Two Upland (Gossypium hirsutum) varieties (Kapas Purao and Philippines Ferguson) and apunctatum cotton of unknown origin, were all shown to carry a key hairiness gene at theH1 locus. This gene is so closely linked withchl1 (one of the two complementary genes governing chlorophyll deficiency) that transferences of it to Sakel, which carrieschl2, cannot produce strains homozygous for hairiness. This allele has been calledH1k, and it is considered probable that theH1k-chl1 segment of chromosome is invertedvis-à-vis theH1-Chl1 segment in Sakel and inG. barbadense in general, andvis-à-vis theH1-chl1 segment in MU8b and otherG. hirsutum varieties.
In addition toH1k, Ferguson carries modifying genes which lengthen the hairs, minor H genes which can themselves directly confer hairiness, and modifying genes reducing the density of hair population.