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15. SUMMARY
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ses of insertional polymorphism fully confirmed the previous data that L. multiflorum and
L. perenne had the common gene pool and they can not be regarded as biological species.
However, the higher activity of transposons in L. multiflorum suggests further diversification
of both species. The association of distorted regions on genetic map of L. multiflorum
and L. perenne with transposons was another confirmation of their role in the early steps
of evolution of the genus Lolium.
Comparison of marker distortions in intra- and interspecific F 2
populations derived
from four different crosses and genetic mapping of 502 DNA, enzymatic markers and seedling
root fluorescence provided more evidences that a relatively little genetic incompatibilities
were between L. multiflorum and L. perenne and no signs of a reproductive barrier
were observed. The majority of markers segregated in the Mendelian fashion. The level of
distortions was comparable in intra- and interspecific crosses. Selection against transposon
insertion provided evidences that intraspecific mechanisms protecting from undesired
mobilisation of transposons are well working in the populations derived from crosses between
L. multiflorum and L. perenne. Moreover, seedling root fluorescence that is regarded
as marker discriminating L. multiflorum from L. perenne was found to be encoded by two
complementary genes located on LG1. In intra- and interspecific populations either both
genes or one of them can segregate. This model of inheritance explains well the difficulties
in species separation and stabilisation of the seedling root fluorescence level in cultivars of
these species frequently encountered by breeders.
There are no differences with respect to the occurrence, magnitude and mechanisms
underlying heterosis in inter- and intraspecific crosses. Heterosis resulted from dominance
and gene interactions and it was not correlated with genetic distance between parents.
In total 145 QTLs were responsible for L. multiflorum and L. perenne evolution however,
the majority of them were related with the process of domestication. According to historical
sources L. multiflorum is a domesticated form of L. perenne that was selected in the
Middle-Ages, and after that elevated to a species status. The domestication process is
controlled by many major QTLs in addition to several minor QTLs that are located within
nine domestication syndrome regions on six linkage groups. All these data fully confirmed
our previous view that L. multiflorum and L. perenne can not be regarded as biological species.
Therefore their taxonomic rank should be lowered and the subspecies level seems
to be more appropriate. Implementing the same philosophy as it is done for maize and
teosinte, or indica and japonica forms in rice, it was proposed to classify L. multiflorum and
L. perenne with a rank of subspecies i.e., L. perenne ssp. perenne for a more primitive form
and L. perenne ssp. multiflorum as a domesticated form in agreement with the Integrated
Taxonomic System of the USA.
Once the evolutionary relationships between L. multiflorum and L. perenne were resolved,
it was possible to clarify the phylogeny of the whole genus Lolium. At this point
plenty molecular methods were used to estimate the level of divergence between seven
species of the genus Lolium, L. loliaceum, L. persicum, L. remotum, L. temulentum,
L. multiflorum, L. perenne and L. rigidum. Moreover, closely related species, F. pratensis
and P. pratensis were used to help the tree rooting. No studies can be compared
with the present in the terms of number of methods and markers used to reliably establish
the evolutionary relationships within the genus Lolium. The restriction analysis of the