Occurrence of the virulent strain of Pseudomonas syringae pv. actinidiae in Japan: a case study of a field in Shizuoka Prefecture
Pseudomonas syringae pv. actinidiae (Psa) has been shown to have heterotypic populations including a pandemic highly virulent strain (Psa3 or Psa-V). Although Psa was first recorded in Japan, the virulent strain Psa3 had not been observed until spring of 2014, when the sudden outbreak of Psa3 took place in Japan. Also in Shizuoka Prefecture, we noticed the incidence of bacterial leaf spots in several kiwifruit orchards in June 2014. Isolation of the causal bacterium and identification through PCR and other techniques confirmed that the pathogen was Psa3. In one representative field, the disease was observed on Actinidia deliciosa 'Hayward'. Similar leaf spots were also observed on A. chinensis cultivars planted in the same field, however, the pathogen was identified as a strain of Pseudomonas syringae causing flower-rot (blossom blight) disease of kiwifruit (Ps-fr). The differences between Psa3, Psa1 and Ps-fr were confirmed. Sometimes, Psa3 and Ps-fr were isolated from a single lesion. The transition of the disease incidence from 2014 to 2015 was described. It was demonstrated that Ps-fr inhibited the growth of Psa3 in vitro.
Takikawa, Y., Tsuji, M., Miyazaki, S., Sudo, M. and Yahata, M. (2019). Occurrence of the virulent strain of Pseudomonas syringae pv. actinidiae in Japan: a case study of a field in Shizuoka Prefecture. Acta Hortic. 1243, 49-54
Pseudomonas syringae pv. actinidiae, kiwifruit, Psa1, Psa3, flower-rot, bacterial canker, disease incidence, antagonism