Microseris douglasii (DC.) Sch.-Bip. and M. bigelovii
(Gray) Sch.-Bip. are two small annual autogamous species of
Compositae with nearly non-overlapping distribution ranges in Western North
America. Specifically, M. bigelovii
occurs directly along the Pacific coast, whilst M. douglasii has
an inland distribution including patches of
serpentine soil. Both species are variable, and artificial hybrids between
them vary widely in fertility depending
on the individual parents. Segregating offspring of one hybrid (strain
H27) is
being used to analyse the genetic
basis of characters differentiating the two species by QTL mapping with
RAPDS and ALFPs as molecular
markers. Technical problems with mapping dominant markers in a wide cross
will be briefly listed and QTL
analysis will be discussed. For the genetic analysis of physiological
characters, the precise definition of the
characters is crucial and the methods of scoring or measuring phenotypes
in
different environments eventually
require more time and effort than the molecular characterization. We are
establishing recombinant inbred lines
to provide material for more complex physiological analyses requiring
several plants per genotype. An increasing
number of characters is being studied in this cross, and the possibility
of
shared pleiotropic QTLs is high. The
potential number of QTL genotypes by far exceeds the number of actual
genotypes in these lines. We are
characterizing the gene interactions as closely as possible and making
quantitative genetic models to predict the
genotypes corresponding to all possible genotypes. These predictions
are converted via computer modelling into
an increasingly realistic three-dimensional representation of the growing
plant useful for a simulation of plant evolution.