Transformation and characterization of TfGA2-ox2 gene in cell suspension cultures of 'Bingtangcheng' sweet orange (Citrus sinensis L. Osbeck)

Gibberellins (GAs) are endogenous hormones that play a predominant role in regulating plant stature. In this work, TfGA2-ox2 gene was introduced into callus lines of 'Bingtangcheng' Sweet orange (Citrus sinensis L. Osbeck) by Agrobacteriummediated transformation with the aim of decreasing the amounts of bioactive GA in these plants and thereby reducing their stature. To optimize the transformation conditions, several factors were assessed, including co-cultivation period, duration of pre-culture in darkness and the infection time of Agrobacterium tumefaciens. PCR analysis confirmed the successful integration of TfGA2-ox2 gene in kanamycinresistant calluses. The average percentage of kanamycin-resistant calli on selection medium containing MT basal medium supplemented with kanamycin (50 mg/L) and cefotaxime (400 mg/L) was 11.71%. Maximum transformation percentage of resistant callus lines based on polymerase chain reaction detection was 69.23%. The resistant callus lines will be used for quantification of GA concentrations and are now subject to plantlet regeneration. This approach may provide an alternative to the application of chemical growth retardants used for reducing the stature of plants.