Exploitation of trispecific hybrids to introgress the glandless seed and glanded plant trait of Gossypium sturtianum Willis into G. hirsutum L.

Two différent trispecific hybrids were developed in order to introgress the "glandless seed-glanded plant" trait of Gossypium sturtianum Will. (2n = 2x = 26, CI genome) into the main cultivated cotton species (Gossypium hirsutum L., 2n = 4x = 52, (AD), genome) using either Gossypium raimondii Ulb. (2n = 2x = 26, D5 genome) or Gossypium thurberi Tor. (2n = 2x = 26, Dl genome) as bridge species. Both trispecific hybrids were backcrossed with two G. hirsutum varieties (C2 and NC8) originating from Zaire. Observation of the trispecific seeds pointed out the incomplets expression of the seed gossypol glands répressive mechanism of G. sturtianum when its chromosomes set is confronted with the D genome. The glandless trait was expressed in a rather high proportion of the BC, seeds: 6 out of 41. Only one of the six BC, glandless seeds gave riss to a viable glanded plant. Cytogenetic observations of both trispecific hybrids and of the introgressed plant confirmed the soundness of the introgression strategy followed. All these plants were euploid (2n = 4x = 52) and showed high frequencies of multivalent and chiasma formations at métaphase I indicating important genetic material exchanges. All the plants issued from nearly totally glandless seeds will be used in a backcrossing program with G. hirsutum to produce commercial varieties of upland cotton expressing the "glandless seed-glanded plant" trait.