Brenneria populi subsp. brevivirga subsp. nov. isolated from symptomatic bark of Populus × euramericana canker, and description of Brenneria populi subsp. populi subsp. nov.

Two Gram-stain-negative, facultatively anaerobic, motile bacterial strains isolated from symptomatic bark of Populus × euramericana canker in China were investigated using a polyphasic approach, including 16S rRNA gene sequencing, multilocus sequence analysis, and biochemical and physiological assays. 16S rRNA gene sequencing indicated that these strains belonged to the genus Brenneria, family Pectobacteriaceae, and had the highest sequence similarity with Brenneria populi CFCC 11963T (98 %). DNA-DNA hybridization experiments revealed DNA-DNA relatedness values of 72.1-78.2 % between the new isolates and strains of B. populi, revealing that these strains belonged to the same species. The 16S rRNA gene sequencing and multilocus sequence analysis suggested that the two novel strains and those of B. populi are phylogenetically closely related but form two clearly separated subgroups. Based on the data, the two novel isolates represent a subspecies of B. populi for which the name B. populi subsp. brevivirga subsp. nov. is proposed with D8-10-4-5T (=CFCC 11935T=KCTC 42841T) as the type strain, with the automatic creation of B. populi subsp. populi subsp. nov. (type strain D9-5T=CFCC 11963T=KCTC 42088T).