A serological approach for the identification of the effector hopz5 of Pseudomonas syringae pv. actinidiae: a tool for the rapid immunodetection of kiwifruit bacterial canker

Pseudomonas syringae pv. actinidiae (Psa) is responsible for outbreaks of kiwifruit canker over the world, and the cause of heavy economic losses. Although molecular detection methods for this bacterium are well-established, its serological detection is much less advanced. A polyclonal antiserum to the bacterial effector-hopz5 was raised (PAb:hopz5) and its specificity tested. No cross-reaction was observed with other bacteria, including Pseudomonas syringae pv. tomato, Pseudomonas syringae pv. theae, Pseudomonas putida, Pseudomonas fluorescens, Pseudomonas koreensis, Bacillus subtilis, Bacillus megaterium, Ralstonia solanacearum, Erwinia rhapontica, Pseudomonas syringae pv. syringae. PAb:hopz5 was able to detect Psa from culture and infected plant samples, thus representing a suitable tool for the immunodetection of the agent of kiwifruit bacterial canker in field samples. The detection sensitivity of a colloidal gold immunochromatographic strip was high, up to 2.2 × 103 CFU/ml. Thus PAb:hopz5 constitutes a suitable and accurate tool for detection of Psa and haplotype distribution.