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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. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the effects of Hirsutella minnesotensis (Hm), an endoparasitic fungus, and N-Viro Soil® (NVS), a recycled municipal biosolid, on Meloidogyne hapla greenhouse populations from Rhode Island (RI), Connecticut (CT), Geneva, New York (NYG), Lyndonville, New York (NYL), and Michigan (MI). In a greenhouse experiment, tomato (cv. Rutgers) seedlings were inoculated with 0 or 600 eggs of each nematode population and exposed to Hm mycelium (0 or 0.1 g fresh) and NVS (0 or 1 g 0.1 L-1 of soil) in a factorial design. Hirsutella minnesotensis reduced nematode densities by 31-83% across nematode populations in one test, but only slightly reduced densities of NYG and CT populations in another test. NVS reduced nematode densities by 33-92% across populations in two repeated tests. The combination of the two agents resulted in greater nematode reduction compared with Hm alone, but not compared with NVS alone. Across all Hm and NVS treatments, reduction of nematode densities were generally greater in NYG, CT, and RI than in MI and NYL populations. This study demonstrated that Hm and NVS may be used to suppress different M. hapla populations. [ABSTRACT FROM AUTHOR]

The relative susceptibility of 44 genotypes of wild Fragaria L. and commercial cultivars of strawberry Fragaria xananassa Duch to Meloidogyne hapla Chitwood and Pratylenchus penetrans (Cobb) Filipjev & Shuurmans Stekhoven was evaluated in the greenhouse. Eleven genotypes were highly resistant to populations of M. hapla from Washington State and Oregon, with Rf values (initial nematode density/final population density) less than 0.5. However, root growth of most genotypes, including resistant genotypes, was reduced by M. hapla. Thirteen genotypes were ranked more resistant to P. penetrans than F. xananassa 'Totem', a susceptible cultivar. Root growth of most genotypes was not affected by P. penetrans under these experimental conditions. We conclude that commercial cultivars and wild Fragaria genotypes can provide a readily exploitable source of resistance to M. hapla. Conversely, sources of resistance to P. penetrans were uncommon in the germplasm evaluated. The F. xananassa cultivars, which already have commercially important characteristics, appear to be a better source of resistance for both nematode species than the wild, unimproved germplasm. [ABSTRACT FROM AUTHOR]