Induction of Highly Embryogenic Calli and Plant Regeneration in Upland ( L.) and Pima ( L.) Cottons

摘要

To accomplish our objective of broadening the number of regenerable cotton lines, we developed a protocol capable of producing plants through somatic embryogenesis of diverse cotton species. Callus was initiated from hypocotyl and cotyledon explants on a callus initiation medium [CIM; modified MS with 1 mg La?’1 kinetin and 2 mg La?’1 naphthaleneacetic acid (NAA)]. Friable embryogenic callus was periodically selected and transferred onto callus selection/maintenance medium (CS/MM) [modified MS with 0.1 mg La?’1 kinetin and 0.5 mg La?’1 NAA]. The selected callus was then transferred into a liquid embryo initiation medium (EIM) (modified MS medium in which NH4NO3 was removed and KNO3 amount doubled) followed by transfer to solid embryo maturation media EMMS2 (0.5 mg La?’1 NAA + 0.05 mg La?’1 kinetin). The liquid step not only decreased the culturing time but also increased the number of embryos per gram of cultured tissue. Germinating somatic embryos were placed on MS medium with no hormones and plantlets were acclimatized before transfer to the greenhouse. Significant numbers of somatic embryos and their derived plantlets were obtained from a commercial cultivar of G. hirsutum, Deltapine 90 and G. barbadense accession GB-35B126 (PI-528306). The mean embryos per gram for Deltapine 90 on EMMS2 were higher than those previously reported for Coker 312. Highly significant differences were found between the two genotypes for both embryo and plant production. To our knowledge, this is the first report of regeneration of G. barbadense through somatic embryogenesis.