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Downy mildew of sweet basil ( Ocimum basilicum ) caused by Peronospora sp. in Argentina
Author(s) -
Ronco L.,
Rollán C.,
Choi Y. J.,
Shin H. D.
Publication year - 2009
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/j.1365-3059.2008.02006.x
Subject(s) - basilicum , downy mildew , ocimum , biology , sweet basil , conidium , botany , genbank , genus , herbarium , horticulture , biochemistry , gene
In May 2007, powdery mildew of Madagascar periwinkle (Catharanthus roseus} was observed on commercially grown plants (cv. Yellow Magic) at Kanagawa prefecture. Usually, the white powdery dusting of the fungus developed on the upper leaf surfaces, but it was also seen on the lower leaf surfaces. Symptoms sometimes included yellow and brown lesions (approximately 3-10 mm in diameter) in association with whitish masses of conidiophores and conidia. For pathogenicity testing, conidia on the leaf surface of diseased plants were collected with a dry brush and trans ferred to each of five healthy leaves of C. roseus. These plants were kept at approximately 23°C and symptoms developed on one of the five leaves after 10 days. Fungal morphology on the leaves was as follows: hyphae were branched and hyaline, lacking fibrosin bodies; conidiophores arose from the internal hyphae, and were septate, hyaline and cylindrical, 52-77 x 16-18 pm in diameter; conidia were also hyaline and cylindrical, 35^5 x 13-20 pm in diameter, produced singly; and appressoria were of a simple lobed type. These morphological characteristics corresponded to an anamorph stage of the genus Oidium, subgenus Pseudoidium, which belong to the genus Erysiphe. For more specific identification by DNA analysis, the ITS 1-5*8S rDNAITS 2 region was amplified. The sequence (GenBank Accession No. AB355647) was most similar to that of Erysiphe elevata (AY587014: 99%). However, E. elevata is reported to be a pathogen of Bignoniaceae (Cook et al., 2006). Furthermore, chasmothecia were not observed on leaves of Madagascar periwinkle, and until a chasmothecium is found, this pathogen will be referred to as Erysiphe sp. Powdery mildews on C. roseus have been recorded as Leveillula taurica in India and Korea (Amano, 1986; Shin 2000), and Oidium sp. in Tanzania and Venezuela (Amano, 1986). The reported powdery mildew of C. roseus is not endophytic and the conidiophore does not emerge through the stomata of the host. This feature is obviously different from that of L. taurica. This is the first record of powdery mildew caused by the genus Erysiphe of Madagascar periwinkle in Japan.