Dark preconditioning, CPPU, and thidiazuron promote shoot organogenesis on seedling node explants of common and faba beans
1992
Mohamed, M.F. | Read, P.E. | Coyne, D.P.
Dry seeds from two lines of common bean (Phaseolus vulgaris L.) and one cultivar of faba bean (Vicia faba L.) were germinated on Murashige and Skoog (MS) medium containing B5 vitamins, 30 g sucrose/liter, and either 2.5, 5.0, or 7.5 micrometers benzyladenine (BA). Axenic seed cultures were grown at 22 to 24C in darkness and under continuous light from cool-white fluorescent tubes (40 micromoles.m-2.s-1). Explant tissues were prepared from cotyledonary nodes (CN) and primary nodes (PN) of 14-day-old seedlings. Explants were cultured on corresponding seedling growth medium and maintained under continuous cool-white light (40 micromoles.m-2.s-1). The percentages of CN and PN (in one line of common bean) explants that regenerated shoots and the number of shoots per explant (in all germplasm) were highest when nodal tissues were prepared from seedlings germinated in darkness. These responses were optimal on medium containing 5 micrometers BA during seedling growth and subsequent culture of explants. The number of shoots per explant was two to five times higher on explants cultured on medium with 0.25 to 1.0 micrometers forchlorfenuron (CPPU) or thidiazuron (TDZ) than on medium with 5 micrometers BA. Higher (2.5 and 5 micrometers) CPPU and TDZ concentrations inhibited shoot elongation and stimulated callus production. Histological analyses indicated that adventitious meristems formed 6 to 8 days after explant culture. Progenies from regenerated plants appeared similar to plants raised from the original seed stocks.
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