Growth regulators, culture media and antibiotics in the in vitro shoot regeneration from mature tissue of citrus cultivars

The objective of this study was to evaluate the effects of 6-benzylaminopurine (BAP) and a-naphthaleneacetic acid (NAA) combinations, basal media and beta-lactam antibiotics on in vitro organogenesis from mature stem segments of 'Pera', 'Valencia' and 'Bahia' sweet oranges and 'Cravo' rangpur lime. For induction of shoot regeneration, the segments of the four cultivars were placed on Murashige and Skoog (MS) medium containing the following BAP/NAA concentrations: 0.0/0.0; 0.25/0.0; 0.25/0.25; 0.5/0.0; 0.5/0.5; 1.0/0.0; 2.0/0.0; 2.0/0.25; 2.0/0.5; and 2.0/1.0 mg L(-1). In order to test the influence of the culture media on shoot-bud induction, (MS), Murashige and Tucker (MT), and woody plant medium (WPM) formulations were evaluated, associated with the best combination of plant growth regulators obtained in the previous experiment. The influence of four beta-lactam antibiotics (timentin, cefotaxime sodium salt, meropenem trihydrate and augmentin) on shoot regeneration was determined. Better regeneration responses were achieved when internodal segments were cultured onto MS-based medium with 500 mg L(-1) cefotaxime with the following BAP/NAA concentrations: 0.5 + 0.25 mg L(-1) for 'Cravo', 1.0 + 0.25 mg L(-1) for 'Valencia' and 'Bahia', and 1.0 + 0.5 mg L(-1) for 'Pera'. Genotype, growth regulators, basal media and beta-lactam antibiotics affect the morphogenetic response in mature tissues of citrus.