Pseudomonas amygdali (syn. Pseudomonas savastanoi ) pv. adzukicola pv. nov., causal agent of bacterial stem rot of adzuki bean

Bacterial stem rot of adzuki bean (BSRA) was first recorded in Japan in 1979. The pathogen was identified as a new species, designated as “ Pseudomonas adzukicola ”. However, due to the lack of a type strain, “ P. adzukicola ” has been recognized as invalid since 1980. In the 2000s, we obtained BSRA isolates and compared them with related Pseudomonas species. Inoculations with the BSRA isolates caused symptoms on adzuki bean, cowpea, hyacinth bean, and kidney bean. Pseudomonas savastanoi pv. glycinea ( Psag ) did not affect adzuki bean, whereas P. savastanoi pv. phaseolicola caused distinct symptoms on adzuki bean and had a different host range from the BSRA isolates. The BSRA isolates were similar to Psag in their bacteriological characteristics except that they utilized dl -α-alanine and l -histidine. Phylogenetic analyses based on four housekeeping genes suggested that the BSRA isolates were closely related genetically to Psag , belonging to P. syringae genomospecies 2 and hrp group IA. However, the rep-PCR results distinguished the BSRA isolates from Psag and the other Pseudomonas species. These results suggest that the BSRA agent is an independent taxon among genomospecies 2 bacteria and that the BSRA agent represents a new pathovar. Because P. amygdali is the oldest legitimate name of the genomospecies 2 bacteria, P. savastanoi should be treated as a synonym of P. amygdali . Therefore, we propose the name P. amygdali (syn. P. savastanoi ) pv. adzukicola pv. nov. for the BSRA pathogen, as pathotype strain AZK-11 (SUPP2776, MAFF212478, ICMP24382).