Molecular characterization and genetic relationships among most common identified morphotypes of critically endangered rare Moroccan species Argania spinosa (Sapotaceae) using RAPD and SSR markers

? The objective of this work is the molecular characterization of most common identified morphotypes of critically endangered rare Moroccan species Argania spinosa.

? Eighteen RAPD markers and twenty SSR markers have been assayed in 38 argan tree accessions from the three most commonly identified morphotypes: oval, spherical and spindle fruit types.

? A total of 140 polymorphic RAPD bands were detected out of 146 bands. The number of presumed alleles revealed by the SSR analysis ranged from 1 to 5 alleles per locus with a total number of 32 alleles identified. Results demonstrated an extensive genetic variability within the tested argan accessions. RAPDs presented a high level of polymorphism and greater information content than SSRs.

? Our results could indicate that Vitellaria paradoxa is genetically closer to argan than Manilkara huberi. In addition, the correlation between the clustering based on RAPD and SSR markers were in general low. The observed clustering could be better explained according to geographic proximity than morphotype. For this reason the traditional morphological characterization of the argan accessions in morphotypes (according to fruit phenotype) seem not to be in correlation to the real genetic background (genotype) of this specie. The implications of these results in the creation of effective germplasm core collection in argan have been also discussed.

     

Gene flow among wild and cultivated common walnut (Juglans regia) trees in the Qinling Mountains revealed by microsatellite markers

Patterns of gene flow and gene introgres sion can be used to assess the risk of genetic pollution of wild forest trees from widespread cultivated trees.A comprehensive understanding of the genetic relationships and levels of gene flow among wild and cultivated common walnut(Juglans regia) has become an urgent issue.Using twelve microsatellite markers,we investigated the genetic diversity and gene flow between cultivated and wild trees of J.regia in the Qinling Mountains,China.A high level of genetic variation was detected in both cultivated and wild trees.The mean number of alleles per locus was 17.5.Observed heterozygosity(H_O)and expected heterozygosity(H_E) were 0.777 and 0.800,respectively.Pollination of mother trees was not by nearest neighbors,and a paternity of 60.7% of offspring evaluated could not be assigned to a local,sampled tree.Pollen flow from cultivated trees to wild trees was infrequent(5.4%),and selfing rates ranged from zero to 25.0%.Male parents were located from 0 to 1005 m from their female partners,with an average pollination distance of 285.1 m.These results are discussed in light of the cultivated species' diversity,outlining the frequent spontaneous genetic contributions from the wild to the cultivated compartment.In addition,the pollen flow parameters provide useful information about the dynamics of pollen movement within J.regia populations.     

Genetic variation within and between populations of a desert poplar (<Emphasis Type="Italic">Populus euphratica</Emphasis>) revealed by SSR markers

Backgroud   

Populus euphratica Oliv., a long-lived woody perennial plant, is the only forest species naturally distributed in desert regions. Severe desertification has resulted in this species becoming endangered, and its populations are seriously fragmented in northwest China.     

Growth and reproductive characteristics of the columnar cactus Stenocereus queretaroensis and their relationships with environmental factors and colonization by arbuscular mycorrhizae

Three natural populations of pitayo (Stenocereus queretaroensis (Weber) Buxbaum), a columnar arborescent cactus, were studied in their subtropical environments in western Mexico. All of the sites were characterized by shallow, nutrient-poor soils. Percentage of colonization by arbuscular mycorrhizae (AM) fungi, stem growth, fruit mass, and percentage germination were greater in S. queretaroensis at Autlan, Jalisco (AJ) than at Zacoalco de Torres, Jalisco (ZTJ) or Santa Rosa, Zacatecas (SRZ). The onset of root colonization by arbuscular mycorrhizae during the middle of the summer wet period preceded increases in stem extension rate and stem phosphorus concentration. Based on previous studies of effects of environmental factors on photosynthesis, climatic conditions were more favorable for photosynthesis at AJ than at SRZ and ZTJ, as indicated by the amount of summer rainfall, the amount of light, and the moderate air temperatures that prevailed during the fall and winter seasons. There was a significant positive correlation between stem growth and percentage of total root length colonized by arbuscules of AM fungi for S. queretaroensis at SRZ and AJ, but not at ZTJ. A negative significant correlation was observed between stem growth and maximal and minimal air temperatures at the three study sites. Stem growth was positively related to rainfall only at SRZ, and light was statistically related to stem growth only at ZTJ. Among sites, S. queretaroensis at AJ had the highest carbon gain and greatest AM colonization, creating physiological conditions that led to the highest stem growth, fruit mass and percentage of seed germination.