High genetic diversity and clonal growth in relict populations of Olea europaea subsp. laperrinei (Oleaceae) from Hoggar, Algeria.

The Laperrine's olive (Olea europaea subsp. laperrinei) is an endemic tree from Saharan massifs. Its populations have substantially regressed since the Pleistocene and are presently distributed in a fragmented habitat. Long-term persistence of this taxon is uncertain and programmes of preservation have to be urgently implemented. To define a conservation strategy, the genetic diversity and breeding system of this tree have to be investigated. One hundred and eleven ramets were prospected in the laperrinei populations from the Tamanrasset region, southern Algeria. Genetic polymorphism was revealed at nuclear and chloroplast DNA (cpDNA) microsatellite loci allowing a comparative assessment of the genetic diversity of laperrinei and Mediterranean populations based on bi-parental and maternal markers. Additionally, nuclear microsatellite markers enabled the genotypes to be identified unambiguously. Based on nuclear microsatellite data, the total diversity was high (Ht=0.61) in laperrinei populations and similar to that observed in western Mediterranean populations. A substantial cpDNA diversity (Ht=0.19) was also observed. Genetically identical ramets originated from the same stump (which can cover >80 m2) were identified in each population. Sixteen per cent of genets exhibited more than one ramet. In addition, several cases of somatic mutations were unambiguously revealed in distinct ramets stemming from the same stump. These data show that highly isolated and small laperrinei populations are able to maintain a high genetic diversity. This supports the existence of relict trees persisting for a very long time (probably since the last humid transition, 3000 years ago). It is proposed that the very long persistence associated with an asexual multiplication of highly adapted trees could be a strategy of survival in extreme conditions avoiding a mutational meltdown due to reproduction in reduced populations

On the origin of the invasive olives (Olea europaea L., Oleaceae).

The olive tree (Olea europaea) has successfully invaded several regions in Australia and Pacific islands. Two olive subspecies (subspp. europaea and cuspidata) were first introduced in these areas during the nineteenth century. In the present study, we determine the origin of invasive olives and investigate the importance of historical effects on the genetic diversity of populations. Four invasive populations from Australia and Hawaii were characterized using eight nuclear DNA microsatellites, plastid DNA markers as well as ITS-1 sequences. Based on these data, their genetic similarity with native populations was investigated, and it was determined that East Australian and Hawaiian populations (subsp. cuspidata) have originated from southern Africa while South Australian populations (subsp. europaea) have mostly derived from western or central Mediterranean cultivars. Invasive populations of subsp. cuspidata showed significant loss of genetic diversity in comparison to a putative source population, and a recent bottleneck was evidenced in Hawaii. Conversely, invasive populations of subsp. europaea did not display significant loss of genetic diversity in comparison to a native Mediterranean population. Different histories of invasion were inferred for these two taxa with multiple cultivars introduced restoring gene diversity for europaea and a single successful founder event and sequential introductions to East Australia and then Hawaii for cuspidata. Furthermore, one hybrid (cuspidata x europaea) was identified in East Australia. The importance of hybridizations in the future evolution of the olive invasiveness remains to be investigated

Microsatellite markers for identification of a group of italian olive accessions

Cultivar characterization for fruit trees certification requires fast, efficient and reliable techniques. Microsatellite markers (SSR) were used in the molecular characterization of 23 genotypes of Olea europaea subsp europaea. The DNA from the olive cultivars was analyzed using nine pre-selected SSR primers (GAPU59, GAPU71A, GAPU71B, GAPU103A, UDO99-01, UDO99-12, UDO99-28 and UDO99-39) and revealed 29 alleles, which allowed each genotype to be identified. In the dendrogram, the nine primers allowed the 23 olive genotypes to be grouped into subgroups corresponding to the same cultivar denominations. SSR markers proved to be efficient and reliable for the molecular characterization of Italian olive cultivars.A caracterização de cultivares na produção de mudas certificadas exige técnicas rápidas, eficientes e confiáveis. Marcadores microssatélites (SSR) foram utilizados objetivando a caracterização molecular de 23 genótipos de Olea europaea subsp europaea. O DNA das cultivares foi analisado por meio de nove primers SSR pré-selecionados (GAPU59, GAPU71A, GAPU71B, GAPU103A, UDO99-01, UDO99-12, UDO99-28 and UDO99-39) e reveleram um total de 29 alelos que permitiram individualizar cada um dos genótipos. No dendrograma, os nove primers permitiram a separação dos 23 genótipos, em subgrupos. Os SSR foram eficientes e confiaveis para a caracterização molecular de cultivares italianeo de oliva

Climate change effect on the bud break and flowering dates of the apple trees in mountainous and plain regions of Algeria

Global warming is a strongly felt reality in recent years in Algeria. The fruit trees crop is particularly exposed to the impact of this warming, especially apple trees. A comparative study has been realized between a chronological daily temperature series from 1980 to 2016, and phenological data series (budburst and flowering) from 2000 to 2016, regarding the apple tree variety of Golden Delicious in two zones of Northern Algeria, Sidi Lakhdar (town of Ain Defla, in an altitude of 211 m) and Benchicao (town of Médéa, in an altitude of 1133 m). Some contrasting tendencies according to sites and periods have been demonstrated: very significant warming at Sidi Lakhdar site in autumn and spring, in particular in October and April, disturbing thus the entrance of the buds in the endodormancy and ecodormancy. The result is a late action of the cold until February, which proved to be insufficient. However, no average warming has been demonstrated at the Benchicao site, where the temperatures between November and January were cold enough to satisfy the need of cold units and raise the endodormancy. It seems that the failure to fulfill the need of cold units at Sidi Lakhdar site has strongly affected the goodness of fit of the classic phenological models, confirming indirectly the existence of more complex physiological processes (not taken in consideration by models), which manifest themselves in limited zones such as Sidi Lakhdar site

Pollen-mediated gene flow in a highly fragmented landscape: consequences for defining a conservation strategy of the relict Laperrine's olive.

In the present central Saharan conditions, the Laperrine's olive regeneration has never been observed and its populations are locally threatened. The production of plants originating from seeds was proposed as a multiplication strategy. In order to determine the impact of sexual reproduction, seeds issued from ten mothers (sampled from four locations in the Hoggar, Algeria) were genotyped using microsatellites. Compared to the initial population, a significant lost of allelic richness was revealed, indicating that our seed sampling was not representative of the local gene diversity. Paternity analyses allowed measurement of the effective pollen-mediated gene flow within patches. Preferential mating between some genotypes was revealed. A trend for a higher multipaternity on seeds collected on trees from relatively large patches was also observed. Lastly, seedlings issued from trees of small patches displayed low growth performance. The implications of our observations in the development of an efficient conservation strategy by seeds are discussed

Population genetics of Mediterranean and Saharan olives: geographic patterns of differentiation and evidence for early generations of admixture

BACKGROUND & AIMS : The olive (Olea europaea subsp. europaea) was domesticated in the Mediterranean area but its wild relatives are distributed over three continents, from the Mediterranean basin to South Africa and south-western Asia. Recent studies suggested that this crop originated in the Levant while a secondary diversification occurred in most westward areas. A possible contribution of the Saharan subspecies (subsp. laperrinei) has been highlighted, but the data available were too limited to draw definite conclusions. Here, patterns of genetic differentiation in the Mediterranean and Saharan olives are analysed to test for recent admixture between these taxa.[br/] METHODS : Nuclear microsatellite and plastid DNA (ptDNA) data were compiled from previous studies and completed for a sample of 470 cultivars, 390 wild Mediterranean trees and 270 Saharan olives. A network was reconstructed for the ptDNA haplotypes, while a Bayesian clustering method was applied to identify the main gene pools in the data set and then simulate and test for early generations of admixture between Mediterranean and Saharan olives. [br/] KEY RESULTS : Four lineages of ptDNA haplotypes are recognized: three from the Mediterranean basin and one from the Sahara. Only one haplotype, primarily distributed in the Sahara, is shared between laperrinei and europaea. This haplotype is detected once in Dhokar, a cultivar from the Maghreb. Nuclear microsatellites show geographic patterns of genetic differentiation in the Mediterranean olive that reflect the primary origins of cultivars in the Levant, and indicate a high genetic differentiation between europaea and laperrinei. No first-generation hybrid between europaea and laperrinei is detected, but recent, reciprocal admixture between Mediterranean and Saharan subspecies is found in a few accessions, including Dhokar. [br/] CONCLUSIONS : This study reports for the first time admixture between Mediterranean and Saharan olives. Although its contribution remains limited, Laperrines olive has been involved in the diversification of cultivated olives