Hot air treatment induces resistance against blue mold decay caused by Penicillium expansum in sweet cherry (Prunus cerasus L.) fruit

- Hot air treatment efficiently inhibited blue mold rot caused by Penicillium expansum in sweet cherry fruit.
- Hot air treatment significantly induced defense-related enzymes in sweet cherry fruit.
- Hot air treatment remarkably up-regulated the expression of defensive genes.
- Hot air treatment effectively inhibited activities of polygalacturonase and pectinmethylesterase.

Effect of hot air (HA) treatment (44 °C, 114 min) on reducing blue mold decay caused by Penicillium expansum in sweet cherry fruit was investigated. The results indicated that fruit treated with HA had significantly lower disease incidence and smaller lesion diameter than the control fruit did. HA treatment significantly enhanced activities of chitinase (CHI) and β-1, 3-glucanase (GLU). The activities of polygalacturonase (PG) and pectinmethylesterase (PME) were significantly inhibited by HA treatment. Fruit treated with HA exhibited remarkably higher activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and polyphenoloxidase (PPO) and lower activity of ascorbate peroxidase (APX) than control. Expression of defense related genes such as PaGLU, PaCAT, and PaNPR1-like was greatly induced in HA-treated fruit during storage, while the expression of expansins (EXP) was down-regulated by HA treatment. These results suggest that HA can effectively inhibit blue mold decay caused by P. expansum in harvested cherry fruit possibly by directly inducing disease resistance and delaying fruit tissue softening that helps to ward off the spread of pathogens.