Characterization of isolates of Xanthomonas arboricola pv. corylina, the causal agent of bacterial blight, from Oregon hazelnut orchards

Abstract

Bacterial blight (Xanthomonas arboricola pv. corylina (Xac)) of hazelnut (Corylus avellana L.) was described first in Oregon in 1915 and is now recognized as a damaging disease of young hazelnut trees worldwide. Thousands of hectares of new hazelnut cultivars that are resistant to eastern filbert blight (Anisogramma anomala) are being planted in the Willamette Valley of Oregon, where 99% of the US hazelnut crop is grown. Reports of bacterial blight on young hazelnut trees have increased but information about the causal pathogen is limited. Isolates were recovered from tissues with bacterial blight symptoms that were then characterized for their ability to grow on semi-selective media, their nutrient utilization profiles using Biolog GN2, quinate metabolism, copper tolerance, hypersensitive response on tobacco, and pathogenicity on hazelnut. Additionally, isolates were identified with a duplex PCR assay (ftsX and qumA), 16S rRNA sequence, and multi-locus sequence analysis (MLSA) using rpoD and gyrB. Pathogenic isolates were identified as Xac using morphological, biochemical, molecular, and host assays. Using MLSA, Xac isolates from Oregon separated into two clades, one clade with the type strain and a second clade previously described using isolates from Europe. The phylogenetic diversity of Xac observed in other countries also is present in Oregon.