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8. MOLECULAR PHYLOGENY OF THE GENUS LOLIUM
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have indicated that the odd placement of one F. pratensis, greatly changes the tree. Moreover,
the polyphyletic structure of L. rigidum accessions has been shown. Thereby, Gaut et
al. (2000) concluded that the genus Lolium evolved from Schedonorus ancestor, of which
F. pratensis is a representative. This theory would explain why F. pratensis occupies the
position between groups of self-pollinated and out-pollinated species. The example includes
the tRNA tree, SSAP tree and random marker tree. Notably, transposon-based markers that
proved to be especially useful in phylogenetic studies in many plants, that elegantly resolve
evolutionary relationships of Pisum (Vershinin et al. 2003), that are the only markers showing
the early divergence of multiflorum from perenne, also indicate that the common ancestor is
more similar to F. pratensis. The same picture emerges from a wealth of random markers.
Hence, it is likely that the position of F. pratensis in the consensus tree is somehow disturbed
by low copy gene markers, although from strictly statistical point of view it seems impossible.
However, if the common ancestor had the closest affinity to F. pratensis, it is easier to explain
the similar time when auto- and allogamous species began to diverge. It is also easier to explain
the similarity between restriction patterns of the allergen encoding gene, LOLPISO5A
in F. pratensis and both L. remotum and L. temulentum. This possibility is supported by the
common cpDNA haplotypes between L. persicum and F. pratensis and completely different in
L. rigidum. If autogamous species evolved from a common ancestor similar to F. pratensis
then the haplotype of L. persicum originates from that ancestor. Under the above explanation
another problem arises. L. rigidum has different structure of the LOLPISO5A gene as
indicated by the lack of amplification products. Where does therefore, the gene in multiflorum
and perenne originate from A considerable body of data from breeding experiments has
proved the presence of gene flows between different taxa of the genus Lolium and Festuca
(Humphreys et al. 2003). Some Festulolium cultivars have been developed through crossing
multiflorum with F. pratensis or with F. arundinacea and perenne with F. pratensis and have
been introduced as novel temperate forage grasses in both Europe and the USA (Yamada
et al. 2005). Hence, one of L. perenne subspecies might inherit the gene through introgression
from Festuca. And because perenne and multiflorum are fully interfertile, the gene has
become widespread in both subspecies. There are more and more data about increasing
level of allergens in L. perenne (Sidoli et al. 1993) and the spontaneous as well as intended
crosses with Festuca are the most likely reason. All the more the higher winter hardiness and
disease resistance of Festuca make it an attractive component of crosses in many breeding
programs. This hypothesis is reasonable in the light of the facts that natural F. pratensis
x L. perenne hybrids are found throughout the British Isles and Northern Europe (Gaut et al.
2000).
To summarize, the more ancestral position of F. pratensis in comparison with
L. rigidum in the majority of trees results from two different processes. Firstly, it is a reminiscence
of past introgression accidents. Secondly, and more important, it mirrors the evolutionary
relationships and its position as a common ancestor to both Lolium clades. Under
this hypothesis, the divergence of the autogamous species from a common ancestor can
be dated to 2.7 MYA and then the split between allogamous Lolium species and Festuca
lineage can be postulated to 2.35 MYA. This theory inevitable entails the conclusion that
F. pratensis should be classified within the genus Lolium as it has been proposed by Craven
et al. (2005). Catalan et al. (2004) propose Schedonorus (broad leaved Festuca), of which