Abstract
Meloidogyne hapla Chitwood, the northern root-knot nematode, is a major pest on lettuce (Lactuca spp.) in the northeastern United States. In order to identify resistant germplasm, 494 lettuce accessions (443 L. sativa, 36 L. serriola, 7 L. virosa. and 8 L. saligna) were evaluated in the greenhouse in two trials. Six-week-old Lactuca spp. seedlings were inoculated with 5000 M. hapla eggs per plant and evaluated after 12 weeks. Galling severity and fresh root weight were measured. Of the 443 L. sativa accessions, only two, PI 508476 and PI 419140, repeatedly exhibited a root galling index of ≤2, indicating up to 20% galling, in two screening trials. Four wild Lactuca accessions, L. saligna PI 281876, L. saligna PI 491000, L. saligna 261653, and L. virosa PI 273579, were also considered highly resistant, suggesting that these accessions may be useful in hybrid breeding studies.
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