In Vitro Regeneration of Tomato (Lycopersicon esculentum) Plants under Drought Stress
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This experiment was conducted to regenerate tomato plants in the presence of polyethylene glycol (PEG). Calli were induced from cotyledonal leaf, shoot tip, stem, and leaf of two tomato cultivars on MS medium supplemented with 1 mg /L BA and 0.6 mg /L IBA. The produced calli were subjected to drought stress on MS media supplemented with 0, 20, 40, 60 gm /L PEG. The results showed no significant differences between the two cultivars in the calli fresh weights of the different explants. However, there were differences among the explants. Stem callus showed the highest followed by the leaves. Also Super Regina’s stems showed significantly higher callus fresh weight than Falcon’s stems. Leaf’s and stem’s calli dry weights were equal and they were significantly different from the cotyledonal leaves and the shoot tips. Callus fresh and dry weights of both cultivars were reduced as PEG increased. The highest callus fresh weight was for Super Regina in 0 g/L PEG and the lowest was for Falcon in 60 g/L PEG. At 20 g/L PEG, Falcon callus fresh weight was significantly higher than Super Regina. In all PEG treatments Falcon’s callus dry weight was significantly higher than Super Regina’s except at 40 g/L PEG they were equal. Plant regeneration in the presence of PEG from both cultivars was severely affected. The number of regenerated plants was reduced on 60 g/L PEG, whereas 0 g/L PEG and 40 g/L PEG showed the highest number of regenerated plant/explant.
Keywords: Tomato, PEG, Drought, Tissue culture