Contrasting relationships between the diversity of candidate genes and variation of bud burst in natural and segregating populations of European oaks.

Nucleotide diversity was assessed within nine candidate genes (CGs) (in total 4.6 kb) for the time of bud burst in nine sessile oak (Quercus petraea) populations distributed in central and northern Europe. The sampled populations were selected on the basis of their contrasting times of bud burst observed in common garden experiments (provenance tests). The CGs were selected according to their expression profiles during the transition from quiescent to developing buds and/or their functional role in model plants. The overall nucleotide diversity was large (pi(tot)=6.15 x 10(-3); pi(silent)=11.2 x 10(-3)), but population differentiation was not larger than for microsatellites. No outlier single-nucleotide polymorphism (SNP) departing from neutral expectation was found among the total of 125 SNPs. These results contrasted markedly with the significant associations that were observed between the CGs and bud burst in segregating populations. Quantitative trait loci (QTLs) for bud burst were identified for 13 year*site seasonal observations in a cloned mapping pedigree. Nineteen QTLs were detected, and QTLs located on linkage groups 2, 5 and 9 contributed repeatedly to more than 12% of the phenotypic variation of the trait. Eight genes were polymorphic in the two parents of the pedigree and could be mapped on the existing genetic map. Five of them located within the confidence intervals of QTLs for bud burst. Interestingly, four of them located within the three QTLs exhibiting the largest contributions to bud burst.

Contrasting relations between diversity of candidate genes and variation of bud burst in natural and segregating populations of European oaks.

Nucleotide diversity was assessed within nine candidate genes (in total 4.6 kb) for the time of bud burst in nine sessile oak (Quercus petraea) populations distributed in central and northern Europe. The sampled populations were selected on the basis of their contrasting time of bud burst observed in common garden experiments (provenance tests). The candidate genes were selected according to their expression profiles during the transition from quiescent to developing buds and/or their functional role in model plants. The overall nucleotide diversity was large (π(tot)=6.15 × 10(-3); π(silent)=11.2 × 10(-3)), but population differentiation was not larger than for microsatellites. No outlier single-nucleotide polymorphism (SNP), departing from neutral expectation, was found among the total of 125 SNPs. These results contrasted markedly with the significant associations that were observed between the candidate genes and bud burst in segregating populations. Quantitative trait loci (QTLs) for bud burst were identified for 13 year*site seasonal observations in a cloned mapping pedigree. Nineteen QTLs were detected, and QTLs located on linkage groups 2, 5 and 9 contributed repeatedly to more than 12% of the phenotypic variation of the trait. Eight genes were polymorphic in the two parents of the pedigree and could be mapped on the existing genetic map. Five of them located within the confidence intervals of QTLs for bud burst. Interestingly, four of them located within the three QTLs exhibiting the largest contributions to bud burst.

Comparative mapping between quercus and castanea using simple-sequence repeats (SSRs).

Simple sequence repeat (SSR) markers from Quercus and Castanea were used for comparative mapping between Quercus robur (L.) and Castanea sativa (Mill.). We tested the transferability of SSRs developed in Quercus to Castanea and vice-versa. In total, 47% (25) of the Quercus SSRs and 63% (19) of the Castanea SSRs showed a strong amplification product in the non-source species. From these 44 putative comparative anchor tags, 19 (15 from Quercus and 4 from Castanea) were integrated in two previously established genetic linkage maps for the two genera. SSR loci were sequenced to confirm the orthology of the markers. The combined information from both genetic mapping and sequence analysis were used to determine the homeology between seven linkage groups, aligned on the basis of pairs or triplets of common markers, while two additional groups were matched using a single microsatellite marker. Orthologous loci identified between Q. robur and C. sativa will be useful as anchor loci for comparative mapping studies within the Fagaceae family.

Comparison of ISSR and RAPD markers to characterize three Chilean Nothofagus species.

The present study is the first report of fingerprinting on three Chilean Nothofagus species using ISSR and RAPD markers; 61 Nothofagus nervosa, 32 Nothofagus obliqua and 32 Nothafagus dombeyi individual trees, sampled from collection and natural sites, were analyzed. Among 45 primers tested, the 6 ISSR and 6 RAPD primers selected for the analysis generated a total of 63 ISSR and 42 RAPD fragments. A high proportion of polymorphic bands, ranging from 97% and 80%, was found using both markers. A similar number of private and marker bands was generated by both markers in all the species examined and one discriminant ISSR fragment was obtained for N. dombeyi. Jaccard and Dice similarity indices were used to evaluate pairwise genetic divergence; cluster analysis of the similarity matrices was performed to estimate the intra- and inter-specific genetic diversity, and PCA analysis was employed to evaluate the resolving power of the markers to differentiate between the species. These analyses, carried out for both markers, allowed us to identify three main groups corresponding to the three Nothofagus species. The results of the present study can be seen as a starting point for future researches on the population and evolutionary genetics of these species.