![]() ![]() theobromae obtained from infected cacao plants sampled from Indonesia and Malaysia. In this study, DNA was extracted from pure cultures of O. The pathogen is known only to infect cacao, an introduced crop it is suspected to occur asymptomatically in native vegetation but the pathogen cannot be isolated reliably and cultures cannot be maintained. Basidia that develop on leaf scars release airborne basidiospores to infect young leaves. Eventually the shoot apex is killed and infected branches die back and may occasionally lead to death of the cacao plant. ![]() The symptoms of the disease include green-spotted chlorosis and/or marginal necrosis and leaf senescence beginning on the second or third flush of leaves behind the stem apex, raised lenticels, and darkening of vascular traces at the leaf scars and infected xylem. Technical Abstract: Vascular Streak Dieback (VSD) disease of cacao (Theobroma cacao) in Southeast Asia and Melanesia is caused by a basidiomycete (Ceratobasidiales) fungus described in a monotypic genus as Oncobasidium theobromae (syn. This DNA method allows pathologists to determine whether cacao material is infected with the disease-causing fungus before symptoms appear and thus to prevent the spread of the disease to new areas. A second, related species was discovered for the first time in cacao in Indonesia. Its relationship to other plant pathogenic fungi was determined and, as a result, a new name for the fungal pathogen is proposed. In the present research we have developed a method to identify the pathogen using a highly specific DNA-based method. ![]() This species only occurs on the chocolate plant and cannot be grown in culture. This disease is only known from that region and is caused by a fungus. Interpretive Summary: The most serious disease of the chocolate plant in Southeast Asia is known as Vascular Streak Dieback (VSD). Vascular Streak Dieback of cacao in Southeast Asia detection and Melanesia: in planta detection of the pathogen and a new taxonomy. Citation: Samuels, G.J., Ismaiel, A.A., Rosmana, A., Junaid, M., Cubeta, M., Rodriguez-Carres, M., Guest, D., Mcmahon, P., Keane, P., Purwantara, A., Lambert, S. ![]()
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