X-rays irradiation affects flavonoid synthesis and delays reddening of winter jujube (Zizyphus jujuba Mill. cv. Dalidongzao) during cold storage

This study investigated the color and pigment content changes, the activities of flavonoid biosynthesis related enzymes and relative expression of genes of irradiated winter jujubes during cold storage at 0 ± 1 ℃ for 70 d. The results showed that 0.3 kGy X-rays could maintain the lightness and superior appearance of winter jujube while suppressing the decay. In addition, the activities of phenylalanine ammonia-lyase (PAL) and dihydroflavonol reductase (DFR) were restricted in 0.3 kGy X-rays treated jujubes, and the relative expression of MYB transcription factors (LOC107415776 and LOC107404478) and bHLH transcription factors (LOC107407443, LOC107423582 and LOC107423649) were down-regulated, causing the reduced anthocyanin and quercetin content. Together with the alleviated chlorophyll degradation levels delayed the reddening of irradiated jujube. This research demonstrates the potential of 0.3 kGy X-rays in delaying winter jujube reddening, which can provide a solid theoretical reference for the mechanism study. • X-ray is a promising non-thermal preservation technology. • 0.3 kGy X-rays delay the reddening of winter jujube. • 0.3 kGy X-rays inhibit anthocyanins and quercetin synthesis. • 0.3 kGy X-rays reduce PAL and DFR activities. • 0.3 kGy X-rays restrict relative expression of MYB and bHLH.