Investigation of responses of some apple (Mallus x domestica Borkh.) cultivars grafted on MM106 and M9 rootstocks to lime-induced chlorosis and oxidative stress

- Physiological and biochemical responses of apple cultivars and rootstocks showed great variations under lime induced iron chlorosis condition.
- Iron deficiency stress reduced active Fe, total Fe, chlorophyll and FCR activity while increased the MDA, H2O2, SOD and APX activity of cultivars and rootstocks.
- Suitable cultivar-rootstock combinations is a good strategy to overcome Fe chlorosis in apple plants grown in calcareous soils.

The response of dwarf (M9) and semi dwarf (MM106) clonal apple rootstocks and 5 apple cultivars [Granny Smith (GS), Fuji (F), Royal Gala (RG), Mondial Gala (MG) and Red Chief (RC)] grafted on these rootstocks to lime induced iron chlorosis and iron deficiency induced oxidative stress were investigated. Both rootstocks and cultivars were divided into two groups. One of the group were kept as control group. To the second group, to ensure the lime-induced chlorosis, bicarbonate (HCO3−) was applied. Both groups were grown for two years in a pot experiment. The soil used in the experiment was a clay loam calcareous soil containing 70.9 g kg−1 lime. To evaluate the lime-induced chlorosis effects on both rootstocks and cultivars, accumulation of H2O2 and membrane damage (MDA, lipid peroxidation), activities of catalase (CAT, EC 1.11.1.6), superoxide dismutase (SOD, EC 1.15.1.1) and ascorbate peroxidase (APX, EC 1.11.1.11) determined. Bicarbonate treatment reduced active and total Fe and total chlorophyll concentrations, and FCR (leaf ferric chelate reductase) activity while increased the MDA, H2O2, SOD and APX activity of cultivars and rootstocks in both years. These changes and the statistical significances of individual and combined effects of treatment and cultivar or rootstocks showed great differences among the cultivars and rootstocks. So B/C rates helped us to evaluate the tolerance to lime induced chlorosis of the cultivars and rootstocks. B/C referring Fe efficiency ratio calculated as the value for the bicarbonate treatment divided by that for the control for each parameter studied used for tolerance state of cultivars and rootstocks. According to B/C ratios calculated for active and total Fe, FCR, the MG and RG grafted on both rootstocks regarded as tolerant cultivars. In addition to this, the MM106 rootstock was more tolerant than the M9 rootstock under bicarbonate applied condition giving higher B/C ratio for active and total Fe, total chlorophyll, FCR and APX but lower MDA concentrations. It can be concluded that suitable cultivar-rootstock combinations is a good strategy to overcome Fe chlorosis in apple plants grown in calcareous soils.