R.W. Barreto*, F.B. Rocha and F.A. Ferreira

Departamento de Fitopatologia, Universidade Federal de Viçosa, 36571-000, Viçosa-MG, Brazil

*rbarreto@ufv.br

Accepted for publication 10/11/05

Eucalyptus is the most important plant genus for forest plantations worldwide, including Brazil where approximately three million hectares are cultivated. Chrysoporthe cubensis (formerly known as Cryphonectria cubensis) is the etiological agent of eucalyptus canker; one of the worst diseases of eucalypt. Although in the past this fungus was only known to attack eucalyptus and cloves, it is now known to attack other hosts in the Myrtaceae and Melastomataceae families (Seixas et al., 2004; Wingfield, 2003; Rodas et al., 2005). 

Figure 1: Healthy (right) and Chrysoporthe cubensis infected trunk base (left) of Marlierea edulis	Figure 2: Chrysoporthe cubensis - section through perithecium (bar = 10 µm)

A host range study involving wound inoculations with an isolate from eucalyptus indicated a potentially wide host range for this fungus, particularly within the order Myrtales (Seixas et al. 2004). Among the species found susceptible in this test was Marlierea edulis, popularly known in Brazil as cambucá. This is a large, native tree of the Brazilian tropical rainforest and minor fruit tree occasionally grown as a curiosity in orchards.

Figure 3: Chrysoporthe cubensis – asci with ascospores (bar = 10 µm)

Recently, M. edulis was found in the field (Saquarema, state of Rio de Janeiro, Brazil) showing typical canker symptoms: necrotic wounds with cracking and flaking of the bark that led to branch death. Diseased tissue showed abundant black spine-like perithecial ostioles. The fungus had the typical morphology of C. cubensis: ascomata perithecial, subglobose 205–445x220–440 µm, ostioles rostrate 300–750x65–125 µm; asci unitunicate, clavate 15–28x3–5 µm; ascospores ellipsoid, 5–7x1–3 µm, one septate and hyaline. A sample was deposited in the local herbarium (VIC 27828).

Figure 4: Corymbia citriodora branch showing abundant formation of sporulating perithecia around inoculation wound, three weeks after inoculation	Figure 5: Marlierea edulis branch showing abundant formation of sporulating perithecia around inoculation wound, five weeks after inoculation

Wound inoculations of an isolate obtained from this host using the bark-replacement method (Ferreira, 1989) on adult, healthy specimens of both M. edulis and Corymbia citriodora (=Eucalyptus citriodora), resulted in typical canker symptoms and abundant formation of sporulating C. cubensis perithecia after three weeks. This is the first record of natural infection by this fungus on M. edulis and the third native host for this fungus to be found in the field in Brazil. This finding confirms the susceptibility under natural conditions of plants included in the host-range study performed by Seixas et al. (2004). The demonstration of pathogenicity of an isolate obtained from M. edulis to eucalyptus represents additional evidence for the hypothesis that native plants serve as reservoirs for eucalyptus canker outbreaks in Brazil.

Ferreira FA, 1989. Patologia florestal; principais doenças florestais no Brasil Viçosa, Brazil: Sociedade de Investigações Florestais.

Rodas CA, Gryzenhout M, Myburg H, Wingfield BD, Wingfield MJ, 2005. Discovery of the Eucalyptus canker pathogen Chrysoporthe cubensis on native Miconia (Melastomataceae) in Colombia. Plant Pathology 54, 460-470.

Seixas CDS, Barreto RW, Alfenas AC, Ferreira FA, 2004. Cryphonectria cubensis on an indigenous host in Brazil: a possible origin for eucalyptus canker disease? Mycologist 18, 18-24.

Wingfield AJ, 2003. Increasing threat of diseases to exotic plantation forests in the Southern Hemisphere: lessons from Cryphonectria canker. Australasian Plant Pathology 32, 133-139.

The British Society for Plant Pathology