Abstract. In order to optimize a reliable method for plantlet regeneration from mature tissues of Thomson Navel citrus (Citrus
sinensis Osbeck. Cv. Thomson), four basal media, different explants and cutting modes were assessed. Furthermore a wide range of
phytohormones were studied comprehensively for optimum shoot induction, elongation and rooting of the shoots. Results showed
that while MS and MT (Murashige and Tucker) basal media were statistically similar, they were superior to WPM (woody plant
medium) and B5 media in terms of response promptness and shooting efficiency. The two cut modes were not significantly different
and internodal segments, cut either longitudinally or transversely, produced more adventitious shoots (average of 2 and 2.1 shoots
per explant) compared to shoot tip explants (1.1). The highest explant response was observed in media supplemented with 3 mg L-1
BA and 0.1 or 0.5 mg L-1 NAA (72 % responsive explants) but the highest shooting efficiency, with an average of 3.2 shoots per
explant, was achieved when 1 mg L-1 BA and 0.1 mg L-1 NAA were applied. Results also revealed that the best elongation records
were established in media fortified with 0.5 mg L-1 BA and 0.1 mg L-1 GA3. To the best of our knowledge, this is the first report on in
vitro plant regeneration from mature tissues of grove-grown citrus. The findings of this study could be used for micropropagation of
healthy seedlings without a juvenile phase accelerating fruiting of citrus groves.