Factors affecting morphogenesis from immature cotyledons of Phaseolus coccineus L.

Direct somatic embryogenesis as well as somatic embryogenesis and organogenesis mediated by small glossy calluses were obtained from immature cotyledon explants of bean (P. coccineus) cv Streamline 770 on a modified half-strength MS medium (Murashige & Skoog 1962) containing various concentrations of (2-isopentenyl)adenine and 2-naphthoxyacetic acid. Substitution of sucrose with glucose gave, in the range of concentrations tested, the strongest enhancement of the morphogenic process. Further improvement regarding the number of morphogenic cotyledons, the number of regenerations per cotyledon and the quality of the embryos was observed when 2,3,5-triiodobenzoic acid or abscisic acid were added to the medium. After cycles of micropropagation on MS medium plus 4.4 M 6-benzyladenine and rooting in the absence of growth factors, plantlets were adapted to ex vitro conditions and grown to maturity.Abbreviations ABA abscisic acid - AC activated charcoal - BA 6-benzyladenine - 2,4-D (2,4-dichlorophenoxy)acetic acid - DHZ dl-dihydrozeatin - IAA indole-3-acetic acid - 2iP (2-isopentenyl)-adenine - NAA 1-naphthaleneacetic acid - NOA 2-naphthoxyacetic acid - PBA N-benzyl-9-(2-tetrahydropyranyl)adenine - PIC picloram - PVP polyvinylpyrrolidone - TDZ thidiazuron - TIBA 2,3,5-triiodobenzoic acid - ZEA zeatin