Interspecific hybridization in cotton and its use in breeding

Abstract. Interspecific hybridization in cotton is of great importance with a view to exploit the diversity of species in the genus Gossypium L. The aim of thisstudy was to use the genetic potential of wild species of the genus Gossypium L. to improve productivity, fiber quality and resistance to some stressors of themodern Bulgarian cotton varieties. Interspecific hybridization of Gossypium hirsutum L. species (2n=52) with the wild diploid species G. sturtii F. Muell., G.thurberi Tod., G. davidsonii Kell. and G. raimondii Ulbr.(2n=26) was realized. To overcome sterility, caused by incompatibility of the genomes, the growing tips ofthe F plants in phase cotyledons were treated with 0.1% solution of colchicine for 12 hours. Amphidiploids of the G. hirsutum × G. sturtii, G. hirsutum × G. 1thurberi and G. hirsutum × G. davidsonii, and trispecific hybrids G. hirsutum - G. arboreum - G. raimondii, G. hirsutum - G. arboreum - G. thurberi and G.hirsutum - G. thurberi - G. raimondii were obtained. To overcome the undesirable qualities that hybrids inherited together with desirable ones from the wildspecies two- or three-times backcrossing in C and F (at the triple hybrids) and in the later generations was applied. Studies carried out with this hybridization 1 1revealed a number of opportunities such as to increase productivity, to improve fiber quality, resistance to low positive temperatures, drought tolerance, toobtain new valuable traits. After backcrossing to the cultivated species valuable introgressed forms having high productivity (from the hybridization with G.thurberi), high strength of the fiber and resistance to aphids and thrips (from the hybridization with G. sturtii), drought-tolerance or resistance to low positivetemperatures, etc., were obtained.