Proceedings of the Third International Conference on Invasive ...

<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive SpartinaChapter 1: Spartina BiologyIS ERGOT A NATURAL COMPONENT OF SPARTINA MARSHES?DISTRIBUTION ANDECOLOGICAL HOST RANGE OF SALT MARSH CLAVICEPS PURPUREAA.J. FISHERDepartment <strong>of</strong> Plant Pathology, University <strong>of</strong> California, Davis, One Shields Ave., Davis, CA 95616; alijfisher@gmail.comThis study was undertaken to better characterize <strong>the</strong> geographic distribution and host range <strong>of</strong>Claviceps purpurea from grass hosts in salt marsh habitats. Claviceps purpurea contains threeintraspecific groups, each with a habitat association: G1 from terrestrial habitats, G2 from moisthabitats and G3 from salt marshes. Twenty-six G3 isolates, representing 11 distinct populationswere characterized based on <strong>the</strong> presence <strong>of</strong> an EcoRI restriction site in <strong>the</strong> 5.8S ribosomal DNA,and genetic similarity to isolates representing <strong>the</strong> o<strong>the</strong>r two C. purpurea intraspecific groups (G1and G2). Distichlis spicata was identified as <strong>the</strong> first non-Spartina host to G3 C. purpurea. Inaddition, all isolates originating from Spartina densiflora, S. foliosa, S. alterniflora, and S. anglicawere identified as belonging to G3 based on genetic analysis. Salt marsh Claviceps purpurea can befound along <strong>the</strong> Atlantic and Pacific Coasts <strong>of</strong> North America, Argentina, Ireland and England. Aglobal distribution suggests that salt marsh (G3) C. purpurea is a natural component <strong>of</strong> Spartinadominatedsalt marsh habitats.Keywords: Ergot, Claviceps purpurea, Spartina, host rangeINTRODUCTIONClaviceps purpurea (Fr.) Tul, <strong>the</strong> cause <strong>of</strong> ergot, is awell known pathogen <strong>of</strong> cereal grains and forage. Thepathogen has a global distribution, and a wide host rangewithin <strong>the</strong> Poaceae. This broad host range has led manyresearchers to seek evidence <strong>of</strong> taxonomic substructurebased on morphology (Loveless 1971), alkaloid production(Eleuterius and Meyers 1977; Kobel and Sanglier 1978), andgenetic characteristics (Jungehülsing and Tudzynski 1997).In a recent study, Pazoutová et al. (2000) syn<strong>the</strong>sizedprevious research on C. purpurea morphology, alkaloidchemistry and genetics, and identified three distinct groupswithin <strong>the</strong> species. Ra<strong>the</strong>r than divisions based on hostrange, <strong>the</strong> groups were defined by habitat association. Thelargest group, G1, was associated with terrestrial grasses,and G2 with grasses in moist environments, whereas G3 wasfound only in salt marsh habitats. Isolates associated withG1 and G3 share an EcoRI restriction site in <strong>the</strong> 5.8Sribosomal DNA (rDNA), which G2 isolates lack. The threegroups can be differentiated by RAPD analysis as well(Pazoutová et al. 2000).The ecological host range <strong>of</strong> maritime C. purpurea (G3)appears very narrow, compared to G1 and G2. G3 has beenisolated exclusively from cordgrass species <strong>of</strong> <strong>the</strong> genusSpartina. Two host species to G3 have been identified, eachin only one location: common cordgrass, S. anglica, in <strong>the</strong>United Kingdom and smooth cordgrass, S. alterniflora, from<strong>the</strong> state <strong>of</strong> New Jersey on <strong>the</strong> Atlantic coast <strong>of</strong> <strong>the</strong> UnitedStates (Pazoutová et al. 2000, 2002b).Whereas only two populations <strong>of</strong> G3 have beenidentified using molecular markers, <strong>the</strong> host to thisintraspecific group, Spartina, is a widespread genusincluding both terrestrial and halophytic salt marsh species.Most members <strong>of</strong> <strong>the</strong> genus, including S. alterniflora, sharea common native geographic range along <strong>the</strong> Atlantic Coast<strong>of</strong> North and South America. Introduced populations <strong>of</strong> S.alterniflora have established on <strong>the</strong> Pacific Coast as well, in<strong>the</strong> San Francisco Bay, California (Daehler and Strong 1994)and Willapa Bay, Washington (Stiller and Denton 1995).Thus, <strong>the</strong> geographic range <strong>of</strong> G3 may be much greater thanis presently recognized and it is reasonable to think thatdiversity in populations <strong>of</strong> <strong>the</strong> pathogen may reflect <strong>the</strong>diversity <strong>of</strong> <strong>the</strong> host species. The objectives <strong>of</strong> this studywere to assess <strong>the</strong> geographic distribution and ecologicalhost range <strong>of</strong> G3 C. purpurea.MATERIALS AND METHODSIsolates included in this study, and <strong>the</strong>ir origins, arelisted in Table 1. Isolates were sterilized and culturedaccording to <strong>the</strong> methods described in Pazoutová et al.(2000). Isolates not collected in <strong>the</strong> field were obtained aspure cultures from S. Pazoutová, including G1 isolates 374and 428 (Pazoutová et al. 2000), G2 isolates 236 and 434(Pazoutová et al. 2000), G3 isolates 500 and 538 (Pazoutováet al. 2002b), and G1 isolates165, 204 and 478. DNA wasextracted, and RAPD and AFLP markers were developedaccording to <strong>the</strong> methods described in Pazoutová et al.(2000). EcoRI analysis was also performed using <strong>the</strong>methods described in Pazoutová et al. (2000). Allmonomorphic and polymorphic RAPD and AFLP markerswere scored using a binary system (zero = absent and one =present). Percent similarity between isolates was calculatedby dividing <strong>the</strong> number <strong>of</strong> shared markers by <strong>the</strong> totalnumber <strong>of</strong> markers and multiplying by 100.-43-