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A Novel Subspecies of Didymella acutilobae Causing Leaf Spot in East Asian Hogweed

Summary

Researchers identified a new fungal disease affecting East Asian hogweed, an edible herb used in traditional medicine. The disease, called leaf spot, was caused by a previously unknown subspecies of fungus named Didymella acutilobae subsp. heraclei. Using genetic analysis and laboratory testing, scientists confirmed this fungus is responsible for infecting hogweed plants in Korean fields. Understanding this pathogen is important for protecting this valuable medicinal plant.

Background

East Asian hogweed (Heracleum moellendorffii) is a perennial plant used as an edible herb with known anti-inflammatory and immune-enhancing properties. During disease surveys in 2021-2022 in Korea, leaf spot outbreaks were observed affecting 2-50% of plants in affected fields. The disease was caused by fungal isolates that were initially identified as Phoma species.

Objective

To characterize and identify fungal isolates causing leaf spot disease in East Asian hogweed plants using morphological, cultural, and molecular phylogenetic approaches. To determine if the isolates represent a novel species or subspecies within the Didymella genus.

Results

Phylogenetic analyses confirmed the isolates clustered closely with Didymella acutilobae but exhibited distinct morphological and cultural differences including longer conidia, more guttules, different colony colors, and faster growth rates. Pathogenicity tests confirmed all three tested isolates caused leaf spot symptoms on inoculated plants, with induced lesions resembling those observed in surveyed fields.

Conclusion

The isolates are designated as Didymella acutilobae subsp. heraclei, a novel subspecies distinct from D. acutilobae. This is the first report of D. acutilobae subsp. heraclei causing leaf spot disease in East Asian hogweed, representing an important fungal pathogen for this economically important plant species.
  • Published in:Mycobiology,
  • Study Type:Descriptive/Taxonomic Study,
  • Source: PMID: 39845182
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