To dissect differences in both lipid accumulation and composition and the role of these modifications during drought stress, four grapevine cultivars exhibiting differential tolerance to drought were subjected to water shortage. Tolerant cultivars, Kahli Kerkennah and Cardinal, exhibited higher leaf water potential (Ψ w ), and lower lipid peroxidation compared to the sensitive cultivars Guelb Sardouk and Superior Seedless during stress. Total lipid amounts increased during stress only in the leaves of the tolerant cultivars. Drought induced increases in the ratios digalactosyldiacylglycerol/monogalactosyldiacylglycerol and phosphatidylcholine/phoshatidylethanolamine of almost all the drought stressed cultivars. Moreover, the overall analysis of the composition of fatty acids revealed that a linolenic acid was prevalent in grapevine and the unsaturation level of lipids increased under water stress in all the cultivars. Specific adjustments in the lipid composition during stress could compromise stress tolerance.

No abstract

Leaf anatomical and ultrastructural responses of "Razegui" and "Muscat Italia" grapevine cultivars to high temperatures were studied under controlled conditions (T > 36°C), based on photonic and electron microscopy. Histological studies performed on leaves from heat-stressed and control grapevines revealed thicker leaf blades under high temperature conditions. Environmental scanning electron microscopy of leaf surfaces from both cultivars allowed observing sinuate epidermal cells on the leaves of grapevines cultivated under heat stress and irregular giant oblong pores on their adaxial surface. When observed by transmission electron microscopy, leaf cross sections in grapevines cultivated under high temperature conditions exhibited folded cuticle and cell wall on the adaxial epidermis layer. Therefore, significantly greater cell wall thicknesses were measured under heat stress than control conditions in both cultivars. Regarding chloroplasts, they were more globular in shape under heat stress compared with control conditions and had disorganized thylakoids with a reduced thickness of grana stacking. The size of starch granule decreased, while the number of plastoglobules increased with heat stress, indicating a reduced carbon metabolism and a beginning of senescence within the 3-month heat stress period. This study confirms widespread adaptive properties in two grapevine cultivars in response to high temperature stress.

No abstract

<p style="text-align: justify;"><strong>Aims</strong>: 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.</p><p style="text-align: justify;"><strong>Methods and results</strong>: 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.</p><p style="text-align: justify;"><strong>Conclusion</strong>: 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.</p><p style="text-align: justify;"><strong>Significance and impact of study</strong>: 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.</p>