In vitro Variability of Morphogenetic Responses of Tomato (Lycopersicon esculentum Mill.) Explants under Salt Stress and Thidiazuron as Plant Growth Regulator

Abstract

For the present investigation, six genotypes of tomato (Lycopersicon esculentum Mill.) widely grown in Algeria were selected and used as research material to study the morphogenetic variability under stress conditions using different media treatments and two types of explants (cotyledons and hypocotyls) in order to evaluate their responses to callus induction, embryos production and caullogenic capacity. In vitro growth seedlings aged for 21 days old were used as source of explants. These explants were cultivated into a MS-based medium containing a constant concentration of TDZ (3mg/L) used as Cytokinins PGR, combined or not with four increasing levels of NaCl at 0, 25, 50 and 75 mM for eight weeks. This Cytokinins predisposes the explant to stress. Statistical analysis indicated a highly significant variations in responses according the nature of genotype, treatment medium, explant origin and interactions there of possess ample influence on morphogenetic characters under these conditions. Results showed that the morphogenesis responses seems to be dependent NaCl levels added in the media, a moderate concentrations including 25 and 50 mM induces compared to control medium. Whereas, medium MT3 had shown a relative to poor response for the most genotypes tested. It is interesting that the moderate combination NaCl/TDZ was better for the embryos production, which can be used directly or converted into artificial seeds for propagation of high value hybrid. All most every tested explant were differentiated into callus but the favorite explant for carried a research on the variability under stress conditions and embryogenic capacity is the cotyledon. Differences among genotypes were detected. For all effects analyzed, homogeneous groups were established using Newman-Keuls post-hot test. This attempt may be used as efficient protocol for genetic improvement and the use of combination PGRs / Stressor agent could be the option for the somatic embryogenesis investigations.

Keywords

• Salt stress, Cytokinins, Organogenesis, Somatic Embryogenesis