Induction of Bioactive Secondary Metabolites in Annona cherimola Mill. (Chirimoya) Seedlings Using Chitosan and Salicylic Acid as Elicitors

The use of elicitors such as salicylic acid (SA) and chitosan (CH) represents an effective strategy to induce the production of secondary metabolites in plants. However, its application in seedlings of Annona cherimola Mill. has been scarcely explored. This study evaluated the effect of different concentrations of SA (100, 250 and 400 μM) and CH (60, 80 and 100 μM) applied foliar on phenological growth, accumulation of phenolic compounds and flavonoids, and antioxidant activity in Annona cherimola. Three weekly treatments were applied under controlled conditions. Total phenolic content (TPC) was quantified as milligrams of gallic acid equivalents per gram of dry mass (mg GAE/g DW) of extract, and total flavonoid content (TFC) as milligrams of quercetin equivalents per gram of dry mass (mg QE/g DW) of extract. Antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method and the ferric reducing antioxidant power (FRAP) assay, and results were expressed as milligrams of Trolox equivalents per gram of dry mass (mg TE/g DW) of extract. The results showed that salicylic acid 100 μM and chitosan 80 μM promoted the highest stem growth and leaf count. These concentrations also induced the highest content of phenols (up to 23.5 mg GAE/g DW) and flavonoids (15.5 mg QE/g DW), as well as higher antioxidant activity (up to 21.5 mg TE/g DW). A positive correlation was observed between the accumulation of metabolites and the antioxidant capacity. This is the first report to validate the use of salicylic acid and chitosan as biostimulant tools to modulate physiology and secondary metabolism in Annona cherimola (Chirimoya).