To introgress fiber quality from Gossypium mustelinum, F1, F2, BC1F1, BC1F2 generations were developed along with random-mating populations at the BC1 generations, i.e., the BC1rm1 and BC1rm2 populations. These random-mating generations were developed using Ms4-TM-1, an isoline heterozygous for Ms4, a dominant nuclear gene for male sterility. These generations were grown in a randomized complete block design with four replications in College Station, Texas during 2003 and 2004, and with three replications in Mexico during winter of 2005/2006. It was found that introgression barriers included daylength sensitivity and hybrid breakdown in selfed generations and that backcross generations had improved fiber quality over TM-1. The effects of hybrid breakdown were not clear in College Station, because of overall low yields due to day-length sensitivity, but was apparent in Mexico where under short days the F1 yielded on average 82.3 g/plant more then the F2 and the BC1F1 yielded 93.6 g/plant more than the BC1F2 population. Random-mating populations did not have increased variance for most traits and means means remained close to BC1F1 levels for most traits. Simple genetic models predicted that the mean for random-mating populations would be equal, which is what was observed. Microsatellite markers showed decreased frequency of G. mustelinum alleles and decreasing heterozygosity, but no increase in map distances in random-mating generations.