S06 - Session O9 - Pre-harvest factors such as biostimulant application and plant density modulate basil aroma and bioactive compounds in controlled environment.

Authors: Michele Ciriello *, Luigi Formisano, Christophe El-Nakhel, Stefania De Pascale, Youssef Rouphael

Despite its exotic origin, basil ( Ocimum basilicum L.) is cultivated worldwide for its sought-after aromatic leaves. The ample variability in its biochemical composition has given this aromatic herb a multitude of culinary uses. In Italy, 'Genovese' basil leaves are used to make pesto, a condiment that has attracted the interest of consumers and producers. The urge to have a premium quality product with standardized technological characteristics has pushed the research community to look for innovative and sustainable solutions that can ensure high yields and superior quality traits. Yield, technological characteristics, and bioactive compound accumulation depend primarily on pre-harvest factors such as genetic material, environmental factors, and growing conditions. For example, hydroponic growing systems such as the floating raft system (FRS) could improve the nutritional value of basil by applying eustress through careful management of the nutrient solution. However, nutritional quality traits can be affected by agronomic practices such as biostimulant application and density. For example, high planting density (317 plants m n2 ) in FRS reduced the number of leaves per plant (n27.8%) while increasing fresh (+31.4%) and dry (+30.4%) yield per unit area, compared to the half density (159 plants m n2 ), without altering the flavor profile of basil cultivars 'Eleonora' and 'Italiano Classico'. When compared to the control treatment, the application of a plant biostimulant based on protein hydrolysates (Trainer ® ) in the nutrient solution resulted in an average increase in the number of leaves (+10.9%), fresh yield (+13.8%) and dry yield (+17.1%), total phenols (+24.4%) and linalool (+7.9%), a sought-after compound characterizing the flavor of 'Genovese' basil. The in-depth knowledge of how different pre-harvest factors influence basil production and the improvement of its nutritional value by adapting it to the current needs of consumers would allow to meet the needs of modern agriculture, which requires high yields, high qualitative attributes and sustainability.