Abstract
Pseudomonas syringae pv. actinidiae (Psa) is a Gram-negative bacterium that causes bacterial canker disease in kiwifruit. Copper or antibiotics have been used in orchards to control this disease, but the recent emergence of antibiotic-resistant Psa has called for the development of a new control agent. We previously reported that the bacteriophage (or phage) PPPL-1 showed antibacterial activity for both biovar 2 and 3 of Psa. To investigate the possibility of PPPL-1 to control bacterial canker in kiwifruit, we further tested the efficacy of PPPL-1 and its phage cocktail with two other phages on suppressing disease development under greenhouse conditions using 6 weeks old kiwifruit plants. Our results showed that the disease control efficacy of PPPL-1 treatment was statistically similar to those of phage cocktail treatment or AgrimycinTM, which contains streptomycin and oxytetracycline antibiotics as active ingredients. Moreover, PPPL-1 could successfully kill streptomycin-resistant Psa isolates, of which the treatment of BuramycinTM carrying only streptomycin as an active ingredient had no effect in vitro. The phage PPPL-1 was further characterized, and stability assays showed that the phage was stable in the field soil and at low temperature of 0 ± 2 °C. In addition, the phage could be scaled up quickly up to 1010 pfu/mL at 12 h later from initial multiplicity of infection of 0.000005. Our results indicate that PPPL-1 phage is a useful candidate as a biocontrol agent and could be a tool to control the bacterial canker in kiwifruit by Psa infection in the field conditions.
Highlights
Bacterial canker caused by Psa has been considered as the most devastating disease in both Actinidia deliciosa and Actinidia chinensis [1,2,3]
These assays were repeated three times with the similar results. These results indicate that the pretreatment of PPPL-1 phage can efficiently control bacterial canker in kiwifruit as much as the treatment of the antibiotics product
BuramycinTM did not suppress bacterial growth of streptomycin-resistant Psa isolates at all, while it caused the formation of clear zone against only Psa strain KBE9, a streptomycin-sensitive isolate (Figure 4a,b). Both AgrimycinTM and PPPL-1 phage formed clear zones against all Psa strains, and their antibacterial activities were statistically very similar at p < 0.05, the sizes of clear zones slightly varied among Psa isolates. These results indicate that PPPL-1 phage could be used to control streptomycin-resistant Psa isolates like antibiotics products
Summary
Bacterial canker caused by Psa has been considered as the most devastating disease in both Actinidia deliciosa (green kiwifruit) and Actinidia chinensis (yellow kiwifruit) [1,2,3]. Psa was first isolated in Japan in 1984 [11], and sporadic outbreaks were reported in Korea [4,12], Portugal [13], Spain [14], France [15], Turkey [16], Slovenia [17], Greece [18], and Georgia [19]. In Korea, several Psa strains belonging to biovar 2 were isolated from green kiwifruit cv. Biovar 3 strains, which was first isolated in Italy in 2008 [1], appeared in
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
