Nitrogen foliar treatments as a tool to improve in vitro shoot regeneration in olive

An investigation to evaluate the effects of foliar treatments of different concentrations of urea (0.00 control, 0.20, 0.29, 0.58, 0.84, and 1.16 gL-1) on the in vitro multiplication of explants of olive was conducted in 2020. Uninodal explants of the cultivar Frantoio in olive medium (OM) enriched with 4 mgL-1 of zeatin, 30 gL-1 of sucrose, and 7 gL-1 of agar were used. The results indicated that preculture immersion soaking of the explants in solutions of urea at the concentrations of 0.29 to 0.58 gL-1 improved growth parameters, thus producing longer shoots with a higher number of nodes compared with the control, resulting in a higher multiplication rate. This was associated with an increase in the biomass/node, which should produce greater vigor and, thus, high regeneration if the shoots will be used for subsequent proliferation cultures or greater rooting if used to complete the micropropagation process.