Contamination control conditions for the in vitro sowing of orchid seeds

Orchids are highly valued for their ornamental and economic importance, with increasing demand for their cultivation in horticulture and the floral industry. However, the in vitro sowing of orchid seeds presents considerable challenges, particularly regarding contamination control, which is critical for successful germination. This issue becomes even more pronounced in laboratories with limited infrastructure, where the absence of a laminar flow hood necessitates methodological adaptations. This study aimed to evaluate the effectiveness of various contamination control strategies by analyzing the impact of pH, culture medium composition, inoculation techniques, light regimes, and fungicide (Chlorothalonil) application on the contamination rate and germination potential of Cattleya perrinii and Cattleya bicolor seeds. Both species are endemic to Brazil and possess significant conservation value. Three experimental conditions were tested: E1 (control), E2 (pH adjustment with a synthetic medium), and E3 (light regime alteration and fungicide application). The results indicated that E2, which involved pH optimization and the use of a synthetic medium, significantly reduced contamination, achieving a contamination index (CI) of 0%. In contrast, E3, which involved changes in light exposure and fungicide application, resulted in a CI ranging from 50% to 70%, with no significant reduction in contamination levels. These findings suggest that effective contamination control is achievable even in the absence of a laminar flow hood, particularly when pH and culture medium are appropriately adjusted. This highlights the feasibility of implementing the protocol in low-cost settings, such as small-scale laboratories or conservation initiatives. While pH and culture medium composition have proven effective without compromising seed germination, other factors, including light exposure and fungicide treatment, exhibited minimal or no influence on contamination control. Further methodological refinements are necessary, in particular regarding these variables' independent and combined effects, to enhance the reproducibility and consistency of the in vitro sowing process.