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Potato (Solanum tuberosum) blackleg and tuber soft rot diseases in Israel, caused by Pectobacterium and Dickeya spp., originate from seed tubers imported from Europe. These diseases are of great concern due to the warm climatic conditions during the growing season that favor disease expression and may result in establishment of the pathogens in potato fields and their spread to weeds and other crops (Tsror et al. 2009). Pectobacterium parmentieri was recently reported in Europe as an emerging threat to potato production, amongst other Pectobacterium and Dickeya spp., (van der Wolf et al. 2017; Suárez et al. 2017; Zoledowska et al., 2018). Surveys for pectinolytic bacteria were carried out during spring 2019, in an experimental plot located at Gilat Research Center Israel (ARO), where different imported seed lots were planted, and during 2017, in a commercial pack house. Pectobacterium parmentieri was detected in diseased potato plants (cv. Sifra), and in wash water sampled during the process of packing ware potato, respectively. Plant material was surface sterilized with 0.3% (v/v) hypochlorite for 3 min, and 10 segments from the stem base of each plant were homogenized with 10 ml sterile distilled water. Sample homogenates were plated on crystal violet pectate medium (CVP). The wash water surveys were done during May, July and August 2017, with processed tubers (cvs. Sifra, Winston, Allians, Evolution, and Rosanna) obtained from commercial spring plots, located in Western Negev, in which imported seeds from Europe were planted in January. Wash water samples (200 ml) were filtered through rough filter paper followed by fine filtering using Millipore (45 µ). The Millipore filter paper was re-suspended in 2 ml sterile distilled water and suspensions were plated on CVP. Single colonies obtained on CVP medium were purified by repeated sub-culturing on nutrient agar (NA, Difco), and selected strains were further characterized. Most of the isolated colonies were identified as P. carotovorum subsp. carotovorum, P. c. subsp. brasiliense or Dickeya solani, however, one isolate from the diseased plants and three isolates from the wash water were characterized as P. parmentieri. DNA extracted from these colonies reacted positively in a qPCR assay based on the YD repeat protein gene PW7011F/R specific primers (Kim et al. 2012) and also in a TaqMan assay based on mdh sequence (van der Wolf et al. 2017). Sequencing the gapA gene (Cigna et al. 2017) identified the isolate as P. parmentieri (GenBank Accession No. MN887102), with 100% similarity to P. parmentieri strain SCC3193 (Accession No. CP003415.1). All four isolates caused maceration of potato tubers at 30°C (Tsror et al. 2013). In a pathogenicity assay with the isolate from the diseased plant and one of the isolates from the wash water, conducted at 30°C on potato plants (cv. Allians), wilting symptoms appeared 48 h after stem inoculation (10 μl bacterial suspension at 108 cells/ml). Re-isolated bacteria from the inoculated plants were confirmed as P. parmentieri by PCR. This is the first report on the presence of P. parmentieri in Israel. These findings are of phytosanitary significance due to the recent reports from Europe, indicating that P. parmentieri has an important role in the pectinolytic bacterial complex causing potato blackleg and thus has the potential to cause disease under warm climate conditions as well.

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First report of Pectobacterium parmentieri one of the causal agents of potato blackleg and tuber soft rot diseases in Israel
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First report of Pectobacterium parmentieri one of the causal agents of potato blackleg and tuber soft rot diseases in Israel

Potato (Solanum tuberosum) blackleg and tuber soft rot diseases in Israel, caused by Pectobacterium and Dickeya spp., originate from seed tubers imported from Europe. These diseases are of great concern due to the warm climatic conditions during the growing season that favor disease expression and may result in establishment of the pathogens in potato fields and their spread to weeds and other crops (Tsror et al. 2009). Pectobacterium parmentieri was recently reported in Europe as an emerging threat to potato production, amongst other Pectobacterium and Dickeya spp., (van der Wolf et al. 2017; Suárez et al. 2017; Zoledowska et al., 2018). Surveys for pectinolytic bacteria were carried out during spring 2019, in an experimental plot located at Gilat Research Center Israel (ARO), where different imported seed lots were planted, and during 2017, in a commercial pack house. Pectobacterium parmentieri was detected in diseased potato plants (cv. Sifra), and in wash water sampled during the process of packing ware potato, respectively. Plant material was surface sterilized with 0.3% (v/v) hypochlorite for 3 min, and 10 segments from the stem base of each plant were homogenized with 10 ml sterile distilled water. Sample homogenates were plated on crystal violet pectate medium (CVP). The wash water surveys were done during May, July and August 2017, with processed tubers (cvs. Sifra, Winston, Allians, Evolution, and Rosanna) obtained from commercial spring plots, located in Western Negev, in which imported seeds from Europe were planted in January. Wash water samples (200 ml) were filtered through rough filter paper followed by fine filtering using Millipore (45 µ). The Millipore filter paper was re-suspended in 2 ml sterile distilled water and suspensions were plated on CVP. Single colonies obtained on CVP medium were purified by repeated sub-culturing on nutrient agar (NA, Difco), and selected strains were further characterized. Most of the isolated colonies were identified as P. carotovorum subsp. carotovorum, P. c. subsp. brasiliense or Dickeya solani, however, one isolate from the diseased plants and three isolates from the wash water were characterized as P. parmentieri. DNA extracted from these colonies reacted positively in a qPCR assay based on the YD repeat protein gene PW7011F/R specific primers (Kim et al. 2012) and also in a TaqMan assay based on mdh sequence (van der Wolf et al. 2017). Sequencing the gapA gene (Cigna et al. 2017) identified the isolate as P. parmentieri (GenBank Accession No. MN887102), with 100% similarity to P. parmentieri strain SCC3193 (Accession No. CP003415.1). All four isolates caused maceration of potato tubers at 30°C (Tsror et al. 2013). In a pathogenicity assay with the isolate from the diseased plant and one of the isolates from the wash water, conducted at 30°C on potato plants (cv. Allians), wilting symptoms appeared 48 h after stem inoculation (10 μl bacterial suspension at 108 cells/ml). Re-isolated bacteria from the inoculated plants were confirmed as P. parmentieri by PCR. This is the first report on the presence of P. parmentieri in Israel. These findings are of phytosanitary significance due to the recent reports from Europe, indicating that P. parmentieri has an important role in the pectinolytic bacterial complex causing potato blackleg and thus has the potential to cause disease under warm climate conditions as well.

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