Lycopene Content of Hydroponically Cultivated and Grafted Tomato Varieties

Freeze-dried tomato powder (100 mg) was extracted by 1 mL hexane/acetone/ethanol (2:1:1, v/v/v) under shaking for 30 min at room temperature, after which 0.2 mL ddH2O was added and vigorously mixed. The polar and non-polar phases were separated by centrifugation at 3000 xg for 10 min, after which the non-polar phase containing lycopene was collected. The remaining plant material was extracted once more using 1 mL hexane/acetone/ethanol (2:1:1, v/v/v) as described above.

The content of lycopene was determined by measuring the absorbance spectrophotometrically at 503 nm (εlycopene =1.72 × 105 M-1cm-1). Comparing self-grafted Big Beef, Black Krim, and Green Zebra showed lycopene contents of 9.97±2.02, 15.55±1.97, and 3.37±0.39 mg/kg dry weight (mean±std), respectively. The results were statistically significantly different between the three varieties reflecting the natural pigmentation in each.

When comparing the effect of grafting onto non-WT rootstocks, surprisingly, Big Beef grafted onto Supernatural demonstrated significantly higher lycopene content (17.25±0.24 mg/kg dry weight) compared to both WT (9.97±2.02 mg/kg dry weight) and Arnold (8.09±1.39 mg/kg dry weight) rootstocks. Similar effects were not observed for the grafted heirloom varieties, for which the lycopene content was determined to be 15.55±1.97, 16.29±2.93, 19.14±3.21 mg/kg dry weight for Black Krim grafted onto WT, Arnold, and Supernatural, respectively, and 3.37±0.39, 3.52±0.15, 3.03±0.03 mg/kg dry weight for Green Zebra grafted onto WT, Arnold, and Supernatural, respectively.