Screening and host suitability assessment of nematicidal plants for root-knot nematode control

Summary Root-knot nematodes (RKN), Meloidogyne species, are a top global threat associated with economic crop yield losses. They are difficult to detect and control, especially given the recent restrictions on environmentally harmful chemicals. There is a need for alternative solutions for sustainable RKN management, such as nematicidal plants (non-hosts or poor hosts). Despite extensive research, gaps remain in the understanding of nematicidal plant species and cultivars. Using our method, we evaluated the host suitability of 21 nematicidal plant candidates in climate chambers or glasshouses using a susceptible tomato control. Assessment was based on egg mass counts after one RKN cycle, as an indicator of reproduction. All the 21 candidates screened against Meloidogyne incognita were less infected than tomatoes, suggesting all the candidates are either non- or poor hosts. Tagetes species were evaluated against M. incognita , M. arenaria and M. enterolobii , with T. patula and T. erecta consistently non-hosts to the three RKN species. We also evaluated the number of galls as an indicator of the initiation of the RKN feeding sites and the plant’s reaction. Only Tagetes spp. had no galls. Tagetes species Foeniculum vulgare and Crotalaria juncea were further assessed for M. incognita juvenile penetration and had significantly lower penetration than tomato, except for C. juncea . This suggests all Tagetes species and F. vulgare inhibit root penetration of most M. incognita juveniles at the rhizosphere level, while C. juncea attracts the nematodes and restricts reproduction. There is potential for most of the nematicidal plants to be used in cropping systems for sustainable integrated RKN management.