Effect of variety and seaweed extract spray in the content of some medically active phenolic compounds in grape fruits

Grape (Vitis vinifera L.) is one of the most economically significant fruit crops which has a large adaptive range, nutrition and medicine effect. A variety of 70 types of grapes are planted on more than 11.6 million plants in Iraq, generating a total annual output of more than 421,000 tons. Increasing grape quality, and particularly the phenolic composition recently has been of major interest. Leaf nutrition – particularly seaweed extracts, being rich in amino acids, trace elements and growth promoting substances – has proved to be a potential tool to enhance plant growth and fruit biochemical quality. The effect of grape variety and fertilizer on the phenolic content in grape fruits (Halwani and Kamali) was investigated using the foliar-applied seaweed extract, Agrimax® at 0, 15 and 30 ml/L were applied. Factorial experiment was carried out in 2024 with completely randomized design by three replications. The first foliar treatment was performed on the first day of April and thereafter five sprays were given at 15 days intervals. HPLC was used to determine the amount of phenolic compounds, such as caffeic, gallic, cinnamic, chlorogenic and p-coumaric acid), The data was analyzed using GenStat with LSD at 5% and two-way ANOVA followed by Šidák test. High phenolic traits were found to be significantly different in all, but caffeic, gallic, and cinnamic acids where the Halwani population extracted with methanol outperformed Kamali. Application of seaweed extract (particularly at 30 ml/L) considerably raised contents of caffeic, gallic, cinnamic and chlorogenic acids in comparison to control plants. The highest levels of all significantly altered phenolics were observed in Halwani variety at the concentration 30 ml/L Agrimax®. The level of p-coumaric acid did not significantly change. In conclusion, the Halwani cultivar had the highest phenolic content under Babil Germplasm climatological conditions. Application of seaweed extract by foliar method particularly at 30 ml/L significantly increased phenolic content, indicating its potential to be used as an eco-friendly substitute to mineral fertilization.