The objective of this work was to obtain autotetraploid plants of 'Murcott' tangor, 'Ponkan' mandarin and 'Pêra-de-abril' sweet orange to be used in crosses with diploid cultivars, aiming to produce triploid seedless hybrids. The methodology used was the in vitro culture of epicotyl segments in media containing different concentrations of colchicine (0.025, 0.05 and 0.1%), for several periods of time (1, 2, 3, 7 and 14 days), followed by the regeneration of adventitious shoots in culture media without the alkaloid. All shoots obtained were micro-grafted, acclimatized and transferred to a greenhouse. The evaluation of the ploidy level of the plants was performed by flow citometry technique. Colchicine was toxic to the explants of three varieties, and caused the reduction on the average number of shoots regenerated per explant as well as an increase in the percentage of non-responsive explants when comparing with the control plants. Among four plants of sweet orange obtained, two of them showed to be autotetraploid. The only plant of tangor obtained also showed to be autotetraploid. These plants presented thicker and roundisher leaves displaying deeper green color. The methodology used resulted efficient for obtaining tetraploid plants.
Citrus; tetraploid; epicotyl; in vitro regeneration; tissue culture
