Contents lists available at ScienceDirect Postharvest Biology and Technology journal homepage: www.elsevier.com/locate/postharvbio Efciency of essential oils against Pectobacterium carotovorum subsp. carotovorum causing potato soft rot and their possible application as coatings in storage Habibeh Hajian-Maleki a , Sareh Baghaee-Ravari a, ⁎ , Mohammad Moghaddam b a Department of Plant Protection, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran b Department of Horticultural Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran ARTICLE INFO Keywords: Essential oil Pathogenicity determinants Pectobacterium carotovorum subsp. carotovorum Potato Postharvest Soft rot ABSTRACT This research was conducted to exploit an innovative approach for potato soft rot disease management by application of natural compounds as coatings. The activity of three novel essential oils (EOs) extracted from indigenous plants including Hyssopus officinalis, Satureja khuzistanica and Zataria multiflora was investigated against Pectobacterium carotovorum subsp. carotovorum (Pcc) under in vitro and in vivo conditions. The efect of sub-MIC concentrations of the oils was analyzed on diferent pathogenicity determinants of Pcc including mo- tility, bioflm forming activity and enzyme secretion. The potential of the EOs to reduce soft rot was also evaluated in tuber maceration trial and under semi-practical storage conditions. The efect of the EOs application on decay progression and prevalence in potato tubers was determined by in vivo preventing and curing assays. The highest suppressive efects were displayed by S. khuzistanica and Z. multiflora EOs with MIC at 0.19 and 0.38gL −1 . Studied compounds were considerably able to inhibit virulence determinants of Pcc with higher efciency than streptomycin. Bioflm-forming ability was sharply repressed in tested strains within the range of 24.8–47.6%. A signifcant induced motility was observed in oil-treated cells which is adversary with surface adhesion and bioflm development. Secretion of plant cell wall degrading enzymes (PCWDEs) was decreased in the range of 37.6–100% and among them, pectate lyase (Pel) and polygalacturonase (Peh) were considerably inhibited (53.4–100% and 65.4–100%). Sub-MIC values of S. khuzistanica and Z. multiflora EOs led to reduce maceration ability of Pcc strains in the range of 1.4 to 2.9 times compared with control. The results of in vivo trial indicated that tuber rot development was more efciently controlled in preventive than curative conditions. Disease incidence was reduced by 38.4–70.6% as compared with non-coated samples in preventing assessment. In conclusion, the EOs were capable to control soft rot disease under in vitro and in vivo conditions. GC-MS analysis revealed that cis-pinocamphone, carvacrol and thymol were the main active constituents in H. officinalis, S. khuzistanica and Z. multiflora volatile oils, respectively. Studied test phytochemicals could be promising an- tibacterial agents for preserving potato tubers against soft rot and preventing storage loss. This is the frst report on the activity of herbal antimicrobial compounds against a postharvest bacterial disease of potato as a practical solution which can be suggested as preserver coatings for the tubers and incorporated with other disease management strategies. 1. Introduction Potato (Solanum tuberosum) in production and storage process can be damaged by a large variety of pests and diseases. One of the major and widespread bacterial diseases of potato is soft rot. Pectobacterium sp. is one pectolytic genus belonging to Enterobacteriaceae family and generally known as a tissue maceration agent (Czajkowski et al., 2015). Sixty host species are reported for this genus (Ma et al., 2007) and among them potato is the most important one (Andresen, 2012). Among all Pectobacterium species, Pectobacterium carotovorum subsp. carotovorum (Pcc) has the widest range of host plants worldwide and leads to high fnancial losses in potato industry every year (Pinhero and Yada, 2016). This subspecies causing potato tuber decay is a prevalent agent of maceration under bulk storage conditions in Iran (Baghaee- Ravari et al., 2011, 2013) and able to survive in soil and infected host organ for more than one year (Cariddi and Sanzani, 2013). Disease https://doi.org/10.1016/j.postharvbio.2019.06.002 Received 22 January 2019; Received in revised form 12 May 2019; Accepted 5 June 2019 ⁎ Corresponding author. E-mail address: s.baghaee@ferdowsi.um.ac.ir (S. Baghaee-Ravari). Postharvest Biology and Technology 156 (2019) 110928 0925-5214/ © 2019 Elsevier B.V. All rights reserved. T