Lavandula stoechas or French lavender (Labiatae) is a perennial shrub that produces pinkish purple flowers and is endemic to the Mediterranean Region. In the Albenga area (northern Italy), this species is grown as a potted plant. In October 2008, symptoms of a previously unknown blight were observed in a commercial glasshouse in the Savona Province (northern Italy) on 10% of 3-month-old ‘Sugarberry Ruffles’ potted plants. Glasshouse temperatures ranged between 11 and 32°C (average of 21°C) and plants were overhead irrigated. Initially, leaves and stems appeared chlorotic. Subsequently, necrotic lesions developed on infected tissues. After 10 days, fluffy, gray mycelium became apparent on symptomatic tissue, especially on the basal parts of the plants. Severely infected plants eventually died. Tissues were excised from diseased leaves, immersed in an aqueous solution of 1% sodium hypochlorite for 10 s, and then cultured on potato dextrose agar (PDA). A fungus developed abundant mycelium when incubated under constant fluorescent light at 22 ± 1°C. Numerous small sclerotia developed on PDA plates incubated for 20 days at 8 ± 1°C. Sclerotia were dark and irregular and measured 2 to 5 × 1 to 2 mm. Conidia were smooth, gray, unicellular, ovoid, measured 9.4 to 13.6 × 6.2 to 7.9 (average 11.4 × 7.2) μm, and similar to those described for Botrytis cinerea (2). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 573-bp segment was 100% similar to the sequence of Botryotinia fuckeliana (perfect stage of B. cinerea). The nucleotide sequence has been assigned GenBank Accession No. GQ375747. Pathogenicity tests were performed by spraying leaves of 9-month-old healthy potted L. stoechas ‘Blue Star’, ‘Madrid Blue’, ‘Madrid Purple’, and ‘Madrid White’ plants with a 7.5 × 104 conidia/ml spore suspension obtained from 7-day-old PDA cultures. Each plant received 5 ml of inoculum. Plants sprayed with water only served as controls. Four plants per treatment and per cultivar were used. Plants were covered with plastic bags for 4 days after inoculation and maintained in a growth chamber at 20 ± 1°C. The first lesions developed on flowers 5 days after inoculation, and 2 days later, lesions developed on leaves and stems. Lesions were similar to those observed in the commercial glasshouse. Control plants remained healthy. B. cinerea was consistently reisolated from these lesions. The pathogenicity test was completed twice. To our knowledge, this is the first report of the presence of B. cinerea on L. stoechas in Italy as well as worldwide. Botrytis blight previously has been described on L. angustifolia in Japan (4) and Poland (3). In Italy, the economic importance of the disease is currently still limited.
References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, England, 1971. (3) L. B. Orlikowski and A. Valjiuskaite. Acta Mycol, 42:193, 2007. (4) J. Takeuch and H. Horie. Annu. Rep. Kanto-Tosan Plant Prot. Soc. 53:87, 2006.
