This is a long term cotton breeding and marker development project spanning several years. The objective is to develop and release a package of breeding lines and genetic markers that will allow the cotton seed industry to quickly develop cotton cultivars with high levels of resistance to the reniform nematode. Resistance is being introgressed from immune G. longicalyx by utilizing two triple species hybrids as bridges between G. longicalyx and G. hirsutum. The project integrates interactive components focused on breeding, resistance evaluation, cytogenetic analysis, field evaluation, and marker development to maximize speed and likelihood of success. During the last 2 years since our last progress report on the breeding component of the project at the Beltwide Conferences, we have advanced 28 progeny lines through several backcross generations, achieving in various backgrounds highly resistant, cytogenetically normal heterozygous plants that are morphologically indistinguishable from agronomic G. hirsutum under greenhouse conditions. Normal recombination rates would predict these plants to contain less than 1% foreign germplasm; at this point, however, marker and genome in situ hybridization data is preliminary and we cannot reliably estimate the size of the alien segments containing the resistance gene(s). We have, however, examined progeny from selfed heterozygous parents under field and greenhouse conditions to test for presence of deleterious recessive traits in plants homozygous for the resistance, and results are encouraging. We also have made considerable initial progress toward the development of AFLP markers cosegregating with resistance.