Impact of application of zinc oxide nanoparticles on callus induction, plant regeneration, element content and antioxidant enzyme activity in tomato (Solanum lycopersicum MILL) under salt stress

The properties of nanomaterials and their potential applications have been given considerable attention by researchers in various fields, especially agricultural biotechnology. However, not much has been done to evaluate the role or effect of zinc oxide nanoparticles (ZnO-NP) in regulating physiological and biochemical processes in response to salt-induced stress. For this purpose, some callus growth traits, plant regeneration rate, mineral element (sodium, potassium, phosphorous and nitrogen) contents and changes in the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPX) in tissues of five tomato cultivars were investigated in a callus culture exposed to elevated concentrations of salt (3.0 and 6.0 g L-1NaCl), and in the presence of zinc oxide nanoparticles (15 and 30 mg L-1). The relative callus growth rate was inhibited by 3.0 g L-1 NaCl; this was increased dramatically at 6.0 g L-1. Increasing exposure to NaCl was associated with a significantly higher sodium content and SOD and GPX activities. Zinc oxide nanoparticles mitigated the effects of NaCl, and in this application of lower concentrations (15 mg L-1) was more effective than a higher concentration (30 mg L-1). This finding indicates that zinc oxide nanoparticles should be investigated further as a potential anti-stress agent in crop production. Different tomato cultivars showed different degrees of tolerance to salinity in the presence of ZnO-NP. The cultivars Edkawy, followed by Sandpoint, were less affected by salt stress than the cultivar Anna Aasa

Agrobacterium mediated transformation of anti-stress genes into cauliflower (Brassica oleracea var. botrytis L.). 2. Transformation and confirmation of stress tolerance.

Integration of APX and SOD anti-stress genes into cauliflower (Brassica oleracea var. botrytis L.) plants was achieved by using Agrobacterium tumefaciens - mediated transformation method. Cauliflower explants (hypocotyls and cotyledons) and Agrobacterium tumefaciens strains (APX, SA, TA) were used in this experiment. The procedure utilizes polymerase chain reaction (PCR) amplification of insert DNA directly after isolation of individual colonies without the necessity of separate procedures for DNA isolation and purification. Integration of the introduced stress gene (APX and SOD) in the plants was confirmed by using β-glucuronidase gene (GUS) and leaf disc assays as a gene fusion and diagnostic marker, respectively. The stable integration of the APX and SOD gene at 478 bp was detected by using polymerase chain reaction (PCR) of the putative transgenic plants. Analysis of APX and SOD gene expression under salt treatment showed that putative transgenic cauliflower survived the salinity stress comparing with the control plants

Evaluation of abiotic stress resistance in mutated populations of cauliflower (Brassica oleracea var. Botrytis)

An efficient in vitro screening method has been developed for cauliflower to create NEU and NMU induced mutant lines selected on hydroxyproline containing medium. Mutant lines and control plants were sub-cultured many times on maintenance medium and stored at 5°C for 2 years and then tested for salt and hydroxyproline resistance as in vitro and in vivo plants. In vitro shoot tips were also sub-cultured to media containing hydroxyproline and NaCl for 28 days and then assessed for their leaf proline content. Non-acclimated and acclimated in vivo plants were also assessed for resistance to freezing. Populations of control and selected lines were created by mass pollination and subsequently tested for their NaCl and frost resistance. Control plants had little or no NaCl or hydroxyproline resistance whilst selected plants showed varying degrees of resistance. In vitro and in vivo responses of selected lines were correlated. Leaf proline content was increased markedly in the mutant lines and the greatest proline contents occurred following NaCl stress with the most respondent line having 100-fold levels compared to the controls. Both non-acclimated and acclimated selected lines showed improved frost resistance over controls. Improvements in frost resistance were heritable but improvements in NaCl resistance were not. The results clearly demonstrated that NaCl, frost and hydroxyproline resistance were stable traits over repeated in vitro sub-cultures and prolonged low temperature storage. A complete range of mutants with single, double or triple resistance traits were produced. The level of resistance however was not necessarily correlated with the level of proline and some lines showed resistance without elevated proline. It is concluded that elevated proline is not essential for improved resistance to abiotic stress in cauliflower, but where it does occur it does improve resistance. © Springer Science+Business Media B.V. 2006