Autotetraploid tangor plant regeneration from in vitro Citrus somatic embryogenic callus treated with colchicine

In vitro chromosome doubling of embryogenic callus lines of the Citrus cultivars `Umatilla' and `Dweet' tangors (Citrus reticulata BlancoxC. sinensis [L.] Osb.), `Caffin' clementine (C. clementina Hort. ex Tan.) and `Wheeny' grapefruit (C. paradisi Macf) was carried out in the presence of either 0.05 or 0.1% colchicine, or 0.01, 0.05 or 0.1% oryzalin. Embryogenic callus development was partly suppressed in the presence of colchicine, and completely suppressed by oryzalin at all concentrations tested. No plants were regenerated from any of the oryzalin treatments. Ploidy level of plants regenerated from the colchicine treatments was determined using flow cytometry and chromosome squashes. Three desirable non-chimeric, autotetraploid plants of the mono-embryonic cultivar `Umatilla' were produced using 0.05% colchicine and one from 0.1% colchicine. One mixoploid `Dweet' plant was produced using 0.1% colchicine.