Prospecting of local grapevine (Vitis vinifera L.) germplasm revealed that Tunisia possesses a rich patrimony which presents diversified organoleptic characteristics. However, viral diseases seriously affect all local grapevine cultivars which risk a complete extinction. Sanitation programs need to be established to preserve and exploit, as a gene pool, the Tunisian vineyards areas. The presence of the Grapevine leafroll associated virus-3 (GLRaV-3), Grapevine stem pitting associated virus (GRSPaV) and Grapevine virus A (GVA), were confirmed in a Tunisian grapevine cultivar using serological and molecular analyses. The association between GRSPaV and GVA viruses induces more rugose wood symptoms and damages. For this reason the cleansing of the infected cultivar is highly advisable. Direct and recurrent somatic embryos of cv. 'Hencha' were successfully induced from filament, when cultured on Chée and Pool (1987). based-medium, enriched with 2 mg 1-1 of 2,4-dichlorophenoxyacetic acid and 2.5 mg 1-1 of Thidiazuron, after 36 weeks of culture. After six months of acclimatization, RT-PCR carried on 50 somaplants confirmed the absence of GVA, GRSPa-V as well as GLRaV-3 viruses in all somaplants. Ampelographic analysis, based on eight OIV descriptors, was carried out on two years acclimated somaplants, compared to the mother plant. Results demonstrated that the shape and contours of 46 somaclones leaves are identical to mother plant leaves and four phenotypically off-type plants were observed. The healthy state of 100% 'Hencha' somaclones and the high percentage of phenotypically true-to-type plants demonstrate that somatic embryogenesis is a promising technique to adopt for grapevine viruses elimination.

An in vitro protocol has been developed for callus induction, somatic embryogenesis, and plant regeneration in the Barbary fig (Opuntia ficus-indica) cultivars ‘Gialla’ and ‘Moore’. Immature anthers cultivated in the dark on induction medium which consisted of Chée and Pool medium containing 2.0 mg l^–1 2,4-dichlorophenoxyacetic acid (2,4-D) and 2.5 mg l^–1 thidiazuron (TDZ), produced primary nodular and greenish calli within 6 – 8 weeks. Periodic transfer of nodular calli on induction medium in the dark induced the formation of compact embryogenic masses after 4 – 5 months of cultivation, with induction rates of 58.97 ± 1.10% and 61.15 ± 1.16% for ‘Moore’ and ‘Gialla’, respectively. Various distinct stages were observed during the development of somatic embryos on induction medium, including pro-embryogenic, globular, heart-, torpedo-, and cotyledonary-shaped somatic embryos, as well as secondary somatic embryos. Further development of somatic embryos was accomplished using half-strength Murashige and Skoog medium containing 1% (w/v) activated charcoal under a 16-h photoperiod. Bipolarity of the somatic embryos was confirmed by environmental scanning electron microscopy. Regenerated plantlets with well-developed cladodes and roots were transferred to a greenhouse and acclimatised successfully.

Xylem vessels are essential pivotal organs in bulk hydraulic flow through the whole woody plant. However, environmental constraints generate disagreements in xylem structures, which are characterized by air emboli and occlusions formations, compromising water conductivity in grapevines. The aim of this work was to explore xylem morphology dynamics through the xylem sap flow of five Tunisian grapevine cultivars during the natural bleeding sap periods of 2019, 2021, and 2022. In fact, Sakasly, Khamri, Hencha, Razegui1, and Razegui2 rain-fed grapevine cultivars revealed differential responses towards xylem sap movement. The results demonstrated that the xylem sap flow was significantly more abundant in 2019 than 2021 and 2022 bleeding sap campaigns. A variation was revealed between the cultivars regarding the xylem sap flow. In fact, Sakasly gave the best xylem flow during the three campaigns. Razegui1 and Razegui2 registered approximately similar xylem sap flow, while Hencha and Khamri present the lowest sap fluxes during the three campaigns. Moreover, several vascular occlusions forms were identified from stem cross sections using environmental scanning electron microscopy (ESEM), including tyloses, gels, starch, and gum deposits. The highest occlusion number was observed in Sakasly, Razegui1, and Razegui2 cultivars. Among different biogenic calcium shapes, several were observed for the first time in grapevine, including multi-faceted druse, cubic, crystalline sand, styloids, spherical, or drop-like structures. Considering their lower flow and totally blocked vessels, both Hencha and Khamri confirmed their susceptibility to environmental constraints. However, Sakasly, Razegui1, and Razegui2 cultivars presented higher tolerance according to their sap flow and xylem morphology.

Aims: The aim of this research is to identify the optimal flower developmental stage, in order to establish an efficient regeneration protocol via somatic embryogenesis in several local grapevine (Vitis vinifera L.) cultivars, using anther culture.Methods and results: Immature anthers sampled on fruity cuttings, at three flower developmental stages were cultured on three media [MS (1962), NN (1969) and CP (1987)] to which several phytohormonal combinations were added. Anthers, sampled at the « separated floral buds » stage, corresponding to the tetrad stage of microsporogenesis revealed to be the most appropriate for somatic embryogenesis compared to anthers sampled at the « separated clusters » and « early bloom » stages. Therefore, a unique medium, CP (1987) supplemented with 9 μM of 2,4-D and 11.35 μM of thidiazuron was established for the induction as well as the development of somatic embryos.Conclusion: The identification of an appropriate flower developmental stage and the optimization of a unique medium allowed establishing a reliable and repetitive regeneration system via somatic embryogenesis, in several local grapevine cultivars.Significance and impact of study: These embryogenic lines would be particularly appropriate as a target for the genetic transformation, directed towards the induction of tolerance to several biotic and abiotic stresses as well as for bioprospecting.