Abstract
Xanthomonas euvesicatoria phage KΦ1, a member of Myoviridae family, was isolated from the rhizosphere of pepper plants showing symptoms of bacterial spot. The phage strain expressed antibacterial activity to all X. euvesicatoria strains tested and did not lyse other Xanthomonas spp., nor other less related bacterial species. The genome of KΦ1 is double-stranded DNA of 46.077 bp including 66 open reading frames and an average GC content of 62.9%, representing the first complete genome sequence published for a phage infecting xanthomonads associated with pepper or tomato. The highest genome similarity was observed between phage KΦ1 and the Xanthomonas oryzae pv. oryzae specific phage OP2. On the other hand, when compared with other members of the genus Bcep78virus, the genome similarity was lower. Forty-four (67%) predicted KΦ1 proteins shared homology with Xanthomonas phage OP2, while 20 genes (30%) were unique to KΦ1. Phage KΦ1, which is chloroform resistant and stable in different media and in the pH range 5-11, showed a high titer storage ability for at least 2 years at +4°C. Copper-hydroxide and copper-oxychloride reduced phage activity proportionally to the used concentrations and the exposure time. UV light was detrimental to the phage strain, but skim milk plus sucrose formulation extended its survival in vitro. The phages survived for at least 7 days on the surface of pepper leaves in the greenhouse, showing the ability to persist on the plant tissue without the presence of the host bacterium. Results of three repeated experiments showed that foliar applications of the unformulated KΦ1 phage suspension effectively controlled pepper bacterial spot compared to the standard treatment and the untreated control. The integration of the phage KΦ1 and copper-hydroxide treatments resulted in an increased efficacy compared to the copper-hydroxide alone.
Highlights
Pepper (Capsicum annuum L.) is one of the major vegetable crops in Serbia, covering approx. 20,000 ha of open fields
Frequent occurrence of plant pathogenic bacteria, ineffective chemical control and increasing environmental concerns certainly have contributed to the increased interest in using bacteriophages for the control of bacterial infections in plants
We studied the host range, genome characteristics, survival, and biocontrol potential of bacteriophage strain K 1 specific to X. euvesicatoria, a causal agent of pepper bacterial spot
Summary
Pepper (Capsicum annuum L.) is one of the major vegetable crops in Serbia, covering approx. 20,000 ha of open fields. Large areas and intensive production, both in the open field and in plastic tunnels and greenhouses, make Serbia one of the leading pepper growing countries in Europe. The occurrence of pepper diseases causes significant losses and occasionally limits successful production. Vesicatoria group A, Jones et al, 2004; Obradovicet al., 2004b), is one of the most important pepper diseases in all pepper growing areas and in Serbia as well (Balaž, 1994; Obradovicet al., 2000, 2001). The development by the pathogen copper or streptomycin resistance (Thayer and Stall, 1961; Marco and Stall, 1983; Adaskaveg and Hine, 1985; Minsavage et al, 1990; Pernezny et al, 1995; Martin et al, 2004) and increased public concern about detrimental effects of pesticide residues initiated efforts in searching for alternatives in control of bacterial diseases
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