First Report of Botrytis Blight Caused byBotrytis cinereaonCalendula officinalisin Italy

Abstract

HomePlant DiseaseVol. 101, No. 1First Report of Botrytis Blight Caused by Botrytis cinerea on Calendula officinalis in Italy PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Botrytis Blight Caused by Botrytis cinerea on Calendula officinalis in ItalyA. Garibaldi, D. Bertetti, P. Pensa, S. Franco Ortega, and M. L. GullinoA. GaribaldiSearch for more papers by this author, D. BertettiSearch for more papers by this author, P. PensaSearch for more papers by this author, S. Franco OrtegaSearch for more papers by this author, and M. L. GullinoSearch for more papers by this authorAffiliationsAuthors and Affiliations A. Garibaldi D. Bertetti P. Pensa S. Franco Ortega M. L. Gullino , Centre of Competence for the Innovation in the Agro-Environmental Sector (AGROINNOVA), 10095 Grugliasco, Italy. Published Online:24 Oct 2016https://doi.org/10.1094/PDIS-07-16-1016-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Calendula officinalis (pot marigold) is an annual herbaceous plant belonging to the Asteraceae family, appreciated for the abundant production of gaudy inflorescences. In Liguria region (northern Italy), this species is grown as potted plant and for cut flower production. In March 2016, symptoms of a previously unknown blight were observed on 7-month-old potted plants of C. officinalis. Plants were growing in a farm located in Albenga (Savona Province). Symptoms appeared on leaves, petioles, stems, and inflorescences. Affected leaves and petioles appeared chlorotic and later became rotted, starting from the inside foliage. A soft, gray mycelium appeared on symptomatic tissues, especially on leaves inside the foliage. Stems appeared dark and necrotic. Ligules of inflorescences rolled, wilted, and desiccated. Severely affected plants eventually died. Approximately 30% of 2,500 plants presented the symptoms. Diseased tissues were excised and immersed in a solution of sodium hypochlorite (1%) for approximately 10 s, then washed in sterilized water. Successively, small pieces of affected leaves, petioles, stems, and ligules were cultured on potato dextrose agar (PDA) medium, incubated at temperatures ranging from 20 to 23°C. A fungus developed constantly and produced branched conidiophores with unicellular, ovoid conidia measuring 12.7 to 7.7 × 9.1 to 5.4 (average 9.6 × 7.2) µm. Colonies, stored for approximately 20 days at 8 ± 1°C, produced dark, spheroidal to elongated sclerotia measuring 0.5 to 2.1 mm. These characteristics allowed to identify the isolates from C. officinalis as Botrytis cinerea (Ellis 1971). The internal transcribed spacer (ITS) region of rDNA for the isolate DB16APR03 recovered from an affected leaf was amplified using the primers ITS1/ITS4 (White et al. 1990) and sequenced. BLAST analysis (Altschul et al. 1997) of the 455-bp sequence (GenBank accession KX458182) had 100% similarity with several sequences of B. cinerea, among these KT582111. To confirm pathogenicity, three 9-month-old healthy plants of C. officinalis were artificially inoculated with the isolate DB16APR03. A conidial and mycelial suspension (4 × 105 conidia and mycelial fragment/ml) obtained from 10-day old PDA pure cultures of the pathogen was sprayed on leaves (25 ml/plant). Three control plants were sprayed with sterilized water only. All plants were maintained inside a climatic chamber, in a high humidity chamber for 5 days, at 26 to 27°C (daily average temperatures) and 76 to 88% RH. Four days after the inoculation, first symptoms of chlorosis appeared only on inoculated leaves that, successively, diseased. About 11 days after the inoculation, all inoculated plants appeared desiccated, whereas controls remained healthy. Before inoculated plants died, B. cinerea was easily reisolated from affected tissues. No colonies developed from reisolations attempted from controls. B. cinerea was reported on C. officinalis in the United States (Cash 1953), Scotland, and China. This is the first report of B. cinerea on C. officinalis in Italy. The economic importance of this disease might increase, due to the increasing production of C. officinalis in Italy, especially as potted plant.