IN VITRO EVALUATION OF SOLUBLE SILICON (Si) FOR CONTROLLING VASCULAR STREAK DIEBACK DISEASE OF COCOA (Theobroma cacao)
Authors: Suhaida S., Noor Afiqah M. and Siti Nordahliawate M.S.
Journal Issue: Malaysian Cocoa Journal, Volume 13(2)/2021
Keywords: Vascular streak dieback, silicon, Theobroma cacao
Published On: 1/11/2021
Abstract
Vascular streak dieback (VSD), caused by the fungus Ceratobasidium theobromae has killed large amount of cocoa trees in Papua New Guinea in 1960s to 1970s. The disease has since become a serious problem in Malaysia, Indonesia and the Philippines. Average yield loss due to VSD disease in Malaysia is ranges between 10 to 15%. To date, this disease is managed by several methods such as cultural practices, fungicides and resistant clones. However, none of the above approaches provide sufficient protection to cocoa trees. In this study, soluble silicon (Si) was investigated as potential agent for the control of VSD disease under in vitro conditions. By employing poison plate technique, a plug of C. theobromae growth was cultured on amended coconut water agar (CWA) with Si in five different concentrations (0.5, 1.0, 1.5, 2.0 and 2.5 % v/v). Unamended medium were served as control and each treatment was performed in 7 replicates. After seven days of incubation, results showed that Si had significantly (p ≤ 0.05) suppressing the radial growth of the pathogen. The effectiveness of Si increased with concentration, and the growth of pathogen was almost completely retarded at 2.5 % silicon nutrient (v/v) with percentage inhibition of diameter growth (PIDG) 95.00%. The lowest concentration of silicon nutrient (0.5%) performed the lowest PIDG (54.29%). The results of in vitro study suggest that Si shows a promising agent for inhibiting the pathogen. However, further study is needed to evaluate the potential use of Si in controlling VSD on cocoa seedlings and mature trees.