Calonectria species diversity on eucalypts in Indonesia

Diseases increasingly threaten the rapidly expanding eucalypt plantation industry of Indonesia. Of these, leaf blight caused by Calonectria spp. is considered amongst the more important problems, causing losses both in production nurseries and plantations. Using DNA sequence data based on the translation elongation factor 1-alpha, β-tubulin, calmodulin, and histone H3 gene regions, 163 isolates of Calonectria spp. obtained from diseased eucalypt seedlings in nurseries and infected leaves in plantations were identified as Calonectria acicola, C. hawksworthii, C. lombardiana, C. multiseptata, C. pseudoreteaudii and C. reteaudii. Of these, C. lombardiana was by far the most commonly isolated and accounted for approximately 84% of the isolates. Given the predominance of this fungus, it is interesting that it has not previously been reported from Indonesia. This is also the first report of C. pseudoreteaudii and C. acicola from the country. All six species of Calonectria were found to be pathogenic to eucalypts in artificial inoculation studies. Calonectria lombardiana was generally the most pathogenic species and eucalypt genotypes displayed different levels of susceptibility, providing confidence that disease caused by this fungus can be reduced by selecting disease-tolerant planting stock.