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Pteridophyte
DNA C-Values Database
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INTRODUCTION
The DNA amount in the unreplicated haploid or gametic
nucleus of an organism is referred to as its C-value (Swift 1950), irrespective
of the ploidy level of the taxon. C-value equals genome size in diploid
species, but always exceeds genome size in polyploid species. Nuclear
DNA C-value and genome size are important biodiversity characters with
fundamental biological significance and many uses (Bennett
and Leitch, 1995; Bennett
et
al., 2000). Estimates of nuclear DNA amounts are now available
electronically for c.1.4% of all angiosperm species in the Angiosperm
DNA C-values database.
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C-value data in pteridophytes
Given the broad and growing demand for information on plant DNA C-values,
it is clearly important to monitor what is known, and to recognise what
is unknown and needed most for other plant groups besides angiosperms (Bennett,
1998). A workshop and discussion meeting focussed on these
issues was held at the Royal Botanic Gardens, Kew (RBG, Kew) in September
1997, sponsored by Annals of Botany. This was attended by 86 scientists
from 15 countries with expertise in generating, or interest in using, information
on plant nuclear DNA amounts. Papers from the discussion meeting
were published in a special issue �Genome size in plants� in Annals
of Botany volume 82 (Supplement A; see Bennett and Leitch, 1998).
The workshop�s recommendations were reported orally to participants at
the meeting, and a summary is available on the web (see Angiosperm
Genome Size Discussion Meeting).
A key aim of the 1997 workshop was to identify major gaps in our knowledge
of plant DNA C-values and to recommend targets and priorities for new work
to fill them by international collaboration. Murray reviewed our
knowledge of C-values in non-angiosperm plants. A survey
of the literature indicated that C-value data were available for
only c. 0.42% of pteridophyte species and that the data were difficult
to locate. The workshop concluded that this level of ignorance
was unacceptable. New work targeted to improve representation
of this group was essential
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The need for a reference list of pteridophyte DNA C-values
Difficulties encountered in locating C-value data for pteridophytes
clearly demonstrated the value of user-friendly reference works.
Thus, there was a clear need to bring together DNA amount data for pteridophytes
and make them easily accessible in one pteridophyte DNA C-values
database. To address this Bennett and Leitch (2001) have pooled the
available estimates of pteridophyte DNA amounts into one user-friendly
reference source. This fulfilled an important recommendation of the
1997 workshop for this group.
In total, Bennett and Leitch (2001) listed DNA C-values
for only 48 pteridophyte species from eight original sources which highlighted
an ongoing need for work to increase knowledge in this area. Comparison
shows that the 1C-value estimates differ by at least 1000-fold, ranging
from a minimum of 0.055 pg for four
Selaginella species to a maximum
of about 55 pg in Ophioglossum petiolatum.
The layout of the table and the form of the associated
notes closely follows that of similar reference lists for angiosperms (e.g.
Bennett
et
al., 2000) and gymnosperms (Murray,
1998) both as an aid to users and to facilitate combining such lists
into a single plant DNA C-values database.
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The Pteridophyte DNA C-Values Database (release
1.0)
To make the estimates of C-values in pteridophytes
more widely available, the information given in Bennett and Leitch (2001)
has been made available electronically. This database gives 1C-values
in both pg and Mbp for 48 different pteridophyte species. Additional
information on spore type (i.e. homosporous or heterosporous), flagella
number (i.e. biflagellate or multiflagellate), sporangial type (i.e. euspsporangiate
or leptosporangiate), chromosome number and ploidy level are also
given where known .
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Updates
We plan to improve and develop the database.
REFERENCES
Bennett MD, Leitch IJ. 1995. Nuclear DNA
amounts in angiosperms. Annals of Botany 76: 113-176.
Bennett MD, Leitch IJ. 1998. Nuclear DNA
amounts in angiosperms - preface. Annals of Botany 82 (Supplement
A): 1
Bennett MD, Bhandol P, Leitch IJ. 2000.
Nuclear DNA amounts in angiosperms and their modern Uses � 807 new
estimates. Annals of Botany 86: 859-909.
Bennett MD, Leitch IJ. 2001. Nuclear
DNA amounts in pteridophytes. Annals of Botany 87:(in press).
Murray BG. 1998. Nuclear DNA
amounts in gymnosperms. Annals of Botany 82 (Supplement A):
3-15.
Swift H. 1950. The constancy of deoxyribose
nucleic acid in plant nuclei. Proceedings of the National Academy of
Sciences 36: 643-654.
Questions or comments/suggestions
regarding database content should be sent to
dnac-value@kew.org
Bug reports regarding this database
service should be sent to dnac-db@kew.org
©Copyright
(2000), Board of Trustees of the Royal Botanic Gardens, Kew