Submitted to: Mycological Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/20/2004
Publication Date: 4/1/2005
Citation: Fisher, A.J., Gordon, T.R., Ditomaso, J.M. 2005. Geographic distribution and diversity in claviceps purpurea (fr.) tul from salt marsh habitats and characterization of pacific coast populations. Mycological Research. 109:439-446. Interpretive Summary: Ergot is a well known fungal pathogen of cereal grains that also infects wild grasses. Though one species, this fungus can be separated into three discrete groups, and one of these groups occurs exclusively in coastal salt marshes. Salt marsh ergot has reached epidemic levels of infection in Spartina marsh grass in coastal Europe and the Atlantic Coast of the United States, but we know very little about its global distribution and how different it is from ergot in agricultural crops. Our research shows that the ergot found in salt marshes is genetically different from the ergot infecting rye, wheat and other cereal grains. Ergot found in salt marshes has a very limited host range, which includes only a few closely related grass species. Importantly, ergot of salt marshes has a global distribution, so it is not a new or emerging disease. Because of these traits, it is unlikely to pose a threat to agriculture and it is probably a natural component of coastal salt marsh habitats.
Technical Abstract: Claviceps purpurea that is specific to grasses in salt marsh habitats (G3) has previously been identified on Spartina spp. in two locations: New Jersey, USA and Southern England. We have identified G3 in 11 distinct populations including Western Europe, South America, and along the Atlantic and Pacific Coasts of the USA. Analyses of amplified fragment length polymorphism (AFLP) and random amplified polymorphic DNA (RAPD) data reveal distinct structure in G3 C. purpurea populations. Pacific Coast populations show little diversity, suggesting they may have been introduced recently in that region. All isolates originating from Spartina densiflora, S. foliosa, S. alterniflora, and S. anglica were identified as belonging to G3. In addition, G3 C. purpurea was discovered on a new host grass genus, Distichlis. RAPD and AFLP analyses supported the recognition of three discrete groups within C. purpurea and revealed high genetic variability between groups, with only 1.8% of polymorphic markers shared across all isolates. Similarly, analysis of molecular variation (AMOVA) revealed that genetic variability was mainly due to variations between groups, rather than within groups, or within populations. In conclusion, G3 C. purpurea has a global distribution and is probably a natural component of coastal salt marsh habitats.