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First Report of Downy Mildew Caused by a Peronospora sp. on Basil in Florida and the United States.
Plant Dis 2009; 93(2):199PD

Abstract

Basil is grown as a specialty crop in greenhouse and field production in Florida and other regions of the United States. Downy mildew on basil (Ocimum basilicum) was detected from four production sites (Collier, Hendry, Miami-Dade, and Palm Beach counties) in south Florida in the fall of 2007, and within months, it was also found in west-central north Florida (Hillsborough County). Incidence reached nearly 100% on some of the affected crops and caused complete yield losses on basil grown both in the field for fresh market and potted herbs market. Symptoms developed during transit on basil that appeared symptomless at harvest. Symptoms initially appeared as yellowing on the lower leaves that was typically delineated by the veins, although in some cases the entire leaf area of the leaf surface was affected. A gray, fuzzy growth was apparent on the abaxial leaf surface. Microscopic observation detected dichotomous branching, hyaline sporangiophores (220 to 750 × 4 to 9 μm) bearing single sporangia. Sporangia were light brown, ovoid to slightly ellipsoid, and measured 14 to 15 × 15 to 18 μm. Oospores were not observed. Leaves of potted basil plants and coleus (Solenostemon scutellarioides) were inoculated with a suspension containing 1 × 105 sporangia/ml and sprayed till runoff (approximately 15 ml per plant) with a hand-held pressurized aerosol canister. Plants were covered with a plastic bag for 24 h and maintained in the greenhouse under ambient conditions. Noninoculated plants served as controls. After 7 days, symptoms typical of downy mildew occurred only on the inoculated basil plants and sporulation was confirmed microscopically. The internal transcribed spacer regions of an isolate collected in Hendry County were sequenced bidirectionally. The consensus sequence was deposited into GenBank (Accession No. FJ346561). Sequence data matched (100% homology) with a Peronospora sp. reported on sweet basil in Switzerland (GenBank Accession No. AY884605) and was similar (99% homology) to an isolate (GenBank Accession No. DQ523586) reported on coleus, although inoculation to coleus failed to confirm pathogenicity on this host. The sequence data also distinguished the isolate from P. lamii (87% homology) previously reported to occur on basil. The pathogen was identified as a Peronospora sp. based on morphological characteristics and sequencing homology (1-3). References: (1) L. Belbahri et al. Mycol. Res. 109:1276, 2005. (2) S. Francis. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 688. CMI, Kew, England, 1981. (3) A. McLeod et al. Plant Dis. 90:1115, 2006.

Authors+Show Affiliations

Southwest Florida Research and Education Center, University of Florida, Immokalee.Everglades Research and Education Center, University of Florida, Belle Glade.Department of Plant Pathology, University of Florida, Gainesville.Department of Plant Pathology, University of Florida, Gainesville.Tropical Research and Education Center, University of Florida, Homestead.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

30764112

Citation

Roberts, P D., et al. "First Report of Downy Mildew Caused By a Peronospora Sp. On Basil in Florida and the United States." Plant Disease, vol. 93, no. 2, 2009, p. 199.
Roberts PD, Raid RN, Harmon PF, et al. First Report of Downy Mildew Caused by a Peronospora sp. on Basil in Florida and the United States. Plant Dis. 2009;93(2):199.
Roberts, P. D., Raid, R. N., Harmon, P. F., Jordan, S. A., & Palmateer, A. J. (2009). First Report of Downy Mildew Caused by a Peronospora sp. on Basil in Florida and the United States. Plant Disease, 93(2), p. 199. doi:10.1094/PDIS-93-2-0199B.
Roberts PD, et al. First Report of Downy Mildew Caused By a Peronospora Sp. On Basil in Florida and the United States. Plant Dis. 2009;93(2):199. PubMed PMID: 30764112.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - First Report of Downy Mildew Caused by a Peronospora sp. on Basil in Florida and the United States. AU - Roberts,P D, AU - Raid,R N, AU - Harmon,P F, AU - Jordan,S A, AU - Palmateer,A J, PY - 2019/2/16/entrez SP - 199 EP - 199 JF - Plant disease JO - Plant Dis. VL - 93 IS - 2 N2 - Basil is grown as a specialty crop in greenhouse and field production in Florida and other regions of the United States. Downy mildew on basil (Ocimum basilicum) was detected from four production sites (Collier, Hendry, Miami-Dade, and Palm Beach counties) in south Florida in the fall of 2007, and within months, it was also found in west-central north Florida (Hillsborough County). Incidence reached nearly 100% on some of the affected crops and caused complete yield losses on basil grown both in the field for fresh market and potted herbs market. Symptoms developed during transit on basil that appeared symptomless at harvest. Symptoms initially appeared as yellowing on the lower leaves that was typically delineated by the veins, although in some cases the entire leaf area of the leaf surface was affected. A gray, fuzzy growth was apparent on the abaxial leaf surface. Microscopic observation detected dichotomous branching, hyaline sporangiophores (220 to 750 × 4 to 9 μm) bearing single sporangia. Sporangia were light brown, ovoid to slightly ellipsoid, and measured 14 to 15 × 15 to 18 μm. Oospores were not observed. Leaves of potted basil plants and coleus (Solenostemon scutellarioides) were inoculated with a suspension containing 1 × 105 sporangia/ml and sprayed till runoff (approximately 15 ml per plant) with a hand-held pressurized aerosol canister. Plants were covered with a plastic bag for 24 h and maintained in the greenhouse under ambient conditions. Noninoculated plants served as controls. After 7 days, symptoms typical of downy mildew occurred only on the inoculated basil plants and sporulation was confirmed microscopically. The internal transcribed spacer regions of an isolate collected in Hendry County were sequenced bidirectionally. The consensus sequence was deposited into GenBank (Accession No. FJ346561). Sequence data matched (100% homology) with a Peronospora sp. reported on sweet basil in Switzerland (GenBank Accession No. AY884605) and was similar (99% homology) to an isolate (GenBank Accession No. DQ523586) reported on coleus, although inoculation to coleus failed to confirm pathogenicity on this host. The sequence data also distinguished the isolate from P. lamii (87% homology) previously reported to occur on basil. The pathogen was identified as a Peronospora sp. based on morphological characteristics and sequencing homology (1-3). References: (1) L. Belbahri et al. Mycol. Res. 109:1276, 2005. (2) S. Francis. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 688. CMI, Kew, England, 1981. (3) A. McLeod et al. Plant Dis. 90:1115, 2006. SN - 0191-2917 UR - https://www.unboundmedicine.com/medline/citation/30764112/First_Report_of_Downy_Mildew_Caused_by_a_Peronospora_sp__on_Basil_in_Florida_and_the_United_States_ L2 - http://apsjournals.apsnet.org/doi/full/10.1094/PDIS-93-2-0199B?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -