Negative impact of drought stress has been recognized to pose a growing threat to sustainable agriculture particularly under the global climate change. The main goal of this research was to develop an effective protocol for regenerating drought tolerant peanut plants. Specific objectives were to select drought tolerant embryogenic calli (EC), on a medium containing polyethylene glycol (PEG), and evaluate the regenerated lines against drought stress environment. Somaclones were selected through continuous culture of EC for 6 months on MS-P16 medium. The EC were sub-cultured onto the fresh MS-P16 medium every month. In vitro drought tolerant somatic embryos (SE) were selected on MS-P16 medium containing 15% PEG 6000. PEG tolerant SEs were regenerated (R0 plantlets) and grown to maturity in the greenhouse to produce R1 seeds. Subsequently, these seeds were planted to maturity to produce R2 seeds. The R2 plants were subjected to drought stress by reduced watering under greenhouse conditions and their growth parameters and yield were recorded. Results showed plants regenerated from 6-month-old EC cultures exhibited variations in plant height, fresh and dry weight of above ground biomass and of the roots, total pod and filled (matured) pod yield at harvest. The majority (56-100%) of the EC did not survive the in-vitro selection on MS-P16 containing 15% PEG. However, some newly regenerated SEs developed from mostly browning tissues on the same medium. Peanut plants were regenerated from these SEs and the R1 and R2 plants derived from these somatic embryos were obtained. Among evaluated R2 plants regenerated from PEG stress tolerant SEs, 44% plants exhibited drought tolerance under greenhouse conditions.
Key words: Drought stress, dehydration stress, PEG stress tolerance, somatic embryo, somaclonal variant, Arachis hypogaea