Contemporary pollen flow, characterization of the maternal ecological neighbourhood and mating patterns in wild cherry (Prunus avium L.).

Conversion of lowland woodland to agricultural land and resulting fragmentation in Britain has been ongoing since Neolithic times. To counteract this decline, plantations of native species, often based on non-British planting stock, have been established. This may ultimately be detrimental to the integrity of the native gene pool. We explore the genetic and ecological factors influencing the success of components of the local pollen pool, including the effect of a non-native planting on an ancient woodland population of wild cherry. Wild cherry exhibits gametophytic self-incompatibility (GSI) and vegetative reproduction, both of which may be determinants of paternal success. The majority (61%) of the successful pollen originated from within the study site with a maximum pollen transfer distance of 694 m. There was a distinct departure from random mating, with over half the successful pollen originating from trees which occur within 100 m of the mother tree. Self-incompatibility, clonality, tree size and proximity to the mother tree were all found to influence paternal success. Kinship of pollen gametes within a maternal progeny was highest when a mother tree was surrounded by a large number of ramets of a single, compatible clone consisting of large, adult trees. Although the contribution from the non-native plantation is currently low, it is likely that this will increasingly contribute to the progeny of the adjacent ancient population as it matures. The results clearly show that in self-incompatible species, such as P. avium, close neighbours may be pollinated by very different components of the local pollen pool.

Characterization of Hawaiian isolates of Cymbidium mosaic virus (CymMV) co-infecting Dendrobium orchid.

We report here the isolation and characterization of three distinct isolates of Cymbidium mosaic virus (CymMV) co-infecting Dendrobium orchid in Hawaii. Isolates 1 and 2 were phylogenetically distinct from previously reported CymMV isolates. However, isolate 3 was highly similar to previously reported CymMV sequences and could be localised to CymMV subgroup A. Isolate 2 localised to CymMV subgroup B. Thus, we report here the first full-length CymMV subgroup B isolate. Isolate 1 represents a recombination event between isolates 2 and 3. Infectivity assays revealed that all three isolates are functional and individually infectious in both Dendrobium and indicator species.

Distribution and fine-scale spatial-genetic structure in British wild cherry (Prunus avium L.).

Insights into the within-population spatial-genetic structure (SGS) of forest tree species, where little is known regarding seed and pollen dispersal patterns, enhance understanding of their ecology and provide information of value in conservation and breeding. This study utilised 13 polymorphic simple sequence repeat loci to investigate the impact of asexual recruitment, management regime and tree size on the development of SGS in wild cherry (Prunus avium L). Only 246 genotypes were identified in the 551 trees sampled, reflecting significant levels of clonal reproduction in both managed and unmanaged populations. Naturally regenerated wild cherry was spatially aggregated under both management regimes. However, in the managed population, sexually derived trees accounted for a greater proportion of the smaller size classes, whereas vegetatively produced trees dominated the smaller size classes in the unmanaged population. High overall SGS values (Sp 0.030-Sp 0.045) were observed when considering only sexually derived genets and kinship coefficients were significant up to the 120 m distance class for both populations. The inclusion of clonal ramets in the analysis significantly increased the overall SGS (Sp 0.089-Sp 0.119) as well as kinship coefficients in the 40-80 m distance classes, illustrating the dramatic impact of vegetative propagation on SGS in this species. Increased spatial aggregation and regeneration appeared to be concomitant with increased SGS in the 40 m distance class in the unmanaged population. Neighbourhood size estimates were relatively small for both populations and kinship coefficients were found to decline with distance under both management regimes, suggesting that common mechanisms may restrict gene dispersal in wild cherry.

Isolation of S-locus F-box alleles in Prunus avium and their application in a novel method to determine self-incompatibility genotype.

This study characterises a series of 12 S-locus haplotype-specific F-box protein genes (SFB) in cherry (Prunus avium) that are likely candidates for the pollen component of gametophytic self-incompatibility in this species. Primers were designed to amplify 12 SFB alleles,including the introns present in the 50 untranslated region;sequences representing the S-alleles S1, S2, S3, S4, S40, S5,S6, S7, S10, S12, S13 and S16 were cloned and characterized. [The nucleotide sequences reported in this paper have been submitted to the EMBL/GenBank database under the following accession numbers: PaSFB1(AY805048), PaSFB2 (AY805049), PaSFB3 (AY805057),PaSFB4 (AY649872), PaSFB40 (AY649873), PaSFB5(AY805050), PaSFB6 (AY805051), PaSFB7 (AY805052),PaSFB10 (AY805053), PaSFB12 (AY805054), PaSFB13(AY805055), PaSFB16 (AY805056).] Though the coding regions of six of these alleles have been reported previously,the intron sequence has previously been reported only for S6. Analysis of the introns revealed sequence and length polymorphisms. A novel, PCR-based method to genotype cultivars and wild accessions was developed which combines fluorescently labelled primers amplifying the intron of SFB with similar primers for the first intron of S-RNase alleles. Intron length polymorphisms were then ascertained using a semi-automated sequencer. The convenience and reliability of this method for the determination of the self-incompatibility (SI) genotype was demonstrated both in sweet cherry cultivars representing alleles S1 to S16 and in individuals from a wild population encompassing S-alleles S17 to S22. This method will greatly expedite SI characterisation in sweet cherry and also facilitate large-scale studies of self-incompatibility in wild cherry and other Prunus populations.