Proceedings of the XLV Italian
Society of Agricultural Genetics - SIGA Annual Congress
Salsomaggiore Terme, Italy - 26/29 September, 2001
ISBN 88-900622-1-5
Poster Abstract
A COMPARATIVE ANALYSIS OF POPULATION
STRUCTURE IN BARLEY LANDRACE POPULATIONS FROM SARDINIA, ITALY: I) GENETIC MARKERS AND
QUANTITATIVE GENETIC VARIATION; II) OVER-TIME ANALYSIS OF THE
GENETIC DIVERSITY
* Dipartimento di Biotecnologie
Agrarie ed Ambientali, Università degli Studi di Ancona, Ancona, Italy
** Dipartimento di Scienze
Agronomiche e Genetica Vegetale Agraria, Università degli Studi di
Sassari, Sassari, Italy
In the last
years the role of "in situ" conservation of
domesticated plant populations has been revaluated as an important strategy for
preserving crop genetic resources as an adjunct to conservation in "ex
situ".
As a consequence the interest on
the population dynamics of landraces in order to implement such
conservation strategy increased.
Molecular markers are generally
assumed neutral so that they
mainly reflect the effect of random genetic drift and migration. Their
departure from neutral expectation is considered related to linkage with loci
under selection: hitchhiking or background selection. The comparison between
neutral molecular markers and quantitative traits or more generally selective
markers is a powerful tool in order to dissect the role of different
evolutionary forces on the shaping of genetic diversity. We used this
approach to address the question whether genetic differentiation between
landraces population is due to drift alone or also to selection.
The genetic structure of barley landrace was compared
between 18 genetic markers (13 RAPD markers, 3 morpho-phenological traits and 2
isozyme loci) and 22 quantitative
traits.
Data were analysed by a hierarchical analysis of
variance for quantitative traits and genetic marker data were analysed
according to a hierarchical analysis of molecular variance for haploid data.
For both the effect of regions, populations and genotypes were considered
Confidence
interval (P<0.05) of the average values of variance components were obtained
by bootstrapping over characters and markers. Bootstrapping over individuals
within populations was used to estimate the confidence intervals of single
markers or traits.
Quantitative traits showed an overall significantly
higher differentiation for all level of structure when compared to genetic
markers, moreover a significant difference was observed for the genetic
structure of different traits. These results indicated that landrace
populations were differentiated by heterogeneous selection among different
environment and that recombination plays an important role in spite of the
strict selfing nature of barley.
We have also analysed the evolution over-time of
these populations by comparing the genetic diversity (ISSR and SSR) of
populations collected in 1990 with populations collected in 2000. From the
molecular data the level and the structure of diversity did not significantly
differ over time. The metapopulation structure and the role of the different
evolutionary forces on the maintenance of the genetic diversity in landrace
populations is discussed.