Based on the study of cytogenetic features of triploid hybrid G.arboreum x G.palmerii, methods of experimental polyploidy were improved, methods of vegetative reproduction of hybrids were developed, and also the possibility of using the hexaploid G.hursutum x G.sturtii in breeding were studied. No naturally occurring forms of hexaploid G.arboreum x G.palmerii with 78 chromosomes were derived for the first time. By reciprocal backcrossing of hexaploid forms pentaploid forms with 65 chromosomes were derived, and they were used as rich donors for creation of intensive varieties. As a result of these studies a number of promising lines with traits of both G.arboreum and G.sturtii distinquishing by high quality fiber were obtained. Currently, these lines are given to the Department of Plant Breeding at the Institute of Cotton Growing.