Development of high-gossypol cotton plants with low-gossypol seeds using trispecies bridge crosses and in vitro culture of seed embryos

The objective of this work is to develop an upland cotton, Gossypium hirsut um L. [2n = 4x = 52, 2(AD)(h)], having a reduced level of gossypol in the s eeds for food and feed uses, and a high level of gossypol in the remaining organs to limit pest incidence. Using G. sturtianum Willis (2n=2x=26, 2C(1) ) as donor and G. thurberi Torado (2n = 2x= 26, 2D(1)) or G. raimondii Ulbr ich (2n = 2x = 26, 2D(5)) as bridge species, two trispecies hybrids G. thur beri-G. sturtianum-G. hirsutum and G. hirsutum-G. raimondii- G. sturtianum were synthesized. Both trispecies hybrids were male sterile. Recurrent back crossing to G. hirsutum as pollinator and selfing of the second backcross ( BC) progenies resulted in seeds which were rescued by in vitro culture. In total, 1208 flowers of the trispecies hybrids and their BC progenies yielde d 192 seed embryos from which 62 plants were obtained. Cytogenetic analyses indicated a relatively high frequency of chromosome pairing and chiasmata. The gland levels in backcross seeds ranged from glandless seeds to normall y glanded seeds. All vegetative parts of those hybrids were glanded, but a wide range of variability for gland density was observed on leaf, stem, bra ct and calyx. Plants derived from seeds having a reduced level of gossypol constitute very interesting germplasm to develop a cultivated glanded cotto n with low-gossypol seeds.