Characterization of dominant fungal contamination and integration of some “Generally Regarded as Safe” additives for control in natural rubber sheets

Abstract

Importance of the work: Thailand is one of the world's largest exporters of latex and rubber sheets. However, fungal contamination during rubber sheet drying remains a major problem affecting product quality and economic value. Objectives: To identify fungal pathogens associated with rubber sheet diseases and to evaluate environment-friendly control treatments in vitro to support improved disease management strategies. Materials and Methods: Fungal samples were isolated from contaminated rubber sheets and cultured on potato dextrose agar. Morphological observation and molecular analysis of the internal transcriber spacer (ITS)1-5.8S-ITS2 region and the β-tubulin gene were used for identification. The antifungal efficacy was investigated of three food additives (potassium sorbate, sodium bicarbonate, sodium carbonate) at three different concentrations (1%, 2%, 3%) to evaluate their effectiveness against the pathogen. Results: A combination of morphological and molecular analyses identified the pathogen as Aspergillus tamarii Kita (1913), a common contaminant known for its resilience and ability to thrive in humid conditions. The tested antifungal and “Generally Regarded as Safe” additive treatments showed that sodium bicarbonate, particularly at concentrations of 1% and higher, was highly effective in completely inhibiting both the mycelial growth and spore germination of A. tamarii. Based on these findings, sodium bicarbonate, a commonly used and safe food additive, could serve as a promising solution for controlling A. tamarii in rubber sheets. Main finding: This research provided the first scientific evidence confirming A. tamarii infection in natural rubber sheets and demonstrated the potential of sodium bicarbonate as an environment-friendly and practical antifungal strategy for large-scale, industrial rubber sheet production.