Figure 2.

PCR identification of MdcyMDH‐overexpressing apple plants and the evaluation of salt and cold tolerance of transgenic plants. (a) PCR identification using DNA templates and the specific primers from 35S and MdcyMDH. (b) MdcyMDH expression in the leaves of wild‐type (WT) and transgenic lines. (c–e) WT and transgenic apple in vitro shoot cultures at 20 days after a subculture were taken as the control (c); the cultures with the same subculture conditions as the control were subjected to stress treatments, that is at 50‐mm NaCl for 10 days and subsequent 100‐mm NaCl for 9 days (d); at 8 °C for 7 days and subsequent 0 °C for 7 days in a 14‐h light photoperiod (e). (f, g) Shoots and leaves of the 3‐year‐old pot‐cultured WT and transgenic apple trees prior to stress treatments (f) and after 100‐mm NaCl for 14 days and subsequent 150‐mm NaCl for 7 days (g). (h, i) Contents of chlorophyll (a + b) of the leaves from the transgenic apple cultures (h) and trees (i) under normal and stress conditions. Values represent the means ± SD of three replicates. M, DNA marker; NC, negative control (H₂O); PC, positive control (plasmid DNA of 35S::MdcyMDH). **Highly significant difference, P < 0.01.