Evaluation of Chemical Sterilization Strategies for Nodal Segment Explants of Elo (Ficus racemosa L.): Challenges in Controlling Fungal Contamination

Elo (Ficus racemosa L.) is a woody species of ecological and pharmacological importance whose in vitro establishment is constrained by microbial contamination. This study evaluated chemical sterilization strategies for nodal segment explants obtained from two ex vitro plant sources at Universitas Brawijaya: the Botanical Garden (BIO) and the Electrical Engineering parking area (TE). The experiment was conducted in three stages using a Completely Randomized Design. Stage 1 assessed plant source and 70% ethanol immersion durations of 5, 10, and 15 minutes within three sterilization series (S1, S2, and S3). Stage 2 compared culture media supplemented with (A) 3 mL/L Plant Preservative Mixture (PPM™) or (B) a combination of 200 mg/L Benlox 50 WP and 250 mg/L streptomycin, using TE explants. Stage 3 evaluated PPM™ concentrations of 3, 5, and 7 mL/L. Explant condition and fungal and bacterial contamination were assessed seven days after culture initiation. In Stage 1, explants from TE produced 12.8% uncontaminated viable cultures, whereas BIO produced none. Across 70% ethanol treatments, uncontaminated viable explants were 0%, 7.5%, and 11.7% for the 5 (S1), 10 (S2), and 15 (S3) minute treatments, respectively, with no significant differences among treatments. In Stage 2, all treatments exhibited high levels of fungal contamination, although S2TEA still produced 6.7% uncontaminated viable cultures. In Stage 3, fungal contamination remained 96.7–100%, and only the 5 mL/L PPM™ treatment produced 3.3% uncontaminated viable cultures. Overall, contamination remained predominantly fungal, and none of the tested treatments consistently established aseptic nodal cultures.