New Disease Reports (2011) 23, 16. [http://dx.doi.org/10.5197/j.2044-0588.2011.023.016]
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First report of Cercospora beticola on lettuce (Lactuca sativa) in Benin

J.H. Hotegni Houessou 1, F. Beed 1*, R. Sikirou 2 and V. Ezin 1

*f.beed@cgiar.org

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Received: 28 Sep 2010; Published: 04 Apr 2011

Leafy vegetables such as lettuce are important components of daily diets in Africa and important sources of income, especially in urban areas.In April 2009 diseased lettuce plants were first brought to Mobile Plant Clinics operating at Ouidah in the South of Bénin (Boa, 2009). Disease symptoms consisted of numerous foliar necrotic lesions, light brown circular with grey centres and purple margins, 0.3-0.6 mm in diameter. Leaves covered with necrotic lesions were swabbed with alcohol and sections (1 mm2) bordering the lesion perimeter were surface sterilised by immersing in bleach (1.2% available chlorine) for three minutes, rinsed in sterile distilled water, plated onto potato dextrose agar (PDA) and incubated at 25°C on the laboratory bench. Subculturing was performed every seven days onto PDA. In addition, infected leaves were swabbed with alcohol and then maintained on the laboratory bench out of direct sunlight at 25°C in humid chambers (autoclaved plastic bags). Leaves in bags and pure cultures sporulated to produce hyaline conidiophores that were short and unbranched and often in bundles although occasionally solitary with a black scar on the conidiogenous cell from where conidia were detached. Conidia were hyaline, septate with a black scar where previously attached to the conidiogenous cell. Conidia were 65-165 μm long and 4-5 μm wide. The morphological characteristics confirmed the identity of the fungus to be Cercospora beticola (syn. C. longissima)(Chupp, 1954; Crous & Braun, 2003). This description differs from that for Cercospora lactucae which has long dark brown conidiophores and much shorter conidia. The culture has been deposited at IITA under the reference no. 984.

Koch's postulates were satisfied by adding PDA plugs (0.5 mm2) from seven-day-old cultures of the recovered fungus onto lettuce leaves of three-week-old plants and covered with sterile moistened cotton wool for one day. Within 10 days the same characteristic symptoms were produced as those first observed on lettuce plants brought to Mobile Plant Clinics, from which Cercospora beticola was recovered into pure culture on PDA. C. beticola is primarily a pathogen of beet, but is also reported on other members of the Chenopodiaceae, as well as Amaranthus and lettuce. The disease significantly reduces production and the quality of lettuces produced and is currently distributed across the southern coastal areas of Bénin (from Porto Novo to Cotonou to Grand Popo) and as far North as Bohicon in central Bénin. No surveys have been undertaken further north (Yoro, 2009; James et al., 2010). This is the first report of C. beticola in Bénin.

Acknowledgements

Thanks are owed to International Plant Diagnostic Network for financial assistance (mediated through IPM-CRSP, USAID)


References

  1. Boa E, 2010. Plant Healthcare for poor farmers around the world: gathering demand and innovative responses. In: Plant Pathology in the 21st Century, vol. 4. Hardwick NV, Guillano M, eds. Berlin, Germany: Springer, 1-16. [http://dx.doi.org/10.1007/978-1-4020-8934-3_1]
  2. Chupp C, 1954. A monograph of the fungus genus Cercospora: 143. Ithaca, New York, USA (privately published).
  3. Crous PW, Braun U, 2003. Mycosphaerella and its anamorphs. 1. Names published in Cercospora and Passalora. CBS Biodiversity Series 1: 1-571. Utrecht, Netherlands: CBS/KNAW.
  4. James B, Atcha-Ahowé C, Godonou I, Baimey H, Goergen H, Sikirou R, Toko M, 2010. Integrated pest management in vegetable production: A guide for extension workers in West Africa. Ibadan, Nigeria: International Institute of Tropical Agriculture (IITA).
  5. Yoro B, 2009. Lutte chimique contre la maladie des taches foliaires de la laitue causée par Cercospora sp. Mémoire de licence en agronomie, Université Catholique de l'Afrique de l'Ouest (UCAO), 30p.

To cite this report: Hotegni Houessou JH, Beed F, Sikirou R, Ezin V, 2011. First report of Cercospora beticola on lettuce (Lactuca sativa) in Benin. New Disease Reports 23, 16. [http://dx.doi.org/10.5197/j.2044-0588.2011.023.016]

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