We report the sequence of 41 primer pairs of microsatellites from a CT-enriched genomic library of the peach cultivar 'Merrill O'Henry'. Ten microsatellite-containing clones had sequences similar to plant coding sequences in databases and could be used as markers for known functions. For microsatellites segregating at least in one of the two Prunus F(2) progenies analyzed, it was possible to demonstrate Mendelian inheritance. Microsatellite polymorphism was evaluated in 27 peach and 21 sweet cherry cultivars. All primer pairs gave PCR-amplification products on peach and 33 on cherry (80.5%). Six PCR-amplifications revealed several loci (14.6%) in peach and eight (19.5%) in sweet cherry. Among the 33 single-locus microsatellites amplified in peach and sweet cherry, 13 revealed polymorphism both in peach and cherry, 19 were polymorphic only on peach and one was polymorphic only on cherry. The number of alleles per locus ranged from 1 to 9 for peach and from 1 to 6 on sweet cherry with an average of 4.2 and 2.8 in peach and sweet cherry, respectively. Cross-species amplification was tested within the Prunus species: Prunus avium L. (sweet cherry and mazzard), Prunus cerasus L. (sour cherry), Prunus domestica L. (European plum), Prunus amygdalus Batsch. (almond), Prunus armeniaca L. (apricot), Prunus cerasifera Ehrh. (Myrobalan plum). Plants from other genera of the Rosaceae were also tested: Malus (apple) and Fragaria (strawberry), as well as species not belonging to the Rosaceae: Castanea (chestnut tree), Juglans (walnut tree) and Vitis (grapevine). Six microsatellites gave amplification on all the tested species. Among them, one had an amplified region homologous to sequences encoding a MADS-box protein in Malus x domestica. Twelve microsatellites (29.3%) were amplified in all the Rosaceae species tested and 31 (75.6%) were amplified in all the six Prunus species tested. Thirty three (80.5%), 18 (43.9%) and 13 (31.7%) gave amplification on chestnut tree, grapevine and walnut tree, respectively.

A gene diversity survey was conducted on a range-wide sample of 81 populations of Quercus petraea. Allele frequencies were calculated at 13 enzyme-coding loci, of which 11 were polymorphic. There was a clear discrepancy in the levels of diversity at loci controlling enzymes of primary metabolism compared with those involved in secondary metabolism, the latter being more variable than the former. Quercus petraea is a highly variable species as are other longlived widespread forest species: at the species level, the mean number of alleles per population was 4.77 and the expected heterozygosity 0.265. Populations from the central part of the natural range exhibited fewer alleles but higher heterozygosities than populations from the margins of the distribution. Significant correlations were observed between allele frequencies and longitude for most loci, resulting in a dma! variation of allele frequencies across a continental gradient. The patterns of geographical variation in allele frequencies and levels of diversity were interpreted as a consequence of postglacial migration pathways.

Host specialization plays a key role in the extreme diversification of phytophagous insects. Whereas proximate mechanisms of specialization have been studied extensively, their consequences for species divergence remain unclear. Preference for, and performance on hosts are thought to be a major source of divergence in phytophagous insects. We assessed these major components of specialization in two moth species, the European corn borer (ECB) and the Adzuki bean borer (ABB), by testing their oviposition behaviour in different conditions (choice or no-choice set-ups) and their performances, by reciprocal transplant at the larval stage on the usual host and an alternative host plant. We demonstrated that both ABB and ECB have a strong preference for their host plants for oviposition, but that relative larval performances on the usual host and an alternative host differed according to the experiment and the trait considered (weight or survival). Finally, we show for the first time that the preference for maize in ECB conceals a strong avoidance of mugwort. The differences in performance, attraction and avoidance between ECB and ABB are discussed in the light of the underlying mechanisms and divergence process.

Prunus avium L. (diploid, AA, 2n ¼ 2x ¼ 16), Prunus cerasus L. (allotetraploïd, AAFF, 2n ¼ 4x ¼ 32) species, and their hybrid Prunus  gondouinii Rehd., constitute the most widely cultivated cherry tree species. P. cerasus is supposed to be an hybrid species produced by the union of unreduced P. avium gametes and normal P. fruticosa gametes. A continuum of morphological traits between these three species makes their assignation difficult. The aim of this paper is to study the genetic relationships between tetraploid and diploid cherry species. In all, 114 genotypes belonging to these species were analyzed using 75 AFLP markers. The coordinates of these genotypes on the first axis of a correspondence analysis allowed us to clearly distinguish each species, to identify misclassifications and to assign unknown genotypes to one species. We showed that there are specific alleles in P. cerasus, which are not present in the A genome of P. avium and which probably come from the F genome of P. cerasus. The frequencies of each marker in the A and the F genomes were estimated in order to identify A and F specific markers. We discuss the utility of these specific markers for finding the origin of the A and F genomes in the allopolyploid species.

Geostatistics were used for describing and modelling spatial patterns of gene frequencies at eight allozyme loci in 93 populations of sessile oak well distributed over the natural range of the species. Spatial patterns were summarized by the variogram, a measure of gene frequency variance as a function of distance. They were of three kinds: stationary patterns, clines and random distributions of allele frequencies. The main directions of variation of gene frequencies over Europe were estimated using directional geostatistics. They were shown to reflect postglacial migration routes as well as a genetic divergence among populations from different glacial refugia. A method of spatial interpolation, called kriging, was used to draw synthetic maps for allele frequencies and for multilocus patterns of variation using two canonical variables. It appears from this study that geostatistics are useful tools for the description of complex patterns of genetic variation, and therefore also for the management of natural genetic resources in forest trees.