HISTOLOGICAL STUDY OF CALLUS AND SOMATIC EMBRYOGENESIS OF MANDARIN CULTIVARS (Citrus reticulata)

Citrus fruits are one of the most dominant horticultural fruit crops in the world. The development of an efficient regeneration system is crucial for the genetic transformation of citrus species. This study aims to develop an effective protocol for the induction of embryogenic callus and the regeneration of seven varieties of mandarin and to proceed to an Histologic analysis of embryogenic and non-embryogenic callus to ensure the effectiveness of callus regeneration capacity. For all cultivars, the best results for embryogenic callus induction were obtained with Nadorcot variety on culture medium containing both media Ms (2 mg/l AIA + 1 mg/l kinetin and Ms/2 + 1 mg/l Kinetine, whereas a total absence of embryo development was observed in the different tested media. The combinations Auxin-Auxin, Auxin-cytokinin, and Auxin-amino acid, with a concentration of 2.4 d 1 mg/L constant to verify the effective response of excised embryos to callus induction and regeneration. It was observed that the MT medium containing 1 mg/l of 2.4-D and 0.5 mg/l of BAP yielded the best results (67%) for the development of callus, whereas the media containing combination of Auxin-amino acid and Auxin-cytokinin favoured the development of an indirect organogenesis.