Archivio Journal of Plant Pathology

Abstract:

In the summer of 2015, potato plants exhibiting blackleg symptoms were surveyed in 10 commercial fields in Amasya province in the Black Sea Region of Turkey. Average disease incidence was approximately 11% in the surveyed area, but could reach up to 40%. Stem tissue of diseased plants was homogenised and extract was plated on Nutrient Agar (Himedia, India). After 24 h incubation at 28°C single colonies were purified on Luria Agar (Himedia, India) or Crystal Violet Pectate (CVP) medium (Hyman et al., 2001). A total of nine strains that were cavity forming on CVP, gram-negative, catalase positive and facultative anaerobic with pectinolytic ability, produced a 434 bp product with pel gene specific primers Y1/Y2 (Darrasse et al., 1994) designed for Pectobacterium spp. One of these strains (A4G1) produced a 322 bp fragment typical for Pectobacterium carotovorum subsp. brasiliense using the subspecies specific primers (Br1f/Lr1) in the PCR assay (Duarte et al., 2004). Blastn analysis with a 1402 bp partial 16S rDNA gene sequence of strain A4G1 (GenBank Accession No. KX548227) showed 99% similarity to the 16S rDNA of P. carotovorum subsp. brasiliense strain 1001 (JF926759) at the nucleotide level. Phylogenetic tree analysis based on the Maximum Likelihood method, using 16S rDNA sequences avaliable in GenBank, clustered the two strains together. Surface sterilized whole potato tubers (cv. Marabel) were stabbed with a sterile pipette tip and inoculated with a 20 μl suspension of 108 cfu ml-1 of an overnight culture grown at 28 ̊C. Inoculation wounds were covered with mineral oil to maintain partly anaerobic conditions in a dew chamber at 26°C. Strain A4G1 caused soft rot of tubers after 48 h incubation. Reisolated colonies caused pitting on CVP and exhibited the same morphology as original cultures on the NA plates. To our knowledge, this is the first report on the presence of P. carotovorum subsp. brasiliense in Turkey.