CERATOCYSTIS MANGINECANS AND NOT C. FIMBRIATA A THREAT TO PROPAGATED ACACIA SPP. IN SABAH, MALAYSIA

Acacia mangium plantations in Sabah, Malaysia are seriously affected by a vascular wilt and canker disease caused by a species of Ceratocystis. A similar and devastating disease occurs in Indonesia and is caused by the fungal pathogen Ceratocystis manginecans. A closely related fungus, Ceratocystis fimbriata sensu stricto, is a common soil-borne pathogen of sweet potato (Ipomoea batatas) in areas of Malaysia where A. mangium is grown. This study characterised the species causing wilting on A. mangium and compared it with the I. batatas pathogen using DNA sequence-based comparisons used artificial inoculations to assess the effect of the A. mangium pathogen on Acacia auriculiformis and Acacia crassicarpa and considered the ability of the sweet potato pathogen to cause disease on the three Acacia species. DNA sequence comparisons confirmed that isolates from diseased A. mangium were C. manginecans and those on sweet potato were C. fimbriata s.s. Ceratocystis manginecans was pathogenic on all Acacia spp., with A. mangium being most susceptible followed by =A. auriculiformis and A. crassicarpa. Pathogenicity tests showed that C. fimbriata s.s. from sweet potato is not able to cause disease on any of the three Acacia spp. considered. This study also confirmed that C. manginecans is the primary cause of ceratocystis canker and wilt disease in Sabah and that the sweet potato fungus, C. fimbriata s.s., poses no threat to propagated Acacia spp.