Search

SummaryStandard models of plant speciation assume strictly dichotomous genealogies in which a species, the ancestor, is replaced by two offspring species. The reality in wind-pollinated trees with long evolutionary histories is more complex: species evolve from other species through isolation when genetic drift exceeds gene flow; lineage mixing can give rise to new species (hybrid taxa such as nothospecies and allopolyploids). The multi-copy, potentially multi-locus 5S rDNA is one of few gene regions conserving signal from dichotomous and reticulate evolutionary processes down to the level of intra-genomic recombination. Therefore, it can provide unique insights into the dynamic speciation processes of lineages that diversified tens of millions of years ago. Here, we provide the first high-throughput sequencing (HTS) of the 5S intergenic spacers (5S-IGS) for a lineage of wind-pollinated subtropical to temperate trees, theFagus crenata – F. sylvaticas.l. lineage, and its distant relativeF. japonica.The observed 4,963 unique 5S-IGS variants reflect a complex history of hybrid origins, lineage sorting, mixing via secondary gene flow, and intra-genomic competition between two or more paralogous-homoeologous 5S rDNA lineages. We show that modern species are genetic mosaics and represent a striking case of ongoing reticulate evolution during the past 55 million years.Significance statementThe evolution of extra-tropical wind-pollinated tree genera involves dynamic speciation processes. High-throughput sequencing of the multi-copy, potentially multi-locus 5S rDNA reveals a complex history of hybrid origins, lineage sorting and mixing, and intra-genomic competition between paralogous-homeologous loci in the core group of Eurasian beech trees (genusFagus) and their distant relative,F. japonica. The modern species are genetic mosaics and represent a striking case of at least 55 million years of ongoing reticulate evolution.

Ferula assa-foetida and F. gummosa, Apiaceae, are important endemic and endangered medicinal plants. Survival of the species is threatened by climate change, overexploiting (as source of oleo-gum resin and forage) and lack of organized cultivation. Cultivation of these valuable medicinal plants is restricted by insufficient domestication knowledge. Germination characteristics of different popula-tions of Ferula taxa were studied with the aim of describing and comparing their responses to continu-ous cold stratification condition. Germination cues for the species were complex, with dormancy mechanisms present to restrict germination until cold stratification are fulfilled. Results indicated that a period of 4 weeks of stratification is sufficient for germination of F. assa-foetida, but optimal germi-nation of F. gummosa require stratification for periods of 8 weeks. Both species were able to germi-nate at very low temperatures (4°C). Within-taxon differences in dormancy breaking and seedling emergence may interpret as local adaptations. The continued regeneration and propagation of the species in the wild will depend on the temperature and moisture status of the soil during winter and the maintenance of conditions suitable for stratification for an appropriate length of time.

The present study was carried out to evaluate aerial yield, agronomic traits, essential oil production, and their relationships in 21 populations of Ziziphora tenuior in Karaj, Iran over two years (2016–2017). The experimental layout was a randomized complete block design with three replications. Data were collected for GDD (Growth Degree Days), plant height, canopy area, stem number, flower number, aerial fresh yield, aerial dry matter (DM) yield, seed yield, essential oil percentage and oil production. The essential oil compositions were detected in accession 2929 (Tassoj) using GC/MS. Result of combined analysis of variance across two years showed significant differences between years, populations and population x year interaction for all traits (P < 0.01). In comparisons among populations, the population of Avaj and Ijroud with average values of 13.5 and 14.33 g/p had higher aerial dry yield and other agronomic traits followed by Meshkin2 and 3. For seed yield, Ormieh with average values of 3.11 g/p had higher production. For oil content, the populations of Tassoj, Salmas and Sharkord with average values of 1.25 to 1.56% had higher oil content and essential oil production. Result of correlation analysis showed that DM yield was positively correlated with GDD, plant height, canopy area, stem number, flower number. Oil content was negatively correlated with aerial DM yield. The results of PCA analysis showed that the first four components accounted for 50, 20, 12 and 10% of the total variation, respectively. Plant height, canopy area, stem number, flower number and aerial yield in the PCA1, essential oil content and oil production in the PCA2, seed yield in the PCA3 and GDD in PCA4 components were identified as important traits. Using Ward cluster method, the 21 populations were grouped into 3 clusters. In total, 23 compounds were identified in the essential oil from the aerial parts Z. tenuior. The major components in the essential oil were pulegone ranged (47.54 to 65.26%) followed by neo-iso-dihydro carveol, carvacrol, piperitenone, limonene, 1.8-cineole, p-mentha-3,8-dien, alpha-terpinene and terpinen-u-ol. It was concluded that there were wide range of variations for agronomic trait and essential oil in domestic germplasm of Z. tenuior to improved breeding new varieties in Iran.

Background Buxus hyrcana (boxwood) is an endangered species in the Hyrcanian forests in the north of Iran. This tree is threatened by habitat loss but faces additional threats from the introduced disease the boxwood blight (caused by the fungus Calonectria pseudonaviculata syn. Cylindrocladium pseudonaviculatum, Cy. buxicola) and the potential effects of climate change. As wide range of genetic polymorphism is necessary to ensure successful adaptation to rapid climatic changes. Methods Genetic diversity and differentiation between 15 healthy and 15 infected trees of each of two populations were studied using RAPD and ISSR molecular markers. Results High-band polymorphism was found in pooled samples of B. hyrcana using both ISSR (58%) and RAPD (73%) markers. The ISSR data and the combined data set classified the trees into two groups. However, data from RAPD clustered the trees into three groups. These results indicate different degrees of genetic variation in the sequences of the tested B. hyrcana genomes targeted by the two marker types used. Genetic variation was found to be relatively high, with most of the diversity occurring within populations. Analyses of healthy versus infected pooled samples based on both marker types indicated that genetic diversity parameters were mostly higher in healthy trees. Conclusions Boxwood blight has had a major effect on B. hyrcana, killing individual stems quickly especially in dense populations and reducing population size (as observed in all populations). Considerable within-population diversity, and higher genetic variability in healthy trees than infected ones, suggested conservation efforts should focus on survivor trees in each population and consider the establishment of tree reservations. Propagation of plants from seeds is preferred, since it would include the widest range of genetic variation.

Genetic variation is an important attribute of forest tree populations enabling them to adapt to spatial and temporal variations in environmental conditions. In particular, Scots pine (Pinus sylvestris L.) has an exceptionally broad area of dispersal covering different climates and soil conditions, but the genetic variability in extreme conditions has not been studied. We hypothesized that the genetic variability of P. sylvestris is enhanced at its soil fertility limit in bogs where stunted trees form a sparse canopy with reduced light competition, but in highly turbulent conditions generating ideal conditions for distant pollen dispersal. A total of 180 individuals were studied from three bog populations using five nuclear (nSSR) and five chloroplastic (cpSSR) polymorphic microsatellite loci (simple sequence repeats, SSR). According to both marker systems, high and similar level of genetic diversity (ca. 99 % within the populations and 1 % among the populations) was observed for nuclear (F ST = 0.007 and R ST = 0.022) and chloroplast (F ST = 0.015 and R ST = 0.023) genomes. Despite the low genetic differentiation among the populations, there was evidence of geographic genetic differentiation in the chloroplast genomes, suggesting that isolation by distance might be a possible mechanism shaping the present distribution of genetic variability. In addition, significant but low spatial genetic structure along habitat wetness gradient was found in nuclear genomes in one site. Significant cyto-nuclear linkage disequilibrium was shown between one of the cpSSR loci to all nSSR loci. The results demonstrate a huge within-population genetic variability in these sites and underscore the importance of pollen gene flow in homogenizing populations on these geographic scales.

The effects of water potential on germination were studied in 18 wild populations of three yarrow species (Achillea tenuifolia, A. vermicularis and A. filipendulina) from different bioclimatic zones in Iran. Water potential between 0 and -0.6 MPa were obtained using polyethylene glycol 6000 (PEG-6000) solutions. The study of water stress on germination showed that, regardless of the species and the populations, the lowering of the water potential reduced the capacity for germination and early seeding growth. These results indicated a strong genetic potential for drought tolerance during germination within each species. These differences in germination ability of wild populations of each species might be attributed to intraspecific variations resulting from the effects of natural selection and genetic pool background.

Oriental beech (Fagus orientalis Lipsky) is a widespread monoecious and wind-pollinated tree species. It is one of the major components of the Hyrcanian forests of Iran and it is of both ecological and economical importance. Twelve beech stands were surveyed at 9 chloroplast (cp) and 6 nuclear (n) polymorphic microsatellite loci (simple sequence repeats, SSR) to provide information on distribution of genetic diversity within and among populations and on gene conservation and silvicultural management of this species. High levels of genetic differentiation were detected for the chloroplast genome (FST = 0.80 and RST = 0.95), in sharp contrast to the nuclear genome (FST = 0.06, RST = 0.05). The analysis of molecular variance (AMOVA) showed that 48% of the total cpSSR variation was attributable to differences among regions and 30% to differences among populations within regions, suggesting multiple origins of beech populations in Hyrcanian forests. Nuclear SSRs confirmed the presence of significant differentiation among populations and among geographic regions, even if, as expected, this was less pronounced than that found with cpSSRs (based on AMOVA, differences among regions and among populations within regions each contribute 5% to total nSSR variance). A highly significant correlation between genetic (nSSRs) and geographic distances (R2 = 0.522) was estimated, thus showing an isolation by distance effect. The application of spatial analysis of molecular variance (SAMOVA) using both marker data allowed identification of genetically homogeneous groups of populations. Possible applications of these results for the certification of provenances and/or seed lots and for designing conservation programs are presented and discussed.

The volatile constituents of the foliage and berries (female cones) of Juniperus excelsa trees from Iran were analyzed by GC and GC–MS. Twenty six constituents were identified and quantitated. Considerable seasonal variation was found in the berry oils, in contrast with the foliage oils. The oil yields in berries increased by 162% from spring to autumn as the berries matured. The amount of α-pinene decreased in the foliage oil during the summer; however it increased in the berry oil. Seasonal variation of other constituents showed various patterns. Seasonal variation in the berry oil was much greater than in the foliage oil. A comparison of oils from fresh vs. dried foliage and berries revealed changes in the amounts of several constituents. α-Pinene decreased after drying, whereas the amounts of several other constituents in the foliage and berry oils increased. This study shows that for the industrial utilization of J. excelsa berry oils, the harvesting period is a critical factor. However, either fresh or dried foliage can be utilized for leaf oil production.

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.

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. © Springer Science+Business Media B.V. 2009.

CpDNA variation in Iranian beech, Fagus orientalis Lipsky (Fagaceae) was studied in 14 populations distributed throughout the species range in the Hyrcanain zone. Two cpDNA intergenic regions were analyzed: (i) one in the DT region between trnD (tRNA-Asp) and trnT (tRNA-Thr) genes, and (ii) one in the OA region between the orf184 and petA genes. The restriction fragments of the region DT did not show polymorphism among individuals within any population analyzed. However, among individuals within analyzed populations of Asalem region and Neka-1400 population, polymorphism in the restriction fragments of the OA region were found. A total of 3 different chloroplast (cp) haplotypes were scored. The distribution of the cpDNA haplotypes revealed a geographical structure of the genetic differentiation with Gst = %68.7 and Nst = %70.3. The distribution pattern of F. orientalis cpDNA haplotypes may reflect environmental differences and migration history of beech during historical distribution in Tertiary from Asalem (most polymorphic region) to East of Hyrcanian forests.

The aim of this study was to compare some stability analyses methods as additive main effect and the multiplicative interaction analysis (AMMI), Eberhart-Russel regression, cultivar superiority (Pi), ecovalence (Wi), and stability variance analysis in classification of dry matter (DM) yield in 38 sainfoin (Onobrychis sativa L.) genotypes across five environments of Iran over 2 years (2010 and 2011). Results of combined analysis of variance showed significant differences effects of genotypes, environments, and genotype × environment interaction. In comparison among various stability methods results showed that five of the 38 tested genotypes as 3 (Sarab), 8 (Khomin), 24 (Khonsar), 37 (Divandara) and 38 (Songor) with average values of 7.18 to 7.85 t had high and stable DM yield and wide-general adaptability. Other tested cultivars had unstable yield and narrow (specific) adaptability.