Factors affecting in vitro adventitious shoot formation on internode explants of Citrus aurantium L. cv. Brazilian

The in vitro formation of newly formed adventitious buds and shoots from internodal branch segments was studied on 12-month-old plants of Citrus aurantium L. cv. Brazilian. The effects of 6-Benzyladenine (BA) and α-Naphthalene acetic acid (NAA) treatments were evaluated on adventitious bud and shoot regeneration. High rates of bud initiation and shoot development were obtained both with BA supplemented medium, in the range from 1 mg L−1 to 3 mg L−1, and with 0.1 mg L−1 NAA supplemented medium. NAA concentrations above 1 mg L−1 significantly reduced bud initiation and shoot elongation. The results obtained using different in vitro culture vessels such as Petri dishes, tubes and glass culture jars were compared. The highest adventitious bud induction was observed in Petri dishes for internodes cultured in 2 mg L−1 BA supplemented medium, with 95% responsive explants forming 9.0 ± 2.4 adventitious buds. The adventitious buds observed in Petri dishes reached a maximum height of 1 mm, with no further development, while some of the adventitious shoots cultured in tubes and glass culture jars grew over 1 cm in height. A shoot regeneration gradient of the internodes collected along the branch axis was noticed, with basal ones exhibiting higher regeneration frequency.

► Internode explants from 12-month-old plants have a high regeneration efficiency.
► BA alone promotes high values of bud initiation and shoot development.
► Type of culture containers promotes distinct response on bud and shoot neoformation.
► The neoformation potential of the internodes along the branch axis is distinct.
► Basal internodes on the branch have higher regeneration frequency than apical ones.