Effect of X-ray irradiation on nutritional and antifungal bioactive compounds of 'Clemenules' clementine mandarins

Abstract

X-ray irradiation (510 and 875 Gy) of intact unwounded 'Clemenules' mandarins increased the rind biosynthesis of the phytoalexins scoparone and scopoletin after storage at 20 degrees C for up to 14 d, but not at 5 degrees C for up to 60 d. In general, irradiation did not affect the content of polymethoxyflavones in the rind and vitamin C and flavanone glycosides in the juice. Clementines that were wounded, irradiated at 510 Gy and inoculated with Penicillium digitatum, contained higher scoparone and scopoletin levels than non-irradiated ones. Sodium carbonate treatment (3% SC) increased scoparone but not scopoletin levels in inoculated fruit. SC treatment and irradiation at 510 Gy induced highest scoparone and scopoletin accumulation 3d post-fungal inoculation at 20 degrees C (125.3 and 15.4 mu/g rind dry weight, respectively), and effectively inhibited green mold. However, phytoalexin levels declined and disease control failed 5 d after fungal inoculation. Irradiation at 875 Gy appeared to be phytotoxic and did not induce phytoalexin production nor prevented green mold in rind wounds. (C) 2012 Elsevier B.V. All rights reserved.