Rootstocks used for historical citrus cultivated in pots - in vitro propagation

Several experiments were carried out to develop protocols for in vitro propagation of citrus rootstocks using shoot-tip explants from seedlings. At the beginning Murashige & Skoog (MS) medium was supplemented with different concentrations of kinetin (6-furfurylaminopurine), later nutrient medium consisting of Driver and Kinyuki salt formula (DKW) and Kinetin was used amended with BAP (6-benzylaminopurine). These tests were performed with explants of sour orange (Citrus aurantium L.), Alemow (Citrus macrophylla Wester), Volkameriana (Citrus volkameriana Ten. et. Pasq.) and Poncirus (Poncirus trifoliata (L.) Raf). In other experiments, explants of Citrumelo (Citroncirus citrumelo, C. paradisi × P. trifoliata Raf.) and Citrange (Citrange troyer, hybrid between C. sinensis Osbeck and P. trifoliata Raf.) were cultured on MS mineral elements and then were tested on DKW medium with different concentrations of BAP, GA₃ (gibberellic acid) and IBA (3-indolbutyric acid). The highest number of axillary shoots per explant was obtained on DKW medium supplemented with only BAP at concentration of 0.8 mg L^‑1 (Poncirus), 1.0 mg L^‑1 (Citrange), 0.6 mg L^‑1 (Citrumelo). At the end of three subcultures shoot multiplication rate was 1:8.94 Poncirus, 1:6.44 Citromelo and 1:5.83 Citrange. Different concentrations of IBA (3-indolbutyric acid) and NAA (1-naphtylacetic acid) were tested for in vitro root induction obtaining different responses, scarce rooting for Poncirus (68% of shoots developed roots on medium with NAA) and good results for Citromelo and Citrange (100% of shoots developed roots on peat/perlite substrate wetted with MS formula solution and added with IBA).