The present study on the plant nematodes associated with Bt cotton crop growth in northern Karnataka, India covered several aspects like a nematode random survey in Bt cotton-growing areas of the state, nematode community analysis, pathogenicity and biology of a dominant nematode and reaction of Bt cotton cultivars and hybrids to that nematode. A random survey undertaken in the Bt cotton-growing districts of northern Karnataka for the associated nematodes in
cotton rhizosphere soil and root samples showed the presence of plant pathogenic nematodes, mainly reniform nematode (Rotylenchulus reniformis), lesion nematode (Pratylenchus sp.) and some dorylaimid pathogens. Other plant pathogenic species were present in less numbers.