In vitro Callus Induction of Tomato and Evaluation of Antioxidant Activity of Aqueous Extracts and Enzymatic Activities in Callus Cultures

Background: Tomato (Solanum lycopersicum L.) is an important plant rich in many vitamins and antioxidant enzymes. Methods: Tomato leaves of two cultivars (‘Peto 86’ and ‘Strain B’) were used as explant sources for callus induction. The antioxidant activity of the calli ethanol (ET) and methanol (ME)extracts were determined. The enzymatic activities were evaluated in callus cultures. Callus induced from leaf explants of tomato cultivars on the Murashige and Skoog (MS) medium supplemented with various concentrations and combinations of cytokinins and auxins such as BAP (6-benzylaminopurine), NAA (1-naphthalene acetic acid), 2,4-D (2,4-dichlorophenoxyacetic acid), IAA (indole-3-acetic acid) and Kin (Kinetin) for rapid induction of callus and biomass growth. Results: The medium (M2) containing 3 mg L-1 BAP with 1 mg L-1 IAA produced the highest percentage of callus induction (PCI) (100%) in two cultivars. The relative fresh weight growth (RFWG) was reported by the fresh callus weighed after four weeks of culture and again weighed after one month of sub-culture. In both cultivars cultured on M2 medium the RFWG was (1.60) in ‘Peto 86’ and (1.47) in ‘Strain B’. The results showed that PCI and RFWG differed with the cultivars tested. The scavenging DPPH free radical activity in callus (ET) extracts exhibited a significant increase in (P < 0.05) than the activity in callus (ME) extract. The peroxidase and polyphenol oxidase activities were found in calli of both tomato cultivars. The enzymatic activities were higher in callus of ‘Peto 86’ cultivar than in callus of ‘Strain B’ cultivar. Conclusions: Calli had antioxidant and enzyme activities that can be beneficial for extracting important components or for plant regeneration.