In vitro plant regeneration from mature tissues of Thomson navel sweet orange (Citrus sinensis L. Osbeck.)

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 Bs 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 GA(3). 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.