The Relationships Between Population Density of Meloidogyne Incognita and Nicotine Content of Tobacco1)

Seedlings of Meloidogyne incognita resistant (NC 95) and susceptible (McNair 30) tobacco cultivars were grown in 15 cm clay pots containing steamed soil infested with 0, 4, 16, and 64 eggs of M. incognita per 1.5 cc soil. Dry root weight of NC 95 and McNair 30 decreased from 22 g to 15 g and from 24 g to 0.8 g, respectively, as nematode density was increased from 0 to 64 eggs per 1.5 cc soil. Sixteen amino acids, including precursors for nicotine, and nicotine increased significantly in roots of NC 95 and McNair 30 as nematode density was increased. Nicotine content increased 77% and 56% in roots of NC 95 and McNair 30 respectively as the initial nematode density was increased from 0 to 64 eggs per 1.5 cc soil. Leaf-nicotine content increased from 0.9% to 1.5% in NC 95, and decreased from 0.8% to 0.7% in McNair 30 as nematode density was increased from 0 to 64 eggs per 1.5 cc soil. As nematode density was increased, roots of NC 95 were not damaged significantly, and higher nicotine content in infected roots resulted in higher nicotine levels in the leaves because nicotine translocation apparently was not restricted. In McNair 30 severe root damage by increased nematode density probably decreased nicotine movement to vegetative organs.