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Results and discussion
The accessions proved to be highly variable for many of the
characters. However, all accessions had red seeds and short,
hook-like glume hairs. Other characters for which there was little
variation included awn colour, brittle rachis, spike density, seed
shape and the upper glume apex. All accessions had purple awns except
for one with yellow awns and all but one had a brittle rachis. Three
of the characters displayed a bimodal distribution in which a small
number of accessions were clearly distinct. Stripe rust infection was
severe on all but seven of the accessions and stem curvature was
prominent on only four accessions. The calculated rachis segment
length was derived from spike length divided by spikelet number. Most
of the accessions gave lengths below 9.5mm but six accessions stood
out with lengths of 1Omm or more. Results for all the measured
characters are summarized below in Table
1.
The descriptions given by Eig (1929) were used to identify different
subspecies and varieties within the collection. The subspecies
strangulata proved easy to identify; the glumes being only as
long as they are broad, in contrast to the more elongated glumes of
ssp. eusquarrosa. Dividing ssp. eusquarrosa into three
varieties proved to be more difficult. The variety anathera
is easily distinguished by the lack of all but terminal awns on
the spike. The other two varieties are divided on dimensions of the
spike with var. typica having thick spikes over 3.5mm wide and
var. meyeri having slender spikes less than 3mm wide. Several
accessions had spikes that were 3mm to 3.5mm thick, making it
difficult to positively identify them at this level but, despite
these problems, identifications were made so that the results could
be compared by multivariate analysis of the morphological data. Five
ssp. strangulata, fourteen ssp. eusquarrosa var.
anathera, 27 ssp. eusquarrosa var. typica and
eight ssp. eusquarrosa var. meyeri accessions were identified within
the collection.
Discriminant analysis was carried out to see if the different
subspecies and varieties of Ae. tauschii were well defined and
to explore the relationships between them. Results of the first test
(Table 2) demonstrate how well the
subspecies and varieties describe morphological variability within
the species. The results show that 44 out of the 54 accessions can be
correctly identified according to the characters used in the
analysis. This suggests that the subspecies and varieties can be used
to describe morphological variability between the accessions fairly
well but not completely accurately. The separation of ssp.
strangulata seems to be the most well defined division; none
of them were found to be misclassified by the analysis and no other
accessions were reclassified as ssp. strangulata. The
divisions within ssp. eusquarrosa were less well defined.
Relationships between the different subspecies and varieties can be
discerned from the squared distances between them (Table
3). All of the squared distances between ssp. strangulata
and the ssp. eusquarrosa divisions were over 35 suggesting
that ssp. strangulata is clearly distinct. In contrast, the
squared distance between varieties meyeri and typica is
only 2.19 suggesting that these varieties are morphologically very
close. Many of the accessions that stood out for stripe rust
resistance, stem curvature and distance between spikelets proved to
be ssp. strangulata. Other characters that could help to
define each subspecies and variety were discerned by comparing
character scores for accessions within each division. Some of these
are contrasted in Table 4 and suggest that
plant height, stem curvature, awn type, seed weight and seed shape
are the most useful characters for distinguishing the four divisions.
Differences in plant height and seed weight were confirmed as
significant by a Kruskal-Wallis test (height p<0.001, seed weight
p = 0.012).
Many species exhibit intraspecific variation and it can often be
important to express this in some way (Stace 1989). The descriptions
given by Eig (1929) have been widely used to identify the subspecies
strangulata and the varieties typica, meyeri and
anathera but how well do these describe morphological
variation within Ae. tauschii? This study utilized a
relatively small number of accessions but both subspecific and
varietal divisions were evident, affording an opportunity to assess
how robust these divisions are.
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