First Report of Cadophora luteo-olivacea Causing Side Rot on Kiwifruit in Chile

Abstract

HomePlant DiseaseVol. 102, No. 3First Report of Cadophora luteo-olivacea Causing Side Rot on Kiwifruit in Chile PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Cadophora luteo-olivacea Causing Side Rot on Kiwifruit in ChileJ. Auger, I. Pérez, C. Osorio-Navarro, and M. EsterioJ. Auger†Corresponding author: J. Auger; E-mail: E-mail Address: jauger@uchile.clSearch for more papers by this author, I. PérezSearch for more papers by this author, C. Osorio-NavarroSearch for more papers by this author, and M. EsterioSearch for more papers by this authorAffiliationsAuthors and Affiliations J. Auger † I. Pérez C. Osorio-Navarro M. Esterio , Laboratorio de Fitopatología Frutal y Molecular, Facultad de Ciencias Agronómicas, Universidad de Chile, C.P. 8820808, La Pintana, Santiago, Chile. Published Online:9 Jan 2018https://doi.org/10.1094/PDIS-09-17-1349-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Kiwifruit (Actinidia deliciosa [Chev] Ling et Ferguson cv. ‘Hayward’) can be stored for over 6 months at 0 ± 1°C. However, in recent years a postharvest disease of kiwifruit, characterized by a side rot appearing during harvest or after 3 to 6 months postharvest cold storage period, has been observed in several packinghouses in central Chile. Symptoms on kiwifruit were depressed and elliptical areas, associated with brown-violet skin and brown pulp. Symptomatic kiwifruit samples from different packinghouses were sterilized with 75% (v/v) ethanol, and infected tissue was placed onto potato dextrose agar (PDA) at 24°C in the dark for a 7-day period. Single spore colonies were flat, felty, and cottony in the middle, with smooth margins, with an even edge and varying in color from white turning to gray/black-olivaceous. Microscopically, straight, septate, short conidiophores had mostly cylindrical monophialides with hyaline collarettes. Conidia (n = 50) from four representative isolates recovered from naturally infected kiwifruit (2VCBC, 2VCBD, 2VCBF, and 2VCCD) were hyaline, unicellular, oblong elliptical or ovoid, and mostly biguttulated, measured 3.8 to 5.8 × 2.2 to 3.5 µm (mean, 2.9 × 4.8 µm). Cultural and morphological pathogen characteristics were similar to those described for Cadophora sp. (Gramaje et al. 2011). Three loci (ITS, β-tubulin, and EF1-α) of the four representative isolates were sequenced using the primers ITS1/ITS4, Bt2a/Bt2b, and EF1-728F/EF1-986R (Travadon et al. 2015). BLAST analysis revealed ITS, β-tubulin, and EF1-α sequences (accessions nos. MF464553, MF464555, MF464558, and MF464562) to share 99 to 100% identity with Cadophora luteo-olivacea isolates in GenBank (accession nos. KT350592, KT350591, and KU720079); the sequences (accession nos. MF464554, MF464556, MF464559, and MF464563) were compared with those of C. luteo-olivacea in the NCBI GenBank database and had 99% nucleotide sequence identity (accession nos. KF764682, KF764648, and KF764647), and the sequences (accession nos. MF772484, MF772481, MF772482, and MF772480) were 100% identical to C. luteo-olivacea sequences in GenBank (accession nos. KT350599, KT350598, and KT350597), respectively. Twenty ‘Hayward’ kiwifruits (per representative isolates) were wounded-inoculated in the fruit equatorial region with 20 μl of a spore suspension (106 conidia/ml) prepared from a 15-day-old PDA culture and incubated at 24°C in darkness. Typical symptoms appeared between 8 and 12 days. Kiwifruits inoculated with sterile distilled water remained symptomless. Fungi isolated from the lesions had morphological characteristics that resembled the original isolates from infected fruits. The identity of the reisolations was confirmed as C. luteo-olivacea by sequencing, thus completing Koch’s postulates. C. luteo-olivacea has been identified associated with a similar symptom (skin pitting) on kiwifruit stored long-term in Italy (Piano at al. 2001; Spadaro et al. 2010). In kiwifruit orchards, C. luteo-olivacea is normally a soil-borne microorganism and may be transported into packing houses on fruit skins or in harvest bins (Gilardi et al. 2007). Side rot caused by C. luteo-olivacea represents an economically significant problem for the kiwifruit packinghouses in Chile, owing to the lack of effective postharvest fungicides and the limited knowledge of the pathogen and disease epidemiology. To our knowledge, this is the first report of side rot of kiwifruit caused by C. luteo-olivacea in Chile.