Differential dependence of apple (Malus domestica Borkh.) cultivars on the xanthophyll cycle for photoprotection

Abstract

The dependence of fruit peel photosystems of ‘Granny Smith’, ‘Braeburn’, ‘Fuji’, ‘Golden Delicious’ and ‘Topred’ apple (Malus domestica Borkh.) peel on the xanthophyll cycle for photoprotection was studied under laboratory conditions. Mature fruit peel was either treated with 1 mm dithiothreitol (DTT) to inhibit the xanthophyll cycle or not treated. Fruit peel was subsequently exposed to photosynthetic active radiation stress of 1 500 µmol m⁻² s⁻¹ combined with heat stress of 45 °C for 3 h. Fruit peel photodamage was assessed by measuring the change in the maximum light use efficiency of photosystem II (Fv/Fm). The change in the concentration of the xanthophyll-cycle carotenoids zeaxanthin, antheraxanthin and violaxanthin plus lutein and β-carotene were analysed. The Fv/F_m of heat- and light-stressed DTT-treated (+DTT) ‘Granny Smith’ and ‘Braeburn’ peel had a low recovery after stress compared with the recovery Fv/F_m of similarly stressed peel not treated with DTT (−DTT). However, there was no difference in the recovery F_v/Fm between +DTT and −DTT ‘Fuji’, ‘Golden Delicious’ and ‘Topred’ peel. The photosystem of ‘Granny Smith’ and ‘Braeburn’ fruit therefore appear to have a higher dependency on the xanthophyll cycle for photoprotection than ‘Fuji’, ‘Golden Delicious’ and ‘Topred’ fruit.