Optimization of Surface Sterilization Protocol for in Vitro Initiation of African Star Grass (Hypoxis Schimperi)

Abstract

The micropropagation of African star grass (Hypoxis schimperi) is often hindered by microbial contamination, necessitating an optimized surface sterilization protocol for effective tissue culture initiation. This study investigated the effects of different concentrations and exposure times to sodium hypochlorite (NaOCl) on the initiation of Hypoxis schimperi corm explants. Experiments were conducted at the Egerton University Tissue Culture Laboratory. The study used a completely randomized design (CRD) with factorial treatment combinations of concentration and exposure time replicated thrice. Data were analyzed using SAS (version 9.4) and Microsoft Excel. Corm explants were collected from Njombe-Tanzania, incubated in a growth chamber at 28°C ± 2°C, and exposed to artificial illumination of 2000–2500 lx for 16 h daily over 15 days. Sodium hypochlorite (1%, 2%, 3%, and 4%) was tested at varying exposure times 10 and 15 min each. The results indicated that the highest contamination rate (93.3%) was observed when explants treated with 1% NaOCl for 10 min, whereas the lowest contamination rate (46.7%) occurred in explants treated with 4% NaOCl for 15 min. The optimal treatment was determined to be 4% NaOCl for 15 min, which yielded a survival rate of 53.3%. This optimized protocol offers a reliable foundation for initiating micropropagation of Hypoxis. schimperi, supporting its conservation and potential for large-scale propagation in medicinal plant biotechnological programs.