Excised Tobacco Pith Bioassays for Root-knot Nematode-produced Plant Growth Substances

Root-knot nematodes, Meloidogyne incognita, were grown in tobacco pith tissue cultured in vitro on modifired white's medium. The nematodes did not secrete detectable amounts of auxin or cytokinin, but did promote growth in the presence of both types of growth substance. When both IAA and kinetin were supplied, the nematode-infected tissue was larger, more irregularly shaped than control tissue; nematodes induced syncytia and developed past the second larval stage. When either IAA or kinetin was omitted from the medium, nematodeinfected and control tissue failed to grow and the nematodes failed to induce syncytia or develop.