Detection of the Phoma pathogens Plenodomus biglobosus subclades ‘brassicae’ and ‘canadensis’ on wasabi, and ‘canadensis’ in Europe

A - Papers appearing in refereed journals

King, K. M. and West, J. S. 2021. Detection of the Phoma pathogens Plenodomus biglobosus subclades ‘brassicae’ and ‘canadensis’ on wasabi, and ‘canadensis’ in Europe. European Journal of Plant Pathology.

AuthorsKing, K. M. and West, J. S.

Phoma stem canker / Blackleg is an internationally important disease of Brassicas including B. napus (oilseed rape, OSR), caused by multiple genetic subclades of the fungi Plenodomus lingam (formerly Leptosphaeria maculans) and P. biglobosus (L. biglobosa). In Spring 2021, Phoma-like disease symptoms were observed on leaves and stems of Eutrema japonicum (wasabi) crops at three UK sites (Northern Ireland, Southern England and the West Midlands). Fungal isolation from wasabi leaf spots yielded colonies with two distinct phenotypes on potato dextrose agar (PDA). Isolates from the Northern Ireland and Southern England sites had white colonies with abundant pink cirri that were confirmed (based on ITS rDNA, beta tubulin and actin sequences) as P. biglobosus subclade ‘canadensis’ (Pbc). Those from the West Midlands site, however, had yellow pigmented colonies and were confirmed by sequencing as P. biglobosus subclade ‘brassicae’ (Pbb). Greenhouse pathogenicity testing showed that Pbb and Pbc wasabi isolates were pathogenic not only to this host but also OSR, B. oleracea (cabbage), and B. rapa (pak choi). Re-isolation of the fungi was attempted and confirmed from lesions that developed on inoculated OSR and wasabi, thus completing Koch’s postulates. These findings represent first reports of both Pbb and Pbc on wasabi, plus of Pbc in Europe. The crop health implications of these findings are briefly considered.

KeywordsPlenodomus biglobosus; Subclade; New host; New Geography; Blackleg; Brassica; Leptosphaeria spp.; Phoma; Plenodomus spp.
Year of Publication2021
JournalEuropean Journal of Plant Pathology
Digital Object Identifier (DOI)
Open accessPublished as ‘gold’ (paid) open access
FunderBBSRC Industrial Strategy Challenge
Department of Environment, Food and Rural Affairs
Funder project or codeSmart Crop Protection WP1
Publisher's version
Accepted author manuscript
Supplemental file
Output statusPublished
Publication dates
Online02 Dec 2021
Publication process dates
Accepted22 Nov 2021

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