Diversity of microorganisms associated with atypical superficial blemishes of potato tubers and pathogenicity assessment |
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| Authors: | Marie Fiers Catherine Chatot Véronique Edel-Hermann Yves Le Hingrat Abel Yanougo Konate Nadine Gautheron Emmanuel Guillery Claude Alabouvette Christian Steinberg |
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| Institution: | 1.INRA, Université de Bourgogne UMR 1229 Microbiologie du Sol et de l’Environnement, CMSE,Dijon cedex,France;2.Germicopa R&D,Chateauneuf du Faou,France;3.Bretagne Plants,Hanvec,France;4.FNPPPT,Hanvec,France |
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| Abstract: | Skin blemishes of potato (Solanum tuberosum L.) tubers can cause severe economical losses to production. Some blemishes are due to known pathogens and others whose causes
are unknown are called atypical blemishes. The present work aims at determining the origin of superficial atypical blemishes
on a set of 204 tubers coming from 12 different French regions producing potato. The diversity of fungi and Streptomyces bacteria associated with blemishes was investigated by systematic isolation followed by identification by sequencing the
internal transcribed spacer of the ribosomal DNA for fungi and by sequencing the 16S ribosomal DNA for bacteria. We found
a high microbial diversity represented by 349 fungal isolates belonging to at least 47 different species and 21 bacterial
strains of Streptomyces sp. The most represented fungi belonged to the genera Fusarium, Rhizoctonia, Alternaria, Penicillium, and Clonostachys. The pathogenicity of representative isolates was assessed in three bioassays; two bioassays based on single inoculations
in previously sterilized potting mixture, and one bioassay based on both single and double inoculations under hydroponic conditions.
We fulfilled the Koch’s postulates for Rhizoctonia solani AG 3 producing sclerotia. For other fungal and bacterial strains, our results did not show any causality or relationship
between a single isolate or a complex and the occurrence of the blemishes. Moreover, the observation of irregular polygonal
sunken corky lesions (polygonal lesions)—the most frequent atypical blemish—on non-inoculated tubers, suggested that the atypical
blemishes could as well be a reaction of the plant to stressful environmental conditions. |
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