Joint International Conference on Long-term Experiments ...

DISCUSSION
The species level segregation of the two observed grass species is not supported by the
morphological features measured. Rua (1996) reported similar results, as the
quantitative morphological features did not reveal sharp statistical segregation between
some Poa species. In our study the basis of the identification was the width of the leaf
blades whilst other features, such as the length values, also used in identification keys,
did not prove to be useful.
Our previous observations suggested that the habitat adaptation, due to the habitat
variations, destroyed the sharp border in morphological features between the two
species. The results of the present study also supported that there was no phenotypic gap
between these species, based on the measured characteristics. After three years growing
in the same plot, tillers showed differences in morphological characteristics compared
to individuals of original habitats. In some cases it seems there are not correspondences
between morphological characters and genotypes (McElroy, et al. 2002; Gillespie and
Boles, 2001). These observations are consistent with the results of our study.
The present study confirms the previous results that behind the habitat-sensitive
features of grass shoots there is high within-species genetic variability. This could be
due to a relatively high proportion of potentially sexually produced off-types (Larson et
al., 2001; Curley and Jung, 2004). AFLP variation of population in Poa pratensis L.
aggregation does not show species level separation between the studied species based
on the generated AFLP markers. The Poa pratensis L. group serves as an example of
the fact that in cases of polymorphic taxa the genetic variability results in adaptation to
small environmental changes and that separable ecotypes exist. Thus, this study
provides further evidence for the utility of AFLP for turfgrass genetics as well as
important genetic information for turf breeders and managers.
Our study showed that the morphological plasticity of our species was
considerable, which was related to the small scale variability of the habitats. Thus, the
measured quantitative morphological characters were not useful for taxonomic
separation. There was no difference in the usefulness of the vegetative and generative
features considering for the separation of the species.
The study of AFLP variation of populations of the two species suggests complex
population structures with high levels of introgression. Such results are consistent with
the morphological variation seen in genera Poa generally. The high degree of
polymorphism in Eastern Hungarian populations resulted in continuous forms from
apparently pure P. humilis to apparently pure P. angustifolia. The transplantation
experiment showed that, despite considerable phenotypic plasticity, the morphology is
determined by genotype (Howland et al., 1995). Poa taxa have high genetic potential
for microevolutionary development.
REFERENCES
Bonos, S. A., Meyer, W. A., Murphy, J. A. (2000): Classification of Kentucky
bluegrass genotypes grown as spaces-plants. Hortscience 35 (5): 910-913.
Curley, J., Jung, G. (2004): RAPD-based genetic relationships in Kentucky bluegrass.
Crop Sciences 44: 1299-1306.
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