Production of High Gossypol Cotton Plants with Low Gossypol Seed from Trispecies Hybrids Including G. sturtianum Willis
Feb 11, 2019
Two tri-species hybrids that include G. hirsutum L. (2n=4X=52 (AD genome)) were created to develop upland cotton plants with low gossypol seed and high gossypol aerial parts. G. sturtianum Wil. was used as the donor parent (2n=2x=26, genome C1) and a wild American diploid cotton, G. thurberi Tor. (2n=2x=26, genome D1) or G. raimondii Ulb. (2n=2x=26 genome D5) as bridge species. Both tri-species hybrids were backcrossed to different G. hirsutum varieties, originating from Central and West Africa to produce BC1, BC2, selfed BC2 and BC3 seeds. Growth regulators applications at flowering, in vitro culture of the mature seed embryos and grafting of the more perturbed hybrids on vigorous G. hirsutum seedlings were necessary to obtain a large number of viable hybrid material. A drastic reduction of the gossypol gland density was expressed by at least 25% of the seeds of each backcross generation while the aerial parts of the resulting plants were normally glanded. Mortality rates of germinating seed and young plantlets were very high (76%) for BC1 material but decreased markedly in following generations. Cytogenetic observations confirmed the soundness of the introgression strategy. Both tri-species hybrids and several BC1 and BC2 genotypes issued from nearly totally glandless seeds were fertile and showed high frequencies of multivalent and chiasma formations at metaphase I, indicating important genetic material exchanges.