I am involved in studies regarding Agricultural Genetics. The
purpose of these studies is to determine genetic bases of traits
which can be useful in the frame of a sustainable agriculture.
These studies presently address mainly the understanding and the
exploitation of heterosis and of tolerance to stress.
My researches concern mainly one species, i.e., maize, which I
have chosen both because of its great economic importance and
because it is a well known model species for heterogamous
crops.
Methods utilized in my research are those of classical
quantitative genetics, combined with information coming from
molecular genetics and genomics by means of advanced statistical
tools.
Themes recently considered:
- Quantitative genetics
- Detection of loci controlling heterosis in maize
- Location of quantitative trait loci (QTL) in complex mapping
populations
- Characterization of isogenic lines for heterotic QTL in
maize
- Analysis of cold tolerance at germination in maize
A - MEHODS COMMOS TO DIFFERENT RESEARCH PROJECTS.
- Genetic markers for the identification of QTL (quantitative
trait loci) by means of the combination of phenotypic traits marker
data in segregating populations.
- Production of ad hoc genetic materials (i.e., segreagating
populations, cross of different stocks showing variability for
different traits).
- Development of Near Isogenic Lines (NILs) differing for a
particular genomic region of intertest.
B - RESULTS SO FAR OBTAINED.
- Heterosis, or hybrid vigour, refers to the superiority, in
biomass and fertility of a hybrid compared to its inbred parents.
Despite a century of investigations the genetic and the molecular
bases of heterosis are still unclear. In a recently published
research (Frascaroli et al. 2007), we addressed the genetic basis
of heterosis in the material developed from the cross between B73
and H99 maize inbred lines. This study revealed appreciable
heterosis for plant height and even a more marked heterosis for
early vigour, grain yield and its component number of kernels per
plant. The utilization of a suitable genetic design (a triple test
cross), together with QTL detection procedures, allowed us to
identify several QTL contributing to heterosis and to estimate
their principal mode of action. In our material, heterosis was
mainly due to allelic interaction (dominance at various levels),
with non-allelic interactions (epistasis) playing a less important
role. In a following research, we also studied stability of
heterotic QTL when crossed with related and unrelated tester lines
(Frascaroli et al., 2009). This study showed that, while QTL
additive effects are quite stable with different testers, non
additive QTL effects and especially overdominance can vary
substantially with different testers.
An important step to identify the relevant genes underlying a
QTL is the separation of the individual QTL from other segregating
loci. Such a Mendelization of a QTL can be achieved by constructing
near-isogenic lines (NILs), which can be characterized genetically.
For some of the detected heterotic QTL, we developed NILs pairs,
homozygous for contrasting alleles (Pea et al., 2009). NILs can be
replicated extensively to detect small effects and can be tested in
heterozygous combination by mating members of NIL pairs to each
other, to the related or to unrelated inbred lines. In particular,
crosses made among each couple of NILs and with the two parental
lines will provide unbiased estimates of both the additive and
dominance effects associated with the QTL. In case of crosses with
unrelated inbred lines it is possible to assess if QTL effects are
consistent in different genetic backgrounds. This information will
be of a great value for marker assisted selection (MAS), which is
efficient in case of QTL with stable effects. We already
preliminarily evaluated these materials in order to plan their
further extensive evaluation.
