Phytochemical-induced defense activation in chickpea by Calotropis procera L. extract to control Fusarium wilt

Fungicide application offers a solution for crop protection, but synthetic fungicides pose greater harm to the environment. This study explores the potential of Calotropis procera L. leaf extracts as a nature-friendly alternative to combat Fusarium wilt in chickpea. Methanol (MeOH) extracts were tested at various concentrations (0-6.5%) against Fusarium oxysporum, with complete growth suppression observed at 5% and 6.5%. Bioassay-guided fractionation of the crude extract was performed using n-hexane, dichloromethane (DCM), ethyl acetate (EtOAc), acetone (Ace), and methanol (MeOH). The results indicated that EtOAc and Ace fractions at 0.6% completely inhibited fungal growth. Crude extracts (3.5%, 5%, and 6%) along with EtOAc (0.2% and 0.6%) and Ace (0.2% and 0.6%) fractions were further subjected to phytotoxicity analysis on chickpea seedlings. Among these, the EtOAc-0.6% fraction exhibited the least phytotoxicity. In a pot experiment, the group inoculated with F. oxysporum and treated with the botanical extract (T6) showed a lower disease incidence of 41.7%, compared to 50% in the F. oxysporum-inoculated group treated with carbendazim (T5). T6 also exhibited improved root elongation (124%), seed germination (88.89%), catalase activity (52 U/mg protein), and guaiacol peroxidase activity (26.63 U/mg protein). The highest carotenoid content (1.6 µg/mL) was observed in T5, while the uninoculated group treated with the botanical extract (T4) recorded the highest SOD activity (78.24 U/mg protein). Overall, these findings suggest that the EtOAc-0.6% fraction of C. procera leaf extract could serve as a safer and effective candidate for managing Fusarium wilt in chickpea.