Investigation of Measures to Control Epiphytes and Endophytes Present in Nodal Explants of Persea Americana Mill in Its in Vitro Establishment

Significant advancements in micropropagation methods facilitate the commercial cultivation of avocado (Persea americana Mill), a remarkable tropical and sub-tropical fruit, highly recommended for its nutritional value. Since high quality, true-to-type planting materials are required to promote the commercial producti on of avocado, this study was conducted with the objective of investigati ng an eff ective sterilization method to control both epiphytes and endophytes present in nodal explants of P. americana cv. ‘Pollock’ to optimize in vitro establishment measures which will lead to popularize its micropropagation. In this study, nodal segments of approximately 10 cm from soft wood stem cuttings of P. americana cv ‘Pollock’ were used to obtain explants. The effects of 10%, 20%, and 30% concentrations of sodium hypochlo- rite (NaOCl) were evaluated, with exposure durations of 10 and 20 minutes, to determine their efficacy in eliminating epiphytes during vitro establishment. Additionally, the nodal explants were treated with 100 mg/L Augmenti n™ for 20 - minutes and 30 - minutes periods respectively, as a final dip before culturing to eradicate endophytes. The effects of three different culture media, half-strength Murashige and Skoog (MS) medium, Woody Plant Medium (WPM), and Gamborg’s medium (B5) were also investigated. The highest survival rate (83%) of nodal segments was achieved when explants were sterilized with 20% Na- OCl for 20 minutes, followed by a final sterilization step involving a 30-minute dip in Augmenti n™, and subsequently cultured in WPM medium. Keywords: Avocado; In vitro propagation; Nodal segments; Sodium Hypochlorite