Foliar application of algal biostimulant improves the quality of peach fruits

To improve the quality of peach fruits, foliar sprays of algal biostimulant at different concentrations (600-, 900-, 1200- and 1500-fold dilutions) were applied to peach trees, aiming to investigate the effects of the biostimulant on peach fruit quality. The 900- and 1200-fold dilutions of algal biostimulant resulted in increases in single fruit weight, fruit transverse diameter, total soluble solid content, vitamin C content and solid:acid ratio to some extent. Furthermore, only the 1200- and 1500-fold dilutions of algal biostimulant led to an increase in fruit firmness. The 900-fold dilution of algal biostimulant produced the highest levels of total soluble solids and vitamin C, with a 49.42% and 46.12% increase compared with control. Additionally, the 900- and 1200-fold dilutions of algal biostimulant decreased the titratable acid content by 15.72% and 20.13%, respectively, compared with control. Algal biostimulant also raised sugar content and the activities of lipoxygenase, ascorbate peroxidase, and phenylalanine ammonia lyase to some extent, while lowering the activity of polyphenol oxidase. Moreover, the strong relationship between fruit shape index, titratable acid content, polyphenol oxidase activity and hardness, while other parameters showed close associations. In conclusion, algal biostimulant can improve the quality of peach fruits, with the 900-fold dilution being the most effective concentration. Significance of the study What is already known on this subject? Algal biostimulants are rich in macroelements and trace elements and also contain auxin, cytokinin and other substances that can stimulate plant growth and improve the quality of fruits. However, few studies have investigated their impact on stone fruit trees. What are the new findings? This study shows that algal biostimulant can improve the quality of peach fruits, with the 900-fold dilution being the most effective concentration. What are the expected impacts on horticulture? Adopting appropriate measures can enhance the quality of fruits. This study provides the optimal algal biostimulant concentration that can effectively enhance the quality of peach fruits, serving as a valuable resource for producing high-quality peaches.