CALLUS INDUCTION FROM IN VITRO LEAVES OF JUGLANS REGIA 'LVBO'

In vitro leaves of ‘Lvbo’ walnut (Juglans regia L.) were used as explants. The effects of culture in the dark and the types and ratio of plant growth regulators (PGRs) on callus induction were studied. The results were as follows. There was a significant influence of dark incubation time on leaf callus formation. After 2 weeks of dark treatment the rate of leaf calling could be up to 100%. Increase in dark incubation time inhibited the formation of leaf callus. Low concentration of TDZ (2.0 to 4.0 mg/L) promoted the formation of leaf callus but high concentrations (8.0 to 10.0 mg/L) inhibited the formation and browning of leaf callus and made the structure of the callus more porous. In addition, formation of callus was promoted by 2,4-D, IBA and NAA, but the dose responses were different. Low concentration of 2,4-D (1.0 mg/L) promoted the formation of leaf callus, but high 2,4-D (2.0 mg/L) was inhibitory. Low concentration of IBA (0.01 to 0.5 mg/L) were conducive to leaf callus formation but a higher amount (1.0 mg/L) resulted in poor leaf callus formation. NAA (0.1 to 0.5 mg/L) in the range of concentrations tested also promoted the formation of callus.