Abstract
Pseudomonas syringae pv. eriobotryae causes serious stem canker in loquat (Eriobotrya japonica) trees. This study was conducted to determine whether plasmids are involved with its virulence. The strain NAE89, which belonged to the B group, harbored two plasmids at approximately 6.2 and 50 Mdal that caused stem canker and halo leaf spots on loquat plants. Following digestion with BamHI and ligation into the BamHI cloning site of the broad range host cosmid pLAFR3, four DNA fragments at 3.8, 6.6, 12.3, and 22.8 kb were generated. Although the plasmid-encoded virulence gene psvA was undigested with the BamHI, the halo leaf spot gene may be adjacent to the psvA gene was digested. A pLAFR3 cosmid clone was introduced into the non-pathogenic PE0 and NAE89-1 strains by triparental matings and the pathogenicity was recovered. As a result, the pLAFR3 cosmid clone was introduced into the largest size DNA fragment of 22.8 kb and determined to be the causal agent of canker on the stem of the loquat. This study revealed that the psvA gene, previously found in the 50 Mdal plasmid, was also observed in the 22.8 kb DNA fragment.
Highlights
Pseudomonas syringae pv. eriobotryae is a pathogenic bacterium that causes stem canker in loquat trees
The plasmid-encoded virulence gene psvA was undigested with the BamHI, the halo leaf spot gene may be adjacent to the psvA gene was digested
A pLAFR3 cosmid clone was introduced into the non-pathogenic PE0 and NAE89-1 strains by triparental matings and the pathogenicity was recovered
Summary
Pseudomonas syringae pv. eriobotryae is a pathogenic bacterium that causes stem canker in loquat trees. Eriobotryae is a pathogenic bacterium that causes stem canker in loquat trees. All of the three bacterium groups cause pathogenicity to the stems of loquat plants. Several studies were conducted to determine the involvement and expression of plasmids with regards to virulence gene(s) such as the halo bright pathogen of bean, Pseudomonas savastanoi pv. A potential vir gene, designated virPphA, restored virulence to bean when introduced into the cured race 7 strain RW60 [18]. It was reported that the resistance to loquat canker (group A) controlled by a single dominant gene, designated as Pse-a [15]. Eriobotryae as mentioned above, little information was available on the B strain group, which uniquely caused both stem canker and halo leaf spot (Supplement 1). This study was conducted to investigate the pathogenic expression of the plasmids in the B strain group
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