Description of Alternaria kierstenii sp. nov. from invasive garlic mustard highlights agricultural biosecurity risks of foreign weeds as pathogen reservoirs

Alternaria kierstenii sp. nov., isolated from diseased garlic mustard in Maryland, USA, has a near-chromosome genome assembly of 35.8 Mb and a highly aggressive Brassicaceae host range.

• Why it matters: Invasive weeds near farms can act as reservoirs for emerging or poorly characterized plant pathogens, but understudied weeds may hide pathogen diversity with agricultural consequences.
• What they did: The team sequenced a 35.8 Mb genome (17 contigs), compared it with other crucifer-infecting Alternaria, and used phylogenetics plus host-range assays to define taxonomy and aggressiveness.
• The result: The fungus caused foliar and stem lesions, chlorosis, necrosis, leaf death, and rapid mortality on multiple Brassicaceae hosts, and related taxa were detected only in eastern Maryland, Pennsylvania, and New York.

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