Resistance to southwestern cotton rust was successfully transferred to a Gossypium hirsutum L. background in 1968 by L.M. Blank who reported the trait as being simply inherited. Subsequent to this report a source of resistance from Blank's germplasm was incorporated into and utilized in the TAM-MAR (Multi-adversity resistance) breeding program. The resulting strains were screened for resistance and differential disease responses in various morphological structures of the cot-ton plant were observed. An investigation was conducted to elucidate the manner of resistance expression in the cotyledons, petioles, and stems of the MAR cottons. Four strains, two possessing Blank's source of resistance, were selfed and crossed to produce parent, F(l), F₂, and BC populations for the study.