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7. ROLE OF QTLs IN THE EARLY EVOLUTION...
QTLs responsible for basal leaf width and area as well as growth type had negative additive
effect and they were accumulated in one parent whereas minor QTLs had positive additive
effects and they were accumulated in the other parent.
The additive effects were unlikely to explain all of the variation observed. Particularly that
the large dominance effects were demonstrated for the majority of QTLs. Similarly to additivity,
if all QTLs were taken together, dominant genes with a positive influence on phenotypes
were dispersed between parents as indicating by different signs of the QTLs controlling the
same trait. In comparison with additive effects, dominant QTLs, both major and minor were
more frequently dispersed between parents. In addition to crown rust resistance and dry
weight of tillers, the other four characters including green weight of tillers, spikelet number,
flag leaf width and days to ear emergence were controlled by such QTLs. For several traits
only minor QTLs were dispersed. Examples involved minor QTLs with positive influence on
phenotypes that originated either from L. multiflorum or L. perenne and controlled length of
basal leaf, dry weight, growth type, and the presence of awns. The opposite relationship
i.e., dispersion of dominant major QTLs and association of minor ones was rarely observed.
However, a cautionary point to these considerations should be made. The fact that sum of
estimated magnitudes for some QTLs exceeded 100% suggested that QTLs did not act
independently of each other and epistatic interactions controlled at least some of analysed
characters.