Xanthomonas perforans: a tomato and pepper pathogen associated with bacterial blight and dieback of Eucalyptus pellita seedlings in Indonesia

Abstract

Leaf and shoot blight, often accompanied by die-back symptoms, on Eucalyptus species, hybrids and clones have been reported from a number of countries. More than one bacterial species has been found to cause these symptoms. In this study, a leaf disease of E. pellita in Indonesia was investigated. The disease was found primarily on nursery plants and young trees that recovered within the first year of growth. Leaf samples were collected from symptomatic trees, and isolations consistently yielded a Xanthomonas sp. Sequencing of the 16S rRNA gene region and multilocus sequence analysis (MLSA) was performed on 19 of the 61 Xanthomonas isolates obtained. In the MLSA, four genes, namely, dnaK, fyuA, gyrB and rpoD, were sequenced and the isolates were identified as X. perforans. Four representative isolates, at a concentration of 106 CFU/ml, were leaf-infiltrated and spray-inoculated on to E. pellita, tomato and pepper seedlings. The type isolate of X. perforans was included in the pathogenicity trials as a positive control. All four isolates of X. perforans, inclusive of the type isolate, induced bacterial spot symptoms on tomato and pepper seedlings. They also caused water-soaked lesions on the leaves of E. pellita seedlings, characteristic of the symptoms observed in the field. This is the first report of X. perforans infecting leaves of a woody host.