First report of Quambalaria eucalypti in young Eucalyptus plants in field conditions in Brazil

Abstract

The genus Quambalaria includes several important pathogens of Eucalyptus and Corymbia spp., mainly those that cause leaf and shoot blight. The species Quambalaria eucalypti has been reported to be an aetiological agent of this disease in Brazil only in nurseries involved in the production of Eucalyptus minicuttings, where climatic conditions are more favourable for the pathogen. The aim of this study was to identify the pathogen that causes a similar disease in young Eucalyptus trees. For this, we used morphological characteristics, pathogenicity tests and DNA sequence data. Sequences of four isolates obtained from leaves and cankers were compared to 17 sequences deposited in GenBank. Twenty-one isolates were subjected to multilocus analyses of internal transcribed spacer (ITS) and rDNA large subunit (LSU) sequence information. The resulting consensus tree showed that isolates in this study could be grouped with Q. eucalypti into one distinct clade, and the morphological characteristics were similar to those described in the literature. The pathogenicity was confirmed, and the pathogen was re-isolated from inoculated plants, confirming Koch's postulates. This is the first record of Q. eucalypti causing leaf and shoot blight on young Eucalyptus plants in field conditions in Brazil. The presence of this disease in nurseries and its occurrence in the field is cause for alarm in Eucalyptus breeding programmes in Brazil.