Black root rot caused by Rosellinia pepo, a new disease of the clove tree in Brazil

Abstract

The clove tree is an evergreen plant of the family Myrtaceae that reaches more than 12 meters in height. It originates from the Moluccas, Indonesia, and was introduced in Brazil by the Portuguese. The plant is cultivated mainly in the Lower South region of the state of Bahia, which is also where cacao is grown in Brazil. Cloves are mainly used for culinary purposes, both whole and in ground forms. During disease surveys in the municipality of Itubera, Bahia, in 2006, clove trees were observed showing symptoms of wilting, chlorosis and death, with the dry leaves remaining attached to the branches for some time. Occasionally, especially on older plants, only part of the tree exhibited such symptoms, with leaves falling and leaving the plant defoliated. Up to the collar level, diagnostic disease symptoms and signs of the pathogen were observed on the root system. Beneath the bark, white mycelial fans, star-like, typical of the fungus Rosellinia pepo, were observed on the wood. The anamorph, Dematophora sp., was isolated in PDA and inoculated on four-month-old clove plants, after being cultivated for twenty days in a medium prepared with maize flour and pieces of dry cacao leaves (1:1 w/w). The first disease symptoms and the signs of the pathogen were observed 32 days after inoculations, with the fungus being re-isolated from all the inoculated plants. This is the first report of R. pepo on the clove tree.