Pectobacterium carotovorum subsp. carotovorum Causing Severe Soft Rot in Celeriac on a Family Farm in Slovakia

Palkovics, László and Takács, Georgina and Végh, Dominik (2025) Pectobacterium carotovorum subsp. carotovorum Causing Severe Soft Rot in Celeriac on a Family Farm in Slovakia. ACTA AGRONOMICA ÓVÁRIENSIS, 66 (2). pp. 32-46. ISSN 1416-647X

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Abstract

In 2023 and 2024, soft rot caused significant losses (20-50 %) in celeriac (Apium graveolens var. rapaceum) on a family farm in southern Slovakia. Affected tubers exhibited watery rot, tissue collapse, and a foul odour, particularly evident 12-24 hours after washing. Four bacterial isolates were obtained from the margin of healthy and diseased tissue. All isolates were Gram-negative. Colony morphology and growth characteristics were recorded on potato dextrose agar. Pathogenicity was confirmed by Koch’s postulates using detached celeriac tuber slices; three isolates induced rapid soft rot within 3 days, whereas one isolate produced no symptoms. A 1300 bp fragment of the 16S rRNA gene was amplified with universal primers 63F/1389R, bidirectionally sequenced, and compared with NCBI databases. Three pathogenic isolates were identified as Pectobacterium carotovorum subsp. carotovorum (99.45-99.92 % identity to strains from potato and Chinese cabbage, from China, Iraq and South-Korea). Phylogenetic analysis using the neighbourjoining method placed them within the P. carotovorum clade. The non-pathogenic isolate was identified as Stenotrophomonas sp. High infection rates in fields previously free of root crops suggest contamination originated in greenhouse seedling production. Replacement of greenhouse soil, disinfection of seedling trays, and strict hygiene during post-harvest washing are recommended to prevent recurrence.

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