RESUMO
We analyzed the best light intensity for callus induction and maintenance in Vitis vinifera and explored the mechanism of grape callus browning. Tender stem segments of grape cultivar "gold finger" were used to study the effects of different light intensities (0, 500, 1 000, 1 500, 2 000, 2 500, 3 000 and 4 000 Lx) on the induction rate, browning rate and associated enzyme activity and gene expression during Vitis vinifera callus formation. The callus induction rate under 0, 500, 1 000 and 1 500 Lx was more than 92%, significantly higher than in other treatments (P < 0.05). A lower browning rate and better callus growth were also observed during subculture under 1 000 and 1 500 Lx treatments. We found that chlorogenic acid, caffeic acid, p-hydroxybenzoic acid and coumaric acid contents were correlated with the browning rate of callus, among which chlorogenic acid content was positively correlated with the browning rate (P < 0.05). Peroxidase (POD) and polyphenol oxidase (PPO) activities were negatively correlated with the browning rate of callus (P < 0.01). The POD, PPO and phenylalanine ammonialyase (PAL) expression levels were positively correlated with the browning rate at P < 0.05 or P < 0.01. An appropriate light intensity for the tissue culture of Vitis vinifera was 1 000-1 500 Lx, higher or lower light intensities significantly impaired normal callus growth.