Tobacco Resistance to Globodera tabacum.

Two flue-cured tobacco cultivars, VA-81 and PD-4, resistant to Globodera tabacum solanacearum were tested for resistance to G. tabacum in field and greenhouse experiments. A G. tabacum-susceptible broadleaf cultivar CT86-4 was used for comparison. In a greenhouse screening procedure, VA-81 and PD-4 had, respectively, 1 of 24 and 0 of 24 plants with any cysts visible on the root systems. All 24 plants of CT86-4 had at least four G. tabacum cysts visible per plant. Up to 80% of juveniles emerged from cysts in response to all tobacco cultivars transplanted into pots. Subsequent reproduction was much less on VA-81 and PD-4 than on CT86-4. Staining nematodes in roots 5 weeks after inoculation indicated that fewer nematodes had developed in VA-81 and PD-4 than in CT86-4. During one growing season, population densities of G. tabacum in naturally infested field soil declined by 72-80% under VA-81 and PD-4 and increased by 144% under CT86-4.