Transcript 2005.bsa meeting talk

Identifying host plants
of Hyobanche L.
(Orobanchaceae) by
DNA sequencing of
host root tissue
Andrea D. Wolfe and
Nidia Arguedas
The Ohio State University
Background on Hyobanche
• Small genus of holoparasitic plants endemic
to southern Africa
– Eight species described as of 1996
• One not seen in herbarium collections; three to be
submerged into one spp
– Another seven to be described
• Host plants noted on herbarium sheets
– Asteraceae, Ericaceae, Euphorbiaceae, Poaceae,
Restionaceae, Sterculiaceae, Thymelaeaceae
sp. nov.
sp. interm.
sanguinea
atropurpurea.
Background on Hyobanche
• Small genus of holoparasitic plants endemic
to southern Africa
– Eight species described as of 1996
• One not seen in herbarium collections; three to be
submerged into one spp
– Another seven to be described
• Host plants noted on herbarium sheets
– Asteraceae, Ericaceae, Euphorbiaceae, Poaceae,
Restionaceae, Sterculiaceae, Thymelaeaceae
Usually based on
proximity. . .
which may or
may not have
anything to do
with the actual
host plant!
Rhizomes of
Hyobanche may
be several meters
long, and host
roots are attached
along the length
of the rhizome on
specialized
haustoria from
leaf bracts.
Haustorial connections
are generally fragile,
which makes tracing the
host-parasite attachment
difficult.
Fynbos
Coastal habitats
Karoo
High Veld
Methods
• Excavate rhizome system of Hyobanche
• Collect roots attached via haustorial
connections
• Collect leaf tissue of plants in vicinity
• Sequence ITS and rbcL from roots and
leaves
– Matching sequence infers host of Hyobanche
Conclusions
• DNA “fingerprinting” approach works well
for identifying hosts of Hyobanche
– Positive identifications made for every
population sampled
• Host range of coastal populations primarily
in Asteraceae
– Also found on Passerina and Bromus
Acknowledgments
Field Assistance: Brad Ripley, Tony Dold, Beyers Cronje
Funding: National Science Foundation