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First Report of Downy Mildew Caused by Hyaloperonospora camelinae on Camelina sativa in Slovenia.
Plant Dis 2014; 98(10):1439PD

Abstract

Camelina or false flax (Camelina sativa), of the Brassicaceae, is an annual flowering plant native to Europe and Central Asia where it is grown commercially as an oilseed crop. At the end of May 2012, symptoms of downy mildew were observed on camelina plants grown in the Savinja Valley in Slovenia. The disease was found in four monitored fields (total area 3 ha), and the incidence ranged from 2 to 38% depending on the variety. Symptomatic plants showed whitish, abundant, and fluffy mycelia covering the stems, flowers, seed pods, and undersides of the leaves. The disease mainly affected the upper half of the plants, and the stems were reduced and distorted. During disease progression, the mycelium turned from gray to black. Microscopic observations revealed hyaline, straight conidiophores that were branched monopodially (3 to 4 times) with 6 to 12 re-curved tips/branch, and measured 140 to 300 × 12 to 20 μm. Conidia were hyaline, oval to broadly ellipsoidal, 24 to 29 × 18 to 24 μm. Oospores formed in necrotic stem and leaf tissues were dark brown and measured 30 to 38 μm in diameter. Based on these morphological characteristics, the causal agent was identified as Hyaloperonospora camelinae (1,3,4,5). DNA was extracted from mycelium and conidia collected from infected plants in two fields in the Savinja Valley (1HpC and 2HpC). Nuclear internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) were amplified by PCR assay from two isolates using the universal primers ITS4 and ITS5, and sequenced. Both samples yielded a 781-bp sequence, which showed 100% identity to H. camelinae ITS sequence JX445136 in GenBank. The nucleotide sequence was assigned to GenBank Accession No. KJ768405. Pathogenicity was confirmed by spraying 25 3-week-old plants of C. sativa cv. Ligena planted in pots (5 plants/pot) with a conidial suspension (105 conidia/ml) obtained from 10 infected plants of the same variety collected from the field 1HpC. Inoculated plants were covered with polyethylene bags for 2 days to maintain high humidity, and incubated at 20°C with a 12-h photoperiod/day in a growth chamber. Downy mildew symptoms first developed on leaves 6 days after inoculation. An additional 25 control plants sprayed with sterilized distilled water and otherwise treated similarly to the inoculated plants developed no symptoms. The identity of the pathogen on the inoculated plants as H. camelinae was confirmed based on the morphological features described above. Downy mildew of false flax caused by H. camelinae has been reported in Europe from Austria, Bulgaria, Germany, Poland, Portugal, Spain, and Switzerland (2); and in the United States from Florida, Oregon, Minnesota, Montana, Nebraska, and Washington (1,3,4,5). To the best of our knowledge, this is the first report of downy mildew caused by H. camelinae on C. sativa in Slovenia. The representative samples were deposited in the phytopatological herbarium of the Slovenian Institute of Hop Research and Brewing. References: (1) E. M. Babiker et al. Plant Dis. 96:1670, 2012. (2) D. F. Farr and A. Y. Rossman, Fungal Databases, Syst. Mycol. Microbiol. Lab. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ . (3) R. M. Harveson et al. Plant Health Progress. doi: 10.1094/PHP-2011-1014-01-BR, 2011. (4) M. L. Putnam et al. Plant Health Progress. doi: 10.1094/PHP-2009-0910-01-BR, 2009. (5) P. Srivastava et al. Plant Dis. 96:1692, 2012.

Authors+Show Affiliations

Slovenian Institute of Hop Research and Brewing, Cesta Zalskega Tabora 2, SI-3310, Zalec, Slovenia.Slovenian Institute of Hop Research and Brewing, Cesta Zalskega Tabora 2, SI-3310, Zalec, Slovenia.Slovenian Institute of Hop Research and Brewing, Cesta Zalskega Tabora 2, SI-3310, Zalec, Slovenia.Slovenian Institute of Hop Research and Brewing, Cesta Zalskega Tabora 2, SI-3310, Zalec, Slovenia.University of Ljubljana, Biotechnical Faculty, Agronomy Department, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

30703972

Citation

Radisek, S, et al. "First Report of Downy Mildew Caused By Hyaloperonospora Camelinae On Camelina Sativa in Slovenia." Plant Disease, vol. 98, no. 10, 2014, p. 1439.
Radisek S, Ceh B, Luskar MO, et al. First Report of Downy Mildew Caused by Hyaloperonospora camelinae on Camelina sativa in Slovenia. Plant Dis. 2014;98(10):1439.
Radisek, S., Ceh, B., Luskar, M. O., Jakse, J., & Javornik, B. (2014). First Report of Downy Mildew Caused by Hyaloperonospora camelinae on Camelina sativa in Slovenia. Plant Disease, 98(10), p. 1439. doi:10.1094/PDIS-05-14-0459-PDN.
Radisek S, et al. First Report of Downy Mildew Caused By Hyaloperonospora Camelinae On Camelina Sativa in Slovenia. Plant Dis. 2014;98(10):1439. PubMed PMID: 30703972.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - First Report of Downy Mildew Caused by Hyaloperonospora camelinae on Camelina sativa in Slovenia. AU - Radisek,S, AU - Ceh,B, AU - Luskar,M Oset, AU - Jakse,J, AU - Javornik,B, PY - 2019/2/2/entrez PY - 2014/10/1/pubmed PY - 2014/10/1/medline SP - 1439 EP - 1439 JF - Plant disease JO - Plant Dis. VL - 98 IS - 10 N2 - Camelina or false flax (Camelina sativa), of the Brassicaceae, is an annual flowering plant native to Europe and Central Asia where it is grown commercially as an oilseed crop. At the end of May 2012, symptoms of downy mildew were observed on camelina plants grown in the Savinja Valley in Slovenia. The disease was found in four monitored fields (total area 3 ha), and the incidence ranged from 2 to 38% depending on the variety. Symptomatic plants showed whitish, abundant, and fluffy mycelia covering the stems, flowers, seed pods, and undersides of the leaves. The disease mainly affected the upper half of the plants, and the stems were reduced and distorted. During disease progression, the mycelium turned from gray to black. Microscopic observations revealed hyaline, straight conidiophores that were branched monopodially (3 to 4 times) with 6 to 12 re-curved tips/branch, and measured 140 to 300 × 12 to 20 μm. Conidia were hyaline, oval to broadly ellipsoidal, 24 to 29 × 18 to 24 μm. Oospores formed in necrotic stem and leaf tissues were dark brown and measured 30 to 38 μm in diameter. Based on these morphological characteristics, the causal agent was identified as Hyaloperonospora camelinae (1,3,4,5). DNA was extracted from mycelium and conidia collected from infected plants in two fields in the Savinja Valley (1HpC and 2HpC). Nuclear internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) were amplified by PCR assay from two isolates using the universal primers ITS4 and ITS5, and sequenced. Both samples yielded a 781-bp sequence, which showed 100% identity to H. camelinae ITS sequence JX445136 in GenBank. The nucleotide sequence was assigned to GenBank Accession No. KJ768405. Pathogenicity was confirmed by spraying 25 3-week-old plants of C. sativa cv. Ligena planted in pots (5 plants/pot) with a conidial suspension (105 conidia/ml) obtained from 10 infected plants of the same variety collected from the field 1HpC. Inoculated plants were covered with polyethylene bags for 2 days to maintain high humidity, and incubated at 20°C with a 12-h photoperiod/day in a growth chamber. Downy mildew symptoms first developed on leaves 6 days after inoculation. An additional 25 control plants sprayed with sterilized distilled water and otherwise treated similarly to the inoculated plants developed no symptoms. The identity of the pathogen on the inoculated plants as H. camelinae was confirmed based on the morphological features described above. Downy mildew of false flax caused by H. camelinae has been reported in Europe from Austria, Bulgaria, Germany, Poland, Portugal, Spain, and Switzerland (2); and in the United States from Florida, Oregon, Minnesota, Montana, Nebraska, and Washington (1,3,4,5). To the best of our knowledge, this is the first report of downy mildew caused by H. camelinae on C. sativa in Slovenia. The representative samples were deposited in the phytopatological herbarium of the Slovenian Institute of Hop Research and Brewing. References: (1) E. M. Babiker et al. Plant Dis. 96:1670, 2012. (2) D. F. Farr and A. Y. Rossman, Fungal Databases, Syst. Mycol. Microbiol. Lab. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ . (3) R. M. Harveson et al. Plant Health Progress. doi: 10.1094/PHP-2011-1014-01-BR, 2011. (4) M. L. Putnam et al. Plant Health Progress. doi: 10.1094/PHP-2009-0910-01-BR, 2009. (5) P. Srivastava et al. Plant Dis. 96:1692, 2012. SN - 0191-2917 UR - https://www.unboundmedicine.com/medline/citation/30703972/First_Report_of_Downy_Mildew_Caused_by_Hyaloperonospora_camelinae_on_Camelina_sativa_in_Slovenia_ L2 - http://apsjournals.apsnet.org/doi/full/10.1094/PDIS-05-14-0459-PDN?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -