Two new species from dead wood, with an activity test

The family Didymosphaeriaceae belongs to the order Pleosporales and is distributed worldwide. Its members occur as saprotrophs, pathogens and endophytes of plants, and the group is flagged as promising for agricultural and medicinal applications.

The motivation for the study is explicitly practical. Because of the environmental risks posed by chemical pesticides, plant-associated microorganisms have become an important resource for developing eco-friendly biopesticides. That frames the taxonomic description not as an end in itself but as the first step in inventorying a resource.

Wenxiu Su's team collected decaying wood tissue in north-east China and examined it morphologically and phylogenetically, analysing five loci: ITS, SSU, LSU, tef1-α and rpb2. Two new species were described: Chromolaenicola crataegicola and Paraphaeosphaeria fulva.

What came next is the unusual part. The authors preliminarily assessed the antibacterial and antifungal activity of the secondary metabolites of both species. In taxonomic practice that combination is rare — describing a species and testing its bioactivity are usually separate papers, often by separate teams, years apart.

For readers of this site the result illustrates a principle worth repeating: fungal secondary metabolites are compounds a fungus does not need in order to grow, and which it makes in its dealings with other organisms. Penicillin, ciclosporin and the statins all came off that shelf. Every newly described saprotroph from dead wood is potentially another item on it — and until somebody describes it, it cannot even be studied.

The genus name itself carries an interesting history. Chromolaenicola was erected for fungi found on Chromolaena odorata, a plant in the daisy family that is a troublesome invasive across much of the tropics. The new species, however, bears the epithet crataegicola, pointing at hawthorn.

That mismatch between a genus name and a species host is common in mycology and can mislead. A genus is named after whatever it was first found on, not after its host range — which usually turns out to be wider the longer anyone looks.

What the paper establishes

Chromolaenicola crataegicola was described from a dead Crataegus branch and Paraphaeosphaeria fulva from unidentified dead wood in Jilin. Morphology was integrated with ITS, SSU, LSU, tef1-α and rpb2. Crude ethyl-acetate extracts at 20 mg/ml inhibited Staphylococcus aureus but not Escherichia coli; plate assays inhibited three fungi by about 76–89%, versus 100% for carbendazim. This is a screen of mixtures, not identification of an active compound or evidence of efficacy, safety or field performance as a biopesticide. The source also contains an inconsistency: type accounts link C. crataegicola to EMFCC 0089 and P. fulva to 0084, but methods reverse the culture numbers. Species-level attribution requires caution pending correction.