O. Lain

A consensus list of microsatellite markers for olive genotyping

Cultivar identification is a primary concern for olive growers, breeders, and scientists. This study was aimed at examining the SSR markers retrieved from the literature and currently used in olive study, in order to select those most effective in characterizing the olive accessions and to make possible the comparison of data obtained by different laboratories. Olive microsatellite profiles were assessed by four independent laboratories, which analyzed 37 pre-selected SSR loci on a set of 21 cultivars. These SSR markers were initially tested for their reproducibility, power of discrimination and number of amplified loci/alleles. Independent segregation was tested for each pair of SSRs in a controlled cross and the allelic error rate was quantified. Some of them were finally selected as the most informative and reliable. Most of the alleles were sequenced and their sizes were determined. Profiles of the reference cultivars and a list of alleles with their sizes obtained by sequencing are reported. Several genetic parameters have been analysed on a larger set of cultivars allowing for a deeper characterization of the selected loci. Results of this study provide a list of recommended markers and protocols for olive genotyping as well as the allelic profile of a set of reference cultivars that would be useful for the establishment of a universal database of olive accessions.

A kiwifruit (Actinidia spp.) linkage map based on microsatellites and integrated with AFLP markers

Abstract A genetic map of kiwifruit (Actinidia spp.) was constructed using microsatellite and AFLP markers and the pseudo-testcross mapping strategy. (AC)n and (AG)n microsatellite repeats were first isolated from Actinidia chinensis (2n = 2x = 58) enriched genomic libraries and tested for segregation in the interspecific cross between the diploid distantly related species A. chinensis and A. callosa. Some 105 microsatellite loci of the 251 initially tested segregated in the progeny in a 1:1 ratio as in a classical backcross, or in a ratio which could mimic the backcross, and were mapped using 94 individuals. AFLP markers were then produced using MseI and EcoRI restriction enzymes and 15 primer combinations. Nearly 10% of loci showed a distorted segregation at α = 0.05, and only 4% at α = 0.01, irrespectively to the marker class. Two linkage maps were produced, one for each parent. The female map had 203 loci, of which 160 (71 SSR and 89 AFLP) constituted the framework map at a LOD score ≥ 2.0. The map was 1,758.5 cM(K) long, covering 46% of the estimated genome length. The male map had only 143 loci, of which 116 (28 SSR, 87 AFLP and the sex determinant) constituted the framework map. The map length was only 1,104.1 cM(K), covering 34% of the estimate genome length. Only 35 SSR loci were mapped in the male parent because 18% of SSR loci that were characterised did not amplify in A. callosa, and 48% were homozygous. The choice of parents in the pseudo-testcross is critically discussed. The sex determinant was mapped in A. callosa.

Linkage map saturation, construction, and comparison in four populations of Prunus

Summary One of the objectives of the ISAFRUIT Project was to perform genetic analyses in four populations of Prunus, two of peach (P. persica) and two of apricot (P. armeniaca), in order to identify major genes and quantitative trait loci (QTLs) for characters related to fruit quality. This required the construction of saturated marker maps in each of these populations. Marker maps were available for an intra-specific peach × peach F2, a BC2 peach × P. davidiana (using peach as the recurrent parent), and an apricot × apricot F1. We have further saturated these maps mainly with SSR (simple sequence repeat) markers. A new map, constructed uniquely from SSRs was prepared for a fourth apricot × apricot F1 population. Using anchor markers, we compared these four maps with the reference Prunus map, constructed using an almond × peach F2 population. As previously observed, conservation of synteny and co-linearity were the general rule, providing additional evidence of the high level of similarity between all Prunus genomes. Comparisons of genetic distances between the maps suggested that those involving similar genomes had higher levels of recombination than those with more distant genomes, particularly the inter-specific crosses.

A natural sex mutant in kiwifruit (Actinidia deliciosa)

Abstract A kiwifruit (Actinidia deliciosa) natural sex mutant is described. The bud mutation occurred in a mature male vine and caused a gender change from male to female. The mutant (ser, sex reversal) carries apparently perfect flowers, with a well developed ovary and styles, but produces pollen that does not germinate and does not fertilise female genotypes. The ser mutant sets fruits when pollinated with pollen from the original or any other male, but not when selfed. The origin of the mutant as a sport mutation was confirmed by the identical genetic profile of both mutated and original canopy sectors at 12 microsatellite loci. Both the original and mutant parts of the vine were phenotypically stable on propagation by grafting. The paper discusses the likely genetic origin of the mutant and its usefulness for studying the genes that control dioecy in Actinidia.

Observation of eight ancient olive trees (Olea europaea L.) growing in the Garden of Gethsemane.

For thousands of years, olive trees (Olea europaea L.) have been a significant presence and a symbol in the Garden of Gethsemane, a place located at the foot of the Mount of Olives, Jerusalem, remembered for the agony of Jesus Christ before his arrest. This investigation comprises the first morphological and genetic characterization of eight olive trees in the Garden of Gethsemane. Pomological traits, morphometric, and ultrastructural observations as well as SSR (Simple Sequence Repeat) analysis were performed to identify the olive trees. Statistical analyses were conducted to evaluate their morphological variability. The study revealed a low morphological variability and minimal dissimilarity among the olive trees. According to molecular analysis, these trees showed the same allelic profile at all microsatellite loci analyzed. Combining the results of the different analyses carried out in the frame of the present work, we could conclude that the eight olive trees of the Gethsemane Garden have been propagated from a single genotype.