Aim : Preliminary results obtained with isozymes in
Q. petraea have shown that there is a geographic trend of
variation in the level of allelic richness : populations of the
central part of the natural distribution (from the Loire to the
Rhine) are less variable than populations from the peripheral
parts of the distribution. On the other hand Q. petraea
is more variable than Q. robur. Knowledge of the levels
of diversity in different species and different populations is
of primary importance for conservation strategies. The objective
is to evaluate the level of diversity in the two species and its
geographic variation, by sampling large size populations and using
hypervariable markers (exhibiting numerous alleles).
Subtask 3.1 Sampling of populations
| Pairs of populations of Q. petraea and Q. robur will be identified and selected for estimating gene diversity. The two populations of a pair should be in adult stands in close proximity with some mixed zones. Taxonomic identification will be made with leaf morphological characters. Populations size should be about 200 so that allelic richness can be measured. Trees will be mapped. Buds or leaves will be collected for DNA and allozyme analysis. |
Subtask 3.2. Standardization of molecular techniques for analysis
of nuclear polymorphism
| Techniques to monitor diversity will be shared during a two weeks technical meeting. These concern codominant markers allowing to identify the different alleles present in the populations: allozymes, microsatellites, PCR-SSCP fragments. Methods have already been developped for 13 enzyme-coding loci, and primers are available for 5 microsatellite loci, and 5 PCR-SSCP loci. Whereas, isozymes and microsatellites are anonymous markers, the PCR-SSCP fragments are specifically involved in the species differentiation. |
Subtask 3.3 Estimation of levels and structure of diversity
| The analysis of codominant markers in the sampled pairs of population will be conducted to:
- estimate the level of diversity in each population and species, by assessing the number of alleles, and expected heterozygosity.
- estimate the level of species differentiation by comparing allelic frequencies between the two species in each pair
- depict the within population structure of diversity by describing the spatial distribution of alleles. - describe the overall interspecific and geographic organisation of diversity by a joint analysis of allele frequencies over all pairs. |
Subtask 3.4 Estimation of genetic variation of phenotypic traits
| Subtask 3.4 is hypothetical, in the sense that it depends on the seed crop produced during the project. If there is a successfull seed crop, open pollinated progenies will be collect on at least 60 trees per population and raised in the nursery. Assessments of juvenile characters (phenology, morphological traits) will permit to estimate the level of diversity for quantitative traits. These levels will be compared with those obtained with codominant markers (Subtask 3.3). |
Table 3. Distribution of activities in Task 3