In vitro growth induction of Ceratobasidium theobromae, the causal agent of cacao Vascular Streak Dieback disease

Abstract

Vascular Streak Dieback (VSD) disease, caused by Ceratobasidium theobromae, has devastated cacao plants in Indonesia and other countries. However, there is limited information on the biology of the fungus, including mass propagation method. This study aimed to find a technique in inducing the growth of C. theobromae as inoculum sources. The stages of research were sampling the plant cacao tissue infected by C. theobromae; induction of mycelia growth on infected cacao tissue using coconut water, glucose, and sucrose; and confirmation C. theobromae by morphology, pathogenicity test on cacao seedling, and genetic. We found characteristic symptoms of VSD disease in cocoa plantations marked by chlorosis in cocoa leaves and blackening of the node on the leaf petiole. The growth induction of C. theobromae could be performed using a 2% glucose solution. The hyaline hyphae, perpendicular branching of hyphae, and a dolipare septate were shown in the hyphae structure. Pathogenicity test of mycelia C. theobromae from infected plant tissue showed typical symptoms of VSD. Genetic confirmation by PCR method successfully amplified specific target DNA of C. theobromae resulted in ± 550 bp amplicon. The result could be performed to propagate C. theobromae inoculum for various purposes in studying VSD disease.