Since 2015, necrosis caused by Fusarium spp. has been regularly observed in carrot seed crops in France. A collection of 53 Fusarium isolates was gathered from lesions on carrot between 2016 and 2019. Morphological characterization at both the macroscopic and microscopic levels and molecular typing based on the ACL1, RPB2 and EF1-α partial gene sequences resulted in the identification of two main groups, corresponding to 22 F. avenaceum and 22 F. tricinctum isolates. In addition, three isolates of F. graminearum, two each of F. oxysporum and F. acuminatum, and one isolate of F. solani were also identified. Dual cultures of Trichoderma spp. (T. atroviride and T. harzianum) and Fusarium spp. (F. tricinctum isolate FT001 and F. avenaceum isolate FA002) did not indicate any antibiosis capabilities of Trichoderma. The in vitro sensitivity of isolates FT001 and FA002 to two fungicides and one natural product was similar, with an efficacy depending on the active ingredient. Prothioconazole + tebuconazole was more effective (mycelial growth reduced by 97% for FT001 and 99.8% for FA002) than fluopyram + trifloxystrobin (mycelial growth reduced by 58% and 56%, respectively). Allium extracts seemed to be a promising alternative to fungicides, since they were almost as efficient as prothioconazole + tebuconazole. Artificial inoculation of durum wheat using three isolates from carrot lesions (FT001, FA002 and F. graminearum FG001) induced plant necrosis. This result suggests that Fusarium pathogens of carrot seed crops may be transmitted to wheat, which is commonly used in rotation with carrot.

HomePlant DiseaseVol. 104, No. 2First Report of Root and Collar Rot Caused by Fusarium tricinctum and Fusarium avenaceum on Carrot in France PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Root and Collar Rot Caused by Fusarium tricinctum and Fusarium avenaceum on Carrot in FranceT. Le Moullec-Rieu, C. Chateau, C. Pascouau, F. Bastide, B. Hamon, P. Poupard, E. Laurent, J. Gombert, E. Morel, I. Sérandat, P.-L. Guillermin, P.-E. Brandeis, and S. MallardT. Le Moullec-RieuIRHS, Université d'Angers, INRA, Agrocampus Ouest, SFR 4207 QUASAV, F-49071 Beaucouzé, France, C. ChateauIRHS, Université d'Angers, INRA, Agrocampus Ouest, SFR 4207 QUASAV, F-49071 Beaucouzé, France, C. PascouauIRHS, Université d'Angers, INRA, Agrocampus Ouest, SFR 4207 QUASAV, F-49071 Beaucouzé, France, F. BastideIRHS, Université d'Angers, INRA, Agrocampus Ouest, SFR 4207 QUASAV, F-49071 Beaucouzé, France, B. HamonIRHS, Université d'Angers, INRA, Agrocampus Ouest, SFR 4207 QUASAV, F-49071 Beaucouzé, France, P. Poupard†Corresponding author: P. Poupard; E-mail Address: pascal.poupard@univ-angers.frhttp://orcid.org/0000-0002-4316-5951IRHS, Université d'Angers, INRA, Agrocampus Ouest, SFR 4207 QUASAV, F-49071 Beaucouzé, France, E. LaurentFNAMS, F-49800 Brain-sur-l'Authion, France, J. GombertFNAMS, F-49800 Brain-sur-l'Authion, France, E. MorelFNAMS, BP 23, F-41240 Ouzouer-le-Marché, France, I. SérandatGEVES, F-49071 Beaucouzé, France, P.-L. GuillerminHM CLAUSE, F-49800 La Bohalle, France, P.-E. BrandeisVILMORIN, F-49250 La Ménitré, France, and S. MallardVILMORIN, F-30210 Ledenon, France AffiliationsAuthors and Affiliations T. Le Moullec-Rieu1 C. Chateau1 C. Pascouau1 F. Bastide1 B. Hamon1 P. Poupard1 † E. Laurent2 J. Gombert2 E. Morel3 I. Sérandat4 P.-L. Guillermin5 P.-E. Brandeis6 S. Mallard7 1IRHS, Université d'Angers, INRA, Agrocampus Ouest, SFR 4207 QUASAV, F-49071 Beaucouzé, France 2FNAMS, F-49800 Brain-sur-l'Authion, France 3FNAMS, BP 23, F-41240 Ouzouer-le-Marché, France 4GEVES, F-49071 Beaucouzé, France 5HM CLAUSE, F-49800 La Bohalle, France 6VILMORIN, F-49250 La Ménitré, France 7VILMORIN, F-30210 Ledenon, France Published Online:19 Nov 2019https://doi.org/10.1094/PDIS-11-18-2081-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In 2017, carrot (Daucus carota L.) seed production represented around 22% of the area devoted to the production of vegetable fine seeds. Since 2015, symptoms of root and collar rot have been observed in carrot seed parcels located in the Central Region, one of the most important production zones in France. Diseased plants became dried prematurely, compromising seed development. Depending on the year and the climatic conditions, the disease in a same field can be considered as epidemic (rate losses between 30 and 100% of plants in 2016) or can impact plants more sporadically (less than 10% in 2017 and 2018). Sixteen diseased carrot samples (Nantaise type) were collected from five fields of seed production in the Central Region: two fields in 2016 and 2017, and one field in 2018. Seven fungal isolates, obtained from lesions, were grown on potato dextrose agar medium and incubated for 1 week at 20°C in darkness. From the colony top, fluffy mycelium pigmented in pink, red, purple, or orange was observed, with a red color at the reverse. To induce sporulation, isolates were grown on Synthetischer Nährstoffarmer agar medium during 3 weeks at 24°C with near-UV radiation under a 12-h photoperiod. Four isolates (FT001, FT003, FT007, and FT017) developed orange sporodochia with lunar or crescent-shaped macroconidia (40.3 ± 0.8 × 5.9 ± 0.1 µm; n = 90) and lime or pear-shaped microconidia (10.7 ± 0.2 × 7.7 ± 0.2 µm; n = 60), as described for Fusarium tricinctum (Leslie and Summerell 2006). Three isolates (FA001, FA002, and FA006) developed orange sporodochia with sickle-shaped macroconidia (50.5 ± 1.1 × 5.0 ± 0.1 µm; n = 60) but no microconidia, as observed in Fusarium avenaceum (Leslie and Summerell 2006). To confirm the identification, DNA was extracted from the mycelium of the seven isolates, and molecular markers (ATP citrate lyase, ACL1; RNA polymerase II, RPB2) were used for PCR amplification (Gräfenhan et al. 2011; O'Donnell et al. 2013). The ACL1 sequences from the seven field isolates (GenBank nos. MK183788 to MK183791; MK181528 to MK181530) were 99 to 100% identical to the ACL1 sequence of a reference F. tricinctum isolate (query coverages 99 to 100%; E-values of 0.0) and a reference F. avenaceum isolate (query coverages 98 to 99%; E-values of 0.0) (respectively DAOM 235630 isolate, GenBank no. JX397813, and BBA64135 isolate, GenBank no. JX397768 [Niessen et al. 2012]). Using RPB2, sequences from field isolates (GenBank nos. MK183109 to MK183115) were 98.5 to 99.9% identical to the RPB2 sequence of a reference F. tricinctum isolate (query coverages 96 to 100%; E-values of 0.0) and a reference F. avenaceum isolate (query coverages 95 to 100%; E-values of 0.0) (respectively MRC 1895 isolate, GenBank no. MH582113, and MRC 1413 isolate, GenBank no. MH582082 [O'Donnell et al. 2018]). To confirm pathogenicity, FT001 and FA002 were inoculated on collars of 10-week-old carrot plants in the greenhouse. Forty plants per isolate and 40 control plants were used. Ten microliters of a conidial suspension (105 conidia/ml), or sterile water for the controls, was deposited at the collar, which was previously wounded using a scalpel blade. Necrotic lesions developed at 20 days postinoculation (dpi) (FT001) and at 30 dpi (FA002). F. tricinctum and F. avenaceum were reisolated from the lesions and identified by sequencing using ACL1 and RPB2 markers. No isolation of Fusarium was obtained from the controls. To our knowledge, this is the first report of F. tricinctum and F. avenaceum in carrot in France.The author(s) declare no conflict of interest.References:Gräfenhan, T., et al. 2011. Stud. Mycol. 68:79. https://doi.org/10.3114/sim.2011.68.04 Crossref, ISI, Google ScholarLeslie, J. F., and Summerell, B. A. 2006. The Fusarium Laboratory Manual. Blackwell Publishing, Hoboken, NJ. https://doi.org/10.1002/9780470278376 Crossref, Google ScholarNiessen, L., et al. 2012. Int. J. Food Microbiol. 158:171. https://doi.org/10.1016/j.ijfoodmicro.2012.06.021 Crossref, ISI, Google ScholarO'Donnell, K., et al. 2013. Fungal Genet. Biol. 52:20. https://doi.org/10.1016/j.fgb.2012.12.004 Crossref, ISI, Google ScholarO'Donnell, K., et al. 2018. Mycologia 110:1058. https://doi.org/10.1080/00275514.2018.1519773 Crossref, ISI, Google ScholarThe author(s) declare no conflict of interest.DetailsFiguresLiterature CitedRelated Vol. 104, No. 2 February 2020SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionSymptom of maize ear rot caused by Fusarium sporotrichioides (B. B. Wang et al.). Photo credit: C. X. Duan. Systemic symptoms of alfalfa mosaic virus (AMV) isolate CaM on leaves of potato (X. Z. Nie et al.). Photo credit: X. Z. Nie. Metrics Downloaded 1,586 times Article History Issue Date: 31 Jan 2020Published: 19 Nov 2019First Look: 10 Sep 2019Accepted: 4 Sep 2019 Pages: 591-591 Information© 2020 The American Phytopathological SocietyKeywordsfungivegetablesetiologyThe author(s) declare no conflict of interest.

A collection of 102 Diaporthe isolates was compiled from lesions on carrot, parsley and wild Apiaceae species in France from 2010 to 2014. Molecular typing based on ITS rDNA sequences resulted in the identification of 85 D. angelicae and 17 D. eres isolates. Based on sequences of the 30 part of the IGS rDNA, intraspecific variability was analysed for 17 D. angelicae and 13 D. eres isolates from diverse plant species, locations in France, and plant tissues. The genetic diversity was greater for D. angelicae isolates than D. eres isolates. In vitro sensitivity of five D. angelicae and four D. eres isolates to each of nine fungicides was similar for isolates of both species, with a marked variation in fungicide sensitivity depending on the active ingredient. To assess the pathogenicity of D. angelicae and D. eres isolates on carrot, one isolate of each species was inoculated onto umbels in a controlled environment. Typical lesions were observed for both isolates. Carrot crop debris collected from a seed production field in France and placed in controlled conditions produced perithecia and ascospores typical of Diaporthe, that were further characterized molecularly as belonging to D. angelicae. Detection of Diaporthe species on seed lots from three carrot production fields in France was investigated. Both species were detected on seeds by conventional PCR assay, with a greater frequency for D. angelicae than D. eres (67% vs 33%, respectively). Overall, the results highlighted that umbel browning in carrot seed crops in France was mainly caused by D. angelicae.

In 2011, carrot (Daucus carota L.) seed production occurred on 2,900 ha, which accounts for approximately 25% of the area devoted to the production of vegetable fine seeds. Since 2007, symptoms of umbel browning have been regularly observed in carrot production areas located in the central region. Initially, triangular necrotic lesions appeared on carrot umbels that later spread to the entire umbels and often progressed to the stems. Diseased umbels became dried prematurely, compromising seed development. The loss in seed production was estimated at approximately 8% of the harvested carrot umbels during the cropping seasons of spring and summer 2007 and 2008 in France. In collaboration with seed companies, diseased carrot stems were collected from seven fields of seed production (eight plants per field) and a fungus was isolated from the tissue. The cultures were grown on malt (2%) agar (1.5%) medium and incubated for 2 weeks at 22°C in darkness. Young fungal colonies were white and a brownish green pigmentation developed when the colonies became older. The same color was observed from the top and on the reverse of the colonies. To induce sporulation, isolates were grown on water agar (1.5%) medium in the presence of carrot stem fragments for 1 week at 22°C in darkness, followed by 1 week at 22°C in white light under a 16-h photoperiod. Pycnidia were produced on stem fragments and contained alpha and beta conidia typical of the genus Diaporthe (2). Alternatively, pycnidia were also obtained on malt agar medium after 2 weeks of culture at 25°C in white light under a 12-h photoperiod. The size of alpha and beta conidia was 6.3 ± 0.5 × 2.3 ± 0.4 μm and 23.3 ± 1.8 × 0.9 ± 0.2 μm, respectively (n = 170). In order to confirm the identification at the genus level and determine the species, DNA was extracted from the mycelium of three representative isolates and the ITS regions of the ribosomal DNA were amplified using universal primers (1). The sequences of the amplified products (GenBank Accession Nos. KF240772 to KF240774) were 100% identical with the ITS sequence of a Diaporthe angelicae isolate deposited in the NCBI database (CBS 111592 isolate, KC343027). To confirm pathogenicity, the three isolates of D. angelicae were inoculated on carrot umbels in the greenhouse. A total of nine plants were inoculated (three plants per isolate). Using a micropipette, 10 μl of a conidial suspension containing alpha and beta conidia (105 conidia mL-1) were deposited at the base of the primary umbel and two secondary umbels, which were wounded before inoculation using a scalpel blade. Seven inoculated plants developed triangular, necrotic lesions that were typical umbel browning. D. angelicae was re-isolated on malt agar medium from the inoculated diseased carrot umbels. To our knowledge, this is the first report of D. angelicae in carrot cultivated for seed production in France. The disease resembles the lesions described in the Netherlands in 1951 on carrot inflorescence caused by Phomopsis dauci (3). In future experiments, it would be crucial to precisely determine if D. angelicae could be transmitted to the seeds. References: (1) M. A. Innis et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990. (2) J. M. Santos and A. J. L. Philips. Fungal Divers. 34:111, 2009. (3) J. A. von Arx. Eur. J. Plant Pathol. 57:44, 1951.