Archivos de diario de agosto 2022

26 de agosto de 2022

Uromyces aureus vs. Uromyces chlorogali

For some time, observations of a rust that occurs on Chlorogalum pomeridianum (Soap Plant) have been identified on iNat as Uromyces aureus. The common name for this species on iNat was even, up until today, designated as "Soap Plant rust". Contradicting the appropriateness of these identifications and the former common name designation is the fact that the original species description for U. aureus describes a rust that occurs on Allium validum - not C. pomeridianum. Additionally, the same two authors who described U. aureus separately described a rust that occurs on C. pomeridianum and named it Uromyces chlorogali - both descriptions being published in the same year! Given that rusts are host-specific parasites, it seems obvious that the rust that occurs on C. pomeridianum should be called U. chlorogali and the rust that occurs on A. validum should be called U. aureus - as they were both originally described. The assignment of the name U. aureus to the rust that occurs on C. pomeridianum seems to originate in confusion about the host preference of U. aureus. This confusion itself seems to originate from two sources: multiple herbarium specimens of the rust on C. pomeridianum that were labeled as U. aureus (Link 1), and a plant disease handbook that lists U. aureus as a known pathogen of C. pomeridianum (Link 2). I have found no literature that states that U. aureus occurs on both C. pomeridianum and A. validum. I think that the listing in the plant disease handbook of U. aureus as occurring on C. pomeridianum happened because the author was looking at herbarium specimens and did not attempt to reconcile the original species descriptions with the specimen labels. In the interest of being thorough, I think it's important to consider why these specimens may have been labeled as U. aureus. While it is well known that herbarium specimens are frequently incorrectly labeled - this case is puzzling as it seems to be an unlikely mistake. If the herbarium specimens were being identified based on macro and micro morphology alone, I can see why this mislabeling might have occurred, but from what I've gathered, morphology is not useful for species level identification in rusts. This is certainly true in the case of U. aureus and U. chlorogali, as they both have similar macro and micro morphology - to the point that host plant association is the only currently available and reliable way to distinguish between the two species (as per the original descriptions). It is surprising to think that biologists were depositing and labeling specimens at the species level without consideration of the host plant. Despite this apparent mislabeling seeming to be an unlikely and egregious error, it is the only explanation I can find for the use of the name U. aureus for the rust that occurs on C. pomeridianum. With no literature stating that U. aureus occurs on both C. pomeridianum and A. validum (that I could find), the tendency of rusts to be host specific, and the original species descriptions of both rusts only mentioning their occurrence on one host, I am confident that the rust occurring on C. pomeridianum should be identified as U. chlorogali. I am glad to see that the common name "Soap Plant rust" for U. aureus has been removed. Maybe next it should be changed to "Swamp Onion rust" and "Soap Plant rust" applied to U. chlorogali instead. Below I've linked to the original species descriptions for U. aureus (Link 3) and U. chlorogali (Link 4). I've also done microscopy for U. aureus (Link 5) and U. chlorogali (Link 6).


  3. U. aureus description in observation notes (translated from german):
  4. U. chlorogali description in observation images:
  5. U. aureus spore microscopy in observation images:
  6. U. chlorogali spore microscopy in observation images:
Publicado el agosto 26, 2022 11:21 TARDE por thehyphaemovement thehyphaemovement | 1 comentario | Deja un comentario