Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2005
Publication Date: 9/1/2005
Citation: Fisher, A.J., Gordon, T.R., Ditomaso, J.M. 2005. Conidia morphology and ecological characteristics as diagnostic tools for claviceps purpurea from salt marsh habitats. Canadian Journal of Plant Pathology.27:389-395.
Interpretive Summary: The ergot fungus is a pathogen that infects wildland grasses and agriculturally important cereal grains. Though a single species, it is composed of three distinct groups, and only one of these groups causes disease in agriculture. The groups within ergot can be differentiated using genetic tools, but this type of analysis is expensive and labor intensive. We have discovered that the type of ergot that infects wildland grasses can be differentiated from the type that infects cereal grains by spore morphology. These findings will allow us to determine which type of ergot is present without the use of genetic analysis.
Technical Abstract: Claviceps purpurea associated with grass hosts in salt marsh habitats, also known as G3 ergot, can be differentiated from C. purpurea infecting grasses in other habitats using genetic, chemical and morphological criteria. However, only morphological analysis can be used on herbarium specimens, which should not be destroyed or older samples that cannot be grown in culture. To determine if conidia characteristics could be used to identify sub-groups of C. purpurea (G1 – G3), isolates from terrestrial grasses (G1), moist habitats (G2) and salt marsh habitats (G3) were examined. All G1 sclerotia sank in water. All G3 sclerotia floated in water, except those from Washington. Group 2 sclerotia did not float in water, except those collected from Calamagrostis nutkaensis and Ammophila breviligulata. Based on the length of conidia derived from a plant host, G1 samples are indistinguishable from G2 samples but are significantly different from G3. Conidia produced in culture were on average smaller than conidia produced on plant hosts. These results indicate that ecological and morphological characteristics can be used to distinguish G3 from G1, but cannot consistently separate either from G2.