Enhancement of Chilling Stress Tolerance of Tomato Fruit by Postharvest Brassinolide Treatment

Tomatoes, originally a tropical fruit, cannot easily be stored at low temperatures, due to the risk of chilling injury (CI). To develop an effective technique to reduce CI, the effects of treatment with 0, 3, and 6 mu M brassinolide (BR) on chilling injury, electrolyte leakage (EL), contents of malondialdehyde (MDA) and proline, and activities of phospholipase D (PLD) and lipoxygenase (LOX) were investigated in tomato fruit stored at 1 A degrees C for 21 days. Treatment with BR, especially at 6 mu M, significantly alleviated chilling injury, reduced EL and MDA content, and increased proline content. Also, fruit treated with BR exhibited significantly lower PLD and LOX activities as compared with the control fruit. These results suggest that PLD and LOX are associated with the induction of CI in tomato fruit. BR might reduce CI by inhibiting PLD and LOX activities and by enhancing membrane integrity.