Responses of two strawberry cultivars to NaCl-induced salt stress under the influence of ZnO nanoparticles.

Salinity stress is one of the most serious impacts of climate changes on agriculture production, especially in salt sensitive crop plants, like strawberry. Currently, the utilization of nanomolecules in agriculture is thought to be a useful strategy to compact abiotic and biotic stresses. This study aimed to investigate the effect of zinc oxide nanoparticles (ZnO-NPs) on the in vitro growth, ions uptake, biochemical and anatomical responses of two strawberry cvs (Camarosa and Sweet Charlie) under NaCl-induced salt stress. A 2x3x3 factorial experiment was conducted, with three levels of ZnO-NPs (0, 15 and 30 mg 1-l) and three levels of NaCl-induced salt stress (0, 35 and 70 mM). The results showed that increased levels of NaCl in the medium had led to decrease in shoot fresh weight and proliferative potential. The cv Camarosa was found to be relatively more tolerant to salt stress. Additionally, salt stress leads to an accumulation of toxic ions (Na + and Cl-), as well as a decrease in K + uptake. However, application of ZnO-NPs at a concentration of 15 mg 1-l was found to alleviate these effects by increasing or stabilizing growth traits, decreasing the accumulation of toxic ions and the Na+/K + ratio, and increasing K + uptake. Additionally, this treatment led to elevated levels of catalase (CAT), peroxidase (POD) and proline content. The positive impacts of ZnO-NPs application were reflected on the leaf anatomical features, being better adapted to salt stress. The study highlighted the efficiency of utilizing tissue culture technique in screening of strawberry cultivars for salinity tolerance under the influence of NPs.

Somatic embryo-like structures of strawberry regenerated in vitro on media supplemented with 2,4-D and BAP.

Somatic embryo-like structures (SELS) were produced in vitro from leaf disk and petiole explants of two cultivars of strawberry (Fragaria x ananassa Duch) on Murashige and Skoog medium with different concentrations and combinations of 2,4-dichlorophenoxyacetic acid (2,4-D), 6-benzylaminopurine (BAP) and sucrose to check the embryonic nature of these structures histologically. A large number of SELS could be regenerated in both cultivars on media with 2-4 mg L(-1) 2,4-D in combination with 0.5 -1 mg L(-1) BAP and 50 g x L(-1) sucrose. Histological examination of SELS revealed the absence of a root pole. Therefore these structures cannot be strictly classified as somatic embryos. The SELS formed under the tested culture conditions represent malformed shoot-like and leaf-like structures. The importance of these results for the propagation of strawberries via somatic embryogenesis is discussed.

High frequency, direct shoot regeneration from greenhouse-derived leaf disks of six strawberry cultivars.

Leaf disks derived from either two-month-old GreenHouse-grown (GHD) strawberry plants or in vitro plantlets were cultured on MS media amended with 2 mg L(-1) Thidiazuron (TDZ), incubated for four weeks in the dark then for another four weeks under 16/8 h light regime. Regeneration capacity of leaf disks was compared to meristem-derived propagules in six strawberry cultivars. Direct shoot regeneration occurred in all tested cultivars with different frequencies depending on explant source. From GDH leaf disks, the cultivars Camarosa, Gaviota and Seascape produced the highest number of shoots/explant (38, 31 and 31 shoots, respectively). However, optimum number of shoots/explant from in vitro leaf disks was achieved in the cultivars Carlsbad, Chandler and Sweet Charlie (13.3, 12.6 and 12.3 shoots, respectively). In general, regeneration capacity of GHD leaf discs was more than two-folds of that obtained from in vitro leaf disks. The efficiency of meristem culture was intermediate between the above two systems. Rooted plantlets were successfully acclimatized under mist. The only morphological abnormality detected was a white streaked variant observed out of 456 Camarosa plants derived from meristem culture. SDS-PAGE of protein profile proved consistency in banding patterns of mother plants and those derived from direct regeneration or meristem proliferation.