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

Abstract

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.