Main content area

First Report of Botrytis cinerea Causing Gray Mold Disease on the Endemic Plant Echinopsis coquimbana in the Coquimbo Region, Chile

Plaza, V., Bustamante, C., Silva-Moreno, E., Castillo, L.
Plant disease 2018 v.102 no.7 pp. 1448
Botrytis cinerea, Echinopsis, adverse effects, agar, agricultural industry, blueberries, coasts, conidia, crop losses, culture media, environmental impact, flora, fruits, genes, glucose, grapes, gray mold, indigenous species, internal transcribed spacers, kiwifruit, leaves, malt extract, pathogenicity, plant pathogenic fungi, plants (botany), ribosomal DNA, sclerotia, sodium hypochlorite, surveys, tissues, tomatoes, Chile
Botrytis cinerea is a phytopathogenic fungus that infects over 200 plant species and can cause significant crop losses in local and worldwide agricultural industries (Jarvis 1977). However, its presence in the endemic flora in the IV Region of Coquimbo and its impact on local flora have not been studied yet. Echinopsis coquimbana is a member of the Cactaceae family and is widespread and abundant along Coquimbo’s coast (Rundel et al. 1998). Surveys for this fungus were conducted in June 2014 at a single location near Caleta Hornos at 36 km north of La Serena, Chile (29°37′54.48″ S, 71°17′03.04″ W). Findings revealed that 10% of E. coquimbana plants displayed disease symptoms on the base of their spines resembling gray mold disease. Symptoms were observed only at the base of spines, with gray or brownish masses of spores produced in the infected tissues. Gray mold symptoms were not observed on any other parts of the plant. Diseased spine tissues were excised and surface sterilized by immersion in 1% NaOCl for 60 s, placed on malt extract agar (2% malt extract and 2% agar), and incubated at 22°C (Plaza et al. 2015). Fungal colonies obtained were initially white and then became gray to brown after 6 days. Elliptical conidia, measuring 7.9 to 12 μm long and 6.4 to 9.5 μm wide (n = 300), were observed on these colonies. The isolates Bc.eq01 and B05.10 (control strain), incubated at 20 ± 2°C for 21 days, produced blackish, spherical to irregular microsclerotia, ranging from 0.57 to 3.9 mm (width and length, respectively) (n = 400). For molecular characterization of B. cinerea isolate Bc.eq01, fungal genomic DNA was extracted using a DNeasy plant mini kit (Qiagen, Germany) according to the manufacturer’s instructions. The internal transcribed spacer (ITS) sequence region of rDNA was amplified using ITS1/ITS4 primers (White et al. 1990) and then sequenced. ITS analysis of this isolate revealed that it corresponded to genus Botrytis. For further confirmation, nuclear protein-coding genes (G3PDH, HSP60, and RPB2) were sequenced (Staats et al. 2005). Resultant sequences, deposited in GenBank as accessions KY798122 to KY798124, respectively, showed 100% identity against B. cinerea. Isolate Bc.eq01 was used to conduct pathogenicity tests by wound inoculating 5 μl of conidial suspensions (2.5 × 10⁵ conidia/ml in Gamborg B5 + 2% glucose) (Plaza et al. 2015) onto tomato fruits and leaves, as well as to the spine base of E. coquimbana. Both tomato leaves and fruits developed typical gray mold symptoms after 4 days of inoculation; similar symptoms were observed at the spine base of E. coquimbana, and no symptoms were observed on control plants. B. cinerea was reisolated from the inoculated tomato fruit and E. coquimbana lesions. Results provided here contribute to our fundamental understanding of the presence of B. cinerea in an endemic plant from the IV region in Chile, as well as the potentially adverse effects on local agriculture and on other endemic plants. This pathogen has been previously isolated in Chile (from Atacama to Bio-Bio regions) from blueberry, kiwifruit, tomato, and grapes (Muñoz et al. 2002). To the best of our knowledge, this is the first report of B. cinerea causing gray mold on E. coquimbana in Chile. Further studies are required to determine the distribution and ecological impact of this disease on E. coquimbana as well as on other endemic plants.