii and M. luci induced similar numbers of giant cells (GC) per feeding site in all germplasms. However, GC volumes and numbers of nuclei in rootstocks were lower than in the susceptible germplasms. GCs induced by M. chitwoodi were only detected in susceptible cucumber. These results emphasize the potential of C. metuliferus and C. amarus as effective, eco-friendly strategies for managing root-knot nematodes, and show the complex these host-pathogen interactions.