Marianna Hagidimitriou

Genetic relationships among species and cultivars of Pistacia using RAPDs and AFLPs

The genus Pistacia (Anacardiaceae) includes 11 species divided into four sections, according to leaf characters and nut morphology. Recently two monophyletic groups have been proposed by using cpDNA,Lentiscus and Terebinthus,containing evergreen and deciduous species, respectively. In the present work molecular markers, derived from two different methods, RAPD and AFLP, are used to study the relationships of native and introducedPistacia species present in Greece. According to the cophenetic correlation coefficients best results for both methods were obtained by using the Jaccard algorithm and the UPGMA clustering method. However, phenograms were constructed using the NJ method (rcs= 0.987 for RAPDs and rcs= 0.982 for AFLP), since it is less sensitive against varying mutation rates. Correlation among the genetic similarity (GS) matrices for the two methods was high(r = 0.941). The AFLP and RAPD phenograms were comparable with minor clustering differences. According to our results, two main branches are obtained, one containing the evergreen species P. lentiscusand the resin producing P. lentiscuscv. Chia (cultivated only in the island of Chios), and the other branch containing the deciduous species P. terebinthus,P. palaestina and P. vera, P. chinensis was clustered either with the evergreen species (RAPD data) or with the deciduous species (AFLP data). P. palaestina is clustered to P. terebinthus and can be considered as a subspecies of P. terebinthus, since its GS values are close or smaller than GS values of entries within species (P. vera). The four female cultivars were found to have a narrow genetic basis, probably related to cultivar ‘Nazareth‘ with Syrian origin.

Genetic diversity and relationships among Pistacia species and cultivars

Iran is one of the two major centres of Pistacia diversity and the main producer of pistachios in the world. About 282 Iranian pistachio genotypes (Pistacia spp.), together with 22 foreign cultivars (P. vera), were genotyped using 10 simple sequence repeat (SSR) markers to analyse the genetic diversity and relationships among Pistacia species and cultivars. The results revealed that the genetic diversity within P. atlantica subsp. kurdica was considerably lower than in P. vera or P. khinjuk. Principal coordinate analysis revealed a clear separation between the different Pistacia spices, as well as between the Iranian and foreign cultivars. AMOVA analysis showed that the variation between the species, between different populations, and within populations accounted for 41, 9, and 50% of the total variation, respectively. The results demonstrated that the study of genetic diversity and relationships among Pistacia species and cultivars using SSR markers provides important information for the collection and conservation of pistachio germplasm. In addition, the Iranian cultivars had a broader genetic background than that of the foreign cultivars. Thus, they are very important for genetic conservation and the planning of future breeding programmes. We also determined the different levels of genetic diversity that exist between and within the species and populations and showed that gene flow occurs between the Iranian cultivars and wild-type P. vera populations. The study provides practical information that policy-makers and scientists can apply to the conservation and sustainable use of all the species studied.

Genomic and chromosomal organization of Ty1-copia-like sequences in Olea europaea and evolutionary relationships of Olea retroelements

Abstract.The Ty1-copia-like retrotransposon is one of the commonest class of transposable elements in the plant kingdom, often comprising several percent of the total DNA content. We aimed to study the evolutionary relationships of Olea retroelements, using part of the reverse transcriptase domain, as well as the genomic and chromosomal organization of these sequences in Olea europaea chromosomes and their transcription activity and copy number. Fourteen clones, that were isolated from four different species, were sequenced and a phylogenetic tree was constructed based on their predicted amino acids. Five clones derived from O. europaea were clustered together with a 87% nucleotide sequence homology and two Olea oleaster clones showed 98% sequence homology. The rest of the clones showed heterogeneity among them, leading to a common ancestral transposon that existed before the genus arose. The Ty1-copia-like sequences have a dispersed genomic organization, physically distributed on all chromosomes, showing minor clustering in some cases and low copy numbers in the smallest chromosome pair. The total copy number in the O. europaea genome was estimated by dot blotting to be 40,000 in a haploid nucleus, but a number of these are non-functional since the sequenced clones contained stop codons and frame-shifts. Some Ty1-copia-like copies, present in O. europaea, were found to be methylated, while no differences in methylation were observed between DNA isolated from young leaves and callus-suspension cultures.

Analysis of the molecular variation between and within cultivated and wild Pistacia species using AFLPs

Knowledge of pistachio genetic diversity is necessary for the formulation of appropriate management strategies for the conservation of these species. We analysed amplified fragment length polymorphisms in a total of 216 pistachio accessions, which included seven populations from three wild species (Pistacia vera, Pistacia khinjuk and Pistacia atlantica subsp. kurdica) and most of the important cultivars from Iran, together with some foreign cultivars. High levels of genetic diversity were detected within the Iranian cultivars, and they showed a clear separation from foreign cultivars, as revealed by unweighted pair group method with arithmetic averaging and supported by analysis of molecular variance. The lowest amount of polymorphism was observed in P. atlantica subsp. kurdica, which showed the lowest number of total bands as compared to the other species. This revealed strong genetic erosion of P. atlantica subsp. kurdica, which reflected a severe decline in habitat and over-exploitation. Based on these findings, strategies are proposed for the genetic conservation and management of pistachio species and cultivars.

Monumental olive trees of Cyprus contributed to the establishment of the contemporary olive germplasm

Even though Cyprus was an important crossing point for the westward spread of olive, and one of the primary regions of domestication, its genetic recourses remain uncharted at a great extent. Throughout the centuries, a number of ancient olive trees remain in the same orchards, contributing to Cypriot oleiculture and society. In an attempt to explore this monumental genetic pool, a survey was conducted to identify centennial olive trees in rural provinces of Cyprus. Microsatellites were employed in order to study their genetic composition (including rootstocks when feasible) and to establish possible associations among genotypes. High numbers of specific alleles, suggestive of the distinctiveness of this germplasm, were detected, and both grafting and rootstock propagation was verified. Moreover, it was determined by Bayesian structural and network reticulate analysis that centennial olives can be divided in two discrete genetic clusters having intermediate admixed accessions. Furthermore, it was determined that all contemporary Cypriot cultivars, that were included in the present study, were highly affiliated exclusively to one genetic group, a strong evidence of selection among elite clones. The information acquired from the current study reveals the genetic rareness of this material and its contribution to the current olive germplasm.