<i>In Vitro</i>Germination and Early Vegetative Growth of Five Tomato (<i>Solanum lycopersicum</i>L.) Varieties under Salt Stress Conditions

In Senegal, tomato (Solanum lycopersicum L.) cultivation is affected by salinity in many agro-ecological zones. The selection of salt tolerant varieties would be an alternative solution to enhance the production. Thus, germination and growth are studied under axenic conditions for five varieties of tomato subjected to increasing concentrations of NaCl [0, 35, 70 and 105 mM], and supplemented in an MS/2 medium for 30 days. The results reveal that salt negatively affects the evaluated parameters. The Rodeo and Lady Nema varieties have the lowest final germination rates (50%) unlike the Mongal variety (55%). These last two varieties have a decrease of 71.78% and 81.28% in the height of the stem, respectively, in the presence of NaCl at [105 mM] while that of the Rodeo variety is 70%. The Xewel variety has the greatest average number of leaves in the presence of [NaCl 35 mM] (4.95 leaves) and [NaCl 70 mM] (4.77 leaves). The Lady Nema variety records the longest taproot length (2.99 cm) unlike the Rodeo variety (2.25 cm) at [NaCl 105 mM]. The Ganila variety reveals the highest number of secondary roots at the concentrations of [0, 35 and 105 mM] of NaCl with, respectively, 44.12, 29.25, and 4.25 roots. The Lady Nema variety records the highest fresh weight of aerial (0.055 g) and root parts (0.014 g) and the lowest root dry weights (0.0023 g). These results allow to conclude that the Lady Nema and Mongal varieties seem more tolerant, Ganila and Xewel are moderately tolerant and Rodeo is more sensitive to the presence of salt.

<i>In Vitro</i>Germination and Early Vegetative Growth of Five Tomato (<i>Solanum lycopersicum</i>L.) Varieties under Water Stress Conditions

Water is the main limiting factor in the cultivation of tomato (Solanum lycopersicum L.) in Senegal. Thus, the selection of varieties tolerant to water stress would be an alternative solution for their production. In vitro germination, growth, total chlorophyll and proline levels were studied in five varieties of tomato subjected to increasing osmotic pressures (0, 5, 10 and 15 kPa) thanks to the PEG-8000 incorporated in an MS/2 medium for 30 days. A strong sensitivity to water stress for in vitro seed germination in the Rodeo variety (41%) is recorded at 5 kPa and maintained at 15 kPa (20.83%) while it was only noticed at 15 kPa in the other tomato varieties. The Xewel and Lady Nema varieties obtained the smallest reductions in the number of leaves of vitroplants, with 30.79% and 27.97% at 15 kPa, respectively, and the Rodeo variety recorded a reduction of 35.97%. From 5 kPa, the varieties record reductions in the number of secondary roots of more than 15%. The effect of osmotic pressures on decreasing the taproot height and length is not significant. The Xewel variety had the highest average fresh (0.483 g) and dry (0.082 g) weights of the aerial part at 15 kPa and the Rodeo variety had the lowest ones (0.308 g and 0.0501 g). The Lady Nema variety had the highest average fresh (0.171 g) and dry (0.039 g) root weights and the Rodeo variety had the lowest ones (0.086 and 0.020 g). The vitroplants of Rodeo variety recorded the highest decreases in total chlorophyll contents at all osmotic pressures and the lowest increase in proline content (53.37%) at 15 kPa. A contrario, the Xewel variety recorded the greatest increase in proline content (116.26%). Ultimately, the vitroplants of Lady Nema and Xewel varieties were more tolerant to water stress, the Ganila and Mongal varieties were moderately tolerant and the Rodeo variety was the most sensitive.

Influence of the Size of Potato Microtubers (<i>Solanum tuberosum</i>L.) on the Yield of Plants under Semi-Axenic Conditions

The potato (Solanum tuberosum L.) is a vegetable that ranks fifth in the world for human consumption. Its importance is growing more and more in the Senegalese diet. However, the potato production in Senegal does not meet the needs of the market, which maintains dependence on the outside for the supply of quality seeds. In addition, these imported seeds do not often have phytosanitary qualities required for local production in the Sahelian zone. The in vitro production of microtubers, used as seed, has been shown to be one of the most efficient means for propagation of basic material. To overcome the constraints linked to the supply and availability of potato seeds, with high germination capacity, the impact of the microtuber size on the yield of the plants under semi-controlled conditions was examined. The pre-germinated microtubers were produced in vitro from vitroplants of 3 different varieties (Aida, Atlas, Odessa) adapted to the edaphic-climatic conditions of Senegal. The effects of the seed sizes of microtubers, greater than 4 mm, sown under semi-controlled conditions, on the yield of the plants, result in an increase in the ratio, in the vegetative development of the plants, but also in the number and size of the minitubers harvested. The yield of the plants also depends on the variety. It can therefore be envisaged to produce local potato seeds from microtubers and minitubers.

Inoculation with arbuscular mycorrhizal fungi improves seedlings growth of two sahelian date palm cultivars (<i>Phoenix dactylifera</i>L., cv. Nakhla hamra and cv. Tijib) under salinity stresses

This study presents an analysis of the impact of mycorrhizal inoculation on growth under salt stress of date palms cultivars Nakhla hamra (NHH) and Tijib known in the Sahel for their earliness in flowering and fruiting. The seedlings were grown in a greenhouse on a sandy substrate watered to field capacity every two days and were subjected to increasing levels of NaCl (0, 1, 2, 4, 6, 8 and 16 g·L-1) and then inoculated with 5 strains of Glomus (G. aggregatum, G. intraradices, G. verriculosum, G. mosseae, G. fasciculatum). The experimental design was a randomized complete block with three factors (cultivars: Tijib and Nakhla Hamra x seven levels of NaCl concentrations x six levels of inoculum). The results showed that in the absence of NaCl, G. verriculosum significantly enhanced shoot growth: 33.5 cm against 30.3 cm in the control and roots growth: 81.5 cm against 78 cm in NHH, while in Tijib, the growth is stimulated by Glomus fasciculatum: 33.8 cm against 32.7 cm for stems and 90 cm against 86 cm for the roots of inoculated plants and controls. In contrast, in the presence of NaCl 8 g·L-1, NHH has a better growth in the presence of G. intraradices: 37.3 cm against 30.6 cm for stems and 77 cm against 73 for roots, while Tijib grows better in the presence of G. fasciculatum with respectively 31.9 cm against 31.7 cm and 51.27 cm against 51.6 cm for stems and roots of inoculated plants and controls. Biochemical analysis revealed that changes in levels of proline depend on the cultivar, the mycorrhizal strain used and concentrations of NaCl applied. These results open the prospect of using mycorrhizal fungi to improve the productivity of palm trees in the Sahel.