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5. ORIGIN OF SEEDLING...
Perhaps in cooler environments, to which L. perenne is adapted, the effect of herbivory is
not so strong. Because the benefits related to alkaloid-mediated reduction of competition or
herbivory are not realized, the costs of alkaloid production are limited (Faeth 2002). This explanation
seems also plausible for L. persicum. This species is a noxious weed of oat that is
known from allellopatric properties. As a weed it can take advantage from the host alkaloids
not bearing any costs. A serious difficulty in all explanations of fluorescence in the genus Lolium
is unknown physiological role of annuloline. Its structure is clearly different from perloline,
it is only sparingly soluble in water (Axelrod and Belzile 1958) and presumably it does not act
as an osmoregulator. However, cinnamic acid, the parent compound of annuloline can act as
optical filters by blocking UV-A and B (“Cinnamic acid”, 2006). Perhaps UV light penetrating
soil layers could photoactivate fluorescent annuloine to create a defence response. To cite
one example, it is documented that insecticidal activity of fluorescent alkaloids secreted by
Oxalis tuberosa (oca) is linked to photoactivation. The strongest fluorescence is correlated
with resistance to the larvae of Mycrorypes and it is observed in cultivars from the Andean
highlands, which are subjected to a high incidence of UV radiation (Walker et al. 2003).
Regardless fluorescence is a species specific marker or not, it enables to distinguish
between two different functional types i.e., between annual, fast growing Italian ryegrass
and perennial ryegrass. And despite of variation in the fluorescence test it can be used as
a determinant trait in seed certification schemes to track mechanical seed contamination. Because
the majority of L. perenne plants do not fluoresce, the elimination of fluorescent seeds,
irrespective they are L. perenne or L. multiflorum assures that none undesirable plant will be
in a seed sample. This can be a pragmatic way to prevent from low turf quality. However, the
more basic way to distinguish crops or even cultivars is to identify DNA fragments or genes
that are responsible for differences. The three RAPD markers identified in the present work
and associated with fluorescence can be beneficial to developing such DNA tests. These
tests may reduce the problems caused by environmental variation and subjectivity in scoring
results. A striking example of a DNA marker used in separation of different phenotypes is the
SSR marker, sat309 located only 1-2 cM away from the rhg1 responsible for the resistance to
soybean cyst nematode. Genotypic selection with this marker is 99% accurate in predicting
susceptible lines (Babu et al. 2004). The other successful cases include two RAPD markers
tightly linked to a gall midge resistance gene (Gm2) in rice (Nair et al. 1995), two RAPD
markers flanking the locus Lr19 responsible for the leaf rust resistance in wheat (Gupta et al.
2006) and several markers based on single nucleotide polymorphism of coding and adjacent
noncoding regions of Pm3 alleles conferring resistance to powdery mildew in wheat, Triticum
aestivum and spelt, T. spelta (Tommasini et al. 2006). RAPD markers found in the present
work offer a quick and easy way of discrimination between L. multiflorum and L. perenne.
Nonetheless, they suffer some of the same problems as the seedling root fluorescence e.g.,
they are not valid for all cultivars. Much more accurate and flexible test can be developed
provided that DNA markers linked to key morphological characteristics are identified. There
are some morphological characteristics that differentiate L. multiflorum and L. perenne such
as the 1 st year ear emergence and recovery after winter (Chapter 3). Based on the knowledge
about the chromosome locations of QTLs underlying these characters far more DNA tests
can be developed.