First Report of a Garlic Bulb Rot Caused by Erwinia persicina in Europe

Abstract

HomePlant DiseaseVol. 99, No. 5First Report of a Garlic Bulb Rot Caused by Erwinia persicina in Europe PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of a Garlic Bulb Rot Caused by Erwinia persicina in EuropeL. Gálvez, J. Gil-Serna, M. García-Díaz, and D. PalmeroL. GálvezSearch for more papers by this author, J. Gil-SernaSearch for more papers by this author, M. García-DíazSearch for more papers by this author, and D. PalmeroSearch for more papers by this authorAffiliationsAuthors and Affiliations L. Gálvez J. Gil-Serna , Universidad Politécnica de Madrid (UPM), EUIT Agrícola, 28040 Madrid, Spain M. García-Díaz , Plant Genetic Resources Centre, INIA, 28800 Alcalá de Henares, Spain D. Palmero , Universidad Politécnica de Madrid (UPM), EUIT Agrícola, 28040 Madrid, Spain. Published Online:29 May 2015https://doi.org/10.1094/PDIS-11-14-1195-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In July 2013, symptoms of pinkish rot were observed in postharvest Chinese type garlic bulbs (Allium sativum L.) collected from Tembleque (Toledo, Spain). Fifty percent of the bulbs displayed symptoms of pink soft rot in at least one clove showing the pink color along all the flesh. Symptomatic cloves were surface disinfested for 3 min in a 2% sodium hypochlorite solution, rinsed twice with sterilized distilled water, and cultured for 2 days in trypticase soy agar (TSA). Gram-negative, oxidase negative, catalase positive, and facultatively anaerobic, motile, rod-shaped bacteria that were positive for glucose fermentation and nitrate reductase were consistently isolated from symptomatic tissues. Single colonies were light beige, circular, convex with entire margins, and pink-pigmented in PDA but not in TSA. Partial sequences of the 16S rRNA gene (1,386 bp) of two of the isolated bacterial strains were obtained using the primer pair p8FPL and p806R (McCabe et al. 1999) and deposited in EMBL database (accession nos. LM651373 and LM651372). BLAST analysis of the 16S rDNA sequences showed a 99% nucleotide sequence identity with the corresponding sequences of this gene previously available on the NCBI database of Erwinia aphidicola (accession no. NR_104724), E. persicina (NR_114078), and E. rhapontici (KF500098). Additionally, the gene encoding the RNA polymerase beta subunit was sequenced using primers ErpoBF (5′-GGACATGATCAACGCCAAGCCAA-3′) and ErpoBR (5′-GCACCCATCAATGCGCGGTTG-3′) designed in this work on the basis of different species of Erwinia genus. The sequences (581 bp, accession nos. KP100068 and KP100067) showed high identity (99%) with those of E. persicina previously available in databases (i.e. JF311799 and HQ393635) and 97% with the same gene in E. rhapontici (JF311793 and JF311794). The identification was completed with the sorbitol (positive result) and xylitol (negative) fermentation tests that confirmed the strains as E. persicina (Moretti et al. 2011). Pathogenicity tests were performed on Chinese garlic cloves using two E. persicina isolates. Ten cloves were disinfected in 5% sodium hypochlorite solution for 20 min and rinsed twice with sterile distilled water. Thereafter, cloves were wounded with a 200 µl pipette sterile tip (5 mm depth) and inoculated with 10 µl of bacterial suspension (adjusted to a concentration of 107 CFU/ml of TSB) using an automatic pipette. Subsequently, cloves were incubated in petri dishes with a paper towel that was soaked with sterilized distilled water. Ten control cloves were wounded and inoculated with sterilized TSB as negative controls. Inoculated garlic cloves were incubated at 28°C for 10 days in the dark. Pink rot symptoms were observed after 5 days on the inoculated cloves. Control cloves remained symptomless and no bacterium was reisolated. The experiment was repeated once obtaining the same results in both cases. All bacteria reisolated from the pink lesions were identified as E. persicina using the methodology described above. E. persicina has been previously isolated from lucerne, soybean, bean, and pea (González et al. 2007; Zhang and Nan 2014). To our knowledge, this is the first report of clove rot caused by E. persicina in garlic in Europe.