Foliar application of sucrose and Bordeaux mixture enhances freezing tolerance in radish (Raphanus sativus L.)

Although radish is considered a cool-season vegetable, freezing temperatures can cause serious problems for its growth. To enhance radish tolerance to freezing stress, an experiment was conducted in a completely randomized factorial design. This design incorporated two factors: sucrose concentration (zero and 0.5%) and anti-stress compounds (control, 1 mM salicylic acid, 0.1 mM sodium nitroprusside (SNP), and 0.5% Bordeaux mixture), with four replications for each treatment. The findings indicated that plants sprayed with a combination of sucrose and Bordeaux mixture exhibited the highest storage hypocotyl flavonoid content (0.125 µg Quercetin/mg extract). This value was not significantly different from that observed in plants treated with SNP alone or with sucrose alone (without any antistress compounds). lants treated with Bordeaux mixture alone (without sucrose) showed a higher membrane stability index (94.33%), which was significantly different only from the control and salicylic acid treatments. Plants treated with Bordeaux mixture + sucrose- showed the lowest storage hypocotyl lipid peroxidation and the highest chlorophyll b content (0.928 mg/g FW) and total chlorophyll (2.976 mg/g FW) in the leaves. The highest hypocotyl lipid peroxidation was observed in control plants and in plants treated with salicylic acid alone. Control plants (no sucrose or anti-stress compounds) and plants treated with salicylic acid displayed the highest storage hypocotyl proline content. There was a significant negative correlation between leaf proline and storage hypocotyl lipid peroxidation (r=-0.85) and storage hypocotyl flavonoid and lipid peroxidation (r=-0.74). In addition, we found a significant negative correlation between leaf membrane stability percentage and storage hypocotyl lipid peroxidation (r=-0.79). In conclusion, this study demonstrates that most of the compounds tested could enhance the storage hypocotyl’s tolerance to freezing stress. However, the combination of sucrose and Bordeaux mixture proved to be the most effective and warrants further investigation in future research.