Genotypic study of Tunisian Arabian stallions

Diversity of Arabian stallions distributed throughout the territory of Tunisia has been evaluated. Seventeen microsatellite markers were used for the determination of genetic variation. A total of 95 alleles were detected in the 50 stallions studied. The number of alleles per locus ranged from 2 to 9 with an average of 5.6. The observed mean number of genetically diverse alleles (Na) was 5.6 (0.44). The mean number of expected alleles (Ne) was 3.42 (0.28). The average expected and observed heterozygosity was approximately 0.675 (0.026) and 0.593 (0.044), respectively. Principal component analysis showed the presence of 2 subpopulations in the studied sample set. These findings demonstrate the potential of microsatellites as a tool for designing and controlling animal breeds. Results show that the population under study has sufficient levels of genetic variations, which can be used as a foundation for developing plans for species conservation and long-term sustainability

Viroid infection and rootstocks affect productivity and fruit quality of the Tunisian citrus cultivar Maltaise demi sanguine

In Tunisia, sweet orange citrus cultivars are usually grafted on sour orange rootstock. However, this rootstock is susceptible to Citrus tristeza virus (CTV). A trial was established in 2005 to evaluate the performance of newly introduced rootstocks compared to sour orange, using the sweet orange cultivar ‘Maltaise demi sanguine’ as the grafted scion. The effect of single or mixed viroid infections were monitored over 12 years. Once established, tree growth, cumulative yield, tree performance and fruit quality of ‘Maltaise sweet orange’ were assessed from 2008. Mixed viroid infections caused significant decreases (39 to 60%) in the canopy volume of ‘Maltaise’ grafted on Carrizo citrange, Swingle citrumelo, Cleopatra mandarin, Rangpur lime, Volkamer lemon and Trifoliate orange. The cumulative yield of trees grafted on’Alemow’ (Citrus macrophylla) and inoculated with Hop stunt viroid (HSVd) was 76% less than the healthy control. Mixed infections caused production decreases of 56% from trees grafted on Swingle citrumelo and 69% from those grafeted on Trifoliate orange. When quality parameters of fruit from trees infected with each viroid, and combinations of viroids were compared, no significant differences were recorded.

Viroid infection and rootstocks affect productivity and fruit quality of the Tunisian citrus cultivar Maltaise demi sanguine

In Tunisia, sweet orange citrus cultivars are usually grafted on sour orange rootstock. However, this rootstock is susceptible to Citrus tristeza virus (CTV). A trial was established in 2005 to evaluate the performance of newly introduced rootstocks compared to sour orange, using the sweet orange cultivar ‘Maltaise demi sanguine’ as the grafted scion. The effect of single or mixed viroid infections were monitored over 12 years. Once established, tree growth, cumulative yield, tree performance and fruit quality of ‘Maltaise sweet orange’ were assessed from 2008. Mixed viroid infections caused significant decreases (39 to 60%) in the canopy volume of ‘Maltaise’ grafted on Carrizo citrange, Swingle citrumelo, Cleopatra mandarin, Rangpur lime, Volkamer lemon and Trifoliate orange. The cumulative yield of trees grafted on’Alemow’ (Citrus macrophylla) and inoculated with Hop stunt viroid (HSVd) was 76% less than the healthy control. Mixed infections caused production decreases of 56% from trees grafted on Swingle citrumelo and 69% from those grafeted on Trifoliate orange. When quality parameters of fruit from trees infected with each viroid, and combinations of viroids were compared, no significant differences were recorded.

Genetic diversity in Tunisian horse breeds

This study aimed at screening genetic diversity and differentiation in four horse breeds raised in Tunisia, the Barb, Arab-Barb, Arabian, and English Thoroughbred breeds. A total of 200 blood samples (50 for each breed) were collected from the jugular veins of animals, and genomic DNA was extracted. The analysis of the genetic structure was carried out using a panel of 16 microsatellite loci. Results showed that all studied microsatellite markers were highly polymorphic in all breeds. Overall, a total of 147 alleles were detected using the 16 microsatellite loci. The average number of alleles per locus was 7.52 (0.49), 7.35 (0.54), 6.3 (0.44), and 6 (0.38) for the Arab-Barb, Barb, Arabian, and English Thoroughbred breeds, respectively. The observed heterozygosities ranged from 0.63 (0.03) in the English Thoroughbred to 0.72 in the Arab-Barb breeds, whereas the expected heterozygosities were between 0.68 (0.02) in the English Thoroughbred and 0.73 in the Barb breeds. All FST values calculated by pairwise breed combinations were significantly different from zero (p  <  0.05) and an important genetic differentiation among breeds was revealed. Genetic distances, the factorial correspondence, and principal coordinate analyses showed that the important amount of genetic variation was within population. These results may facilitate conservation programs for the studied breeds and enhance preserve their genetic diversity

Comportemement végétatif et génératif de plants de Fraisier (Fragaria x ananassa Duch.) issus de la régénération in vitro à partir de bourgeons axillaires ou stipulaires

peer reviewedIn vitro regeneration of strawberry (Fragaria x ananassa Duch.) plants from adventitious stipular buds allowed us to obtain a new clone differing from the axillary originated clone by its vegetative and reproductive behavior. Besides of its clear and rounded leaves, this clone is characterized by a slower plastochronal rythm corresponding to the production of a greater number of axillary shoots (runners). Furthermore, its flowers have shorter receptacle that does not overstep stamens. At the contrary, receptacle of the axillary clone largely overstep stamens and then, they are not well pollinated and resulted in malformed fruits especially in cold season or in absence of pollen vectors.La régénération in vitro de plants de fraisier (Fragaria x ananassa Duch. cv. Elsanta) à partir de bourgeons adventifs stipulaires était à l’origine de l’obtention d’un clone dont le comportement végétatif et reproducteur in vivo s’est nettement distingué de celui de son homologue d’origine axillaire. Hormis la couleur claire et la forme arrondie de ses feuilles, ce nouveau clone se caractérise par un rythme plastochronal plus lent qui correspond aussi à la production d’un plus grand nombre de bourgeons axillaires sous forme de stolons. Au niveau floral, le réceptacle est moins allongé et se trouve à la hauteur des étamines dont les anthères sont plus volumineuses que celles du clone axillaire. Ce dernier dont le réceptacle émerge au delà des étamines présente une moins bonne pollinisation qui se traduit par une importante déformation des fruits surtout en hiver et en l’absence d’agents pollinisateurs

Morphological and hormonal characterisation of strawberry vitroplants raised through axillary or stipular adventitious shooting

peer reviewedAdventitious stipular bud formation occurred in vitro in many strawberry cultivars during the proliferation phase on medium containing Knop macronutrients, MS micronutrients, vitamins, aminoacids, 2.22 muM BAP, 2.46 muM IBA and 0.29 muM GA(3). As described previously for cultivar Gorella, cultivar Elsanta also showed adventitious stipular buds developing on the abaxial median zone between the stipule tips. To compare the shoots produced from both types of buds, clonal propagation was initiated from stipular buds and from axillary buds on the above mentioned medium. Stipular buds were separated from the meristem-tip initiated plantlet and cultivated in the presence of a lower BAP concentration (1.33 muM) to prevent further stipular bud formation. During proliferation cycles, stipular originated propagules were very easily distinguished by their specific leaf phenotype and light green colour in comparison to plantlets cloned for an axillary bud. Their multiplication rate and cytokinin content were also higher than for axillary buds. No significant difference was observed in auxin content

Effet du nitrate d’ammonium sur le développement et l’activité des enzymes anti-oxydantes du fraisier (Fragaria x ananassa L.) micropropagé

Effect of ammonium nitrate on the development and anti-oxydant enzymes activity of strawberry (Fragaria x ananassa L.) propagated in vitro. The addition of ammonium nitrate (NH4NO3) at different concentrations (500, 1000 and 1500 mg.l-1) to the in vitro multiplication medium improved significantly the vigor and reversed the leaf chlorosis affecting the strawberry shoots when cultivated on Boxus standard medium, which only contains nitrate as source of nitrogen. The analysis performed with both susceptible « Chandler » and more tolerant « Sweet Charlee » varieties showed that NH4NO3 would confer a more favorable and less stressful nutritional situation to the vitroshoots. Higher quantity of total soluble proteins and improvement of CAT and POD enzymatic activities in both varieties are the single changes observed in the metabolism of the shoots cultivated in presence of ammonium nitrate. This situation allowed those shoots to protect their membrane lipids against peroxydation due to a better activity of their anti-oxidant enzymes

Adventitious organogenesis induced in sweet orange (Citrus sinensis L.) var. "half-blood" maltese: morphogenetic and histological study

peer reviewedTunisian citrus crops are faced to several abiotic and biotic constraints among which virus and virus-like diseases are incurable. The production of virus-free plants systematically needs the use of in vitro techniques. In this context, somatic embryogenesis and further plantlet regeneration of the Tunisian “half-blood” Maltese orange were obtained using explants consisting in style/stigma collected from unopened flowers. Somatic embryos were induced on Murashige and Skoog medium containing 13.3 µM 6-benzylaminopurine and 500 mg.l-1 malt extract, but their germination was obtained on hormone free-medium. Somatic embryogenesis was induced indirectly from intermediate friable callus initiated at the basal part of the style. Somatic embryos exhibited central procambial cells and were surrounded by a protoderm isolating them from the callus. These embryos had bipolar structure confirmed by the presence of shoot and root apices at cotyledonary stage. The use of cotyledon excised from those embryos failed to regenerate somatic embryos, but gave rise to direct organogenesis in two forms, true buds and protuberances both evolved in shoots after transfer in hormone-free medium. According to histological observations, protuberances are induced from epidermal and subepidermal cells of the cotyledon explant and remain closely attached to their mother tissue even at the shoot stage