The isolation, culture and division of protoplasts from citrus cotyledons

High yields (2.3 × 10⁵ to 1.3 × 10⁶ protoplasts/g.f.wt.) of isolated protoplasts were obtained from cotyledons of Cirus sinensis (L.) Osb. 'Valencia'. Osmotic potential of the medium and enzyme concentrations were important in obtaining high viability of preparations as indicated by FDA fluorescence. Adding malt extract to a Murashige-Tucker basal medium increased plating efficiencies somewhat, but not the rate or duration of cell division. However, modifying the NAA and kinetin concentration optimized plating efficiencies (up to 20%) of protoplasts and also the rate or duration of cell division. The highest plating efficiency and number of cells per colony were obtained on a defined medium containing NAA (15 μ M ). and kinetin (4.6 μ M ). Coincidence of percentage protoplast viability after 13 days (assessed by FDA fluorescence) with plating efficiency after 21 days indicates that FDA fluorescence is an accurate indicator of citrus protoplast viability.