Cryphonectria cubensis on an indigenous host in Brazil: a possible origin for eucalyptus canker disease?

Abstract

Endothiella sp. was found associated with witches' broom symptoms of Tibouchina granulosa growing in a stretch of Atlantic rain forest in Rio de Janeiro, Brazil. The fungus was the anamorph of Cryphonectria cubensis the eucalypt canker fungus. Host-range studies were performed involving 40 plant species belonging to 19 families and showed that C. cubensis has a wide potential host-range, concentrated on the Myrtales but including Persea americana (avocado) and Pouteria caimito. These are members respectively of the subclasses Magnoliidae and Dilleniidae, distantly related to plants of the subclass to which both eucalypt and T. granulosa belong (Rosidae). The finding of C. cubensis in balance with a population of a native species at a site isolated and distant from both eucalypt and clove plantations might be regarded as reinforcing the hypothesis of a Neotropical origin for the fungus as opposed to the hypothesis of the fungus being from Oceania and having cloves as its original host. The new alternative hypothesis(of separate origins from endemic hosts in the Neotropics, Africa and Oceania) should nevertheless be also considered.