In Vitro Selection of Calli for Salt Tolerance in Tomato (Solanum lycopersicum L.)

Soil salinity is one of the most important abiotic stresses that limit crop production. Responses of six breeding lines (BD-7755, BD-7757, BD-9008, BD-9011, BD-10122, BD-10123 which were named as G1, G2, G3, G4, G5 and G6 respectively) of tomato (Solanum lycopersicum L) to NaCl stress were studied in callus induction. Hypocotyl and cotyledon segments were chosen as explants for callus induction in vitro. The six investigated tomato genotypes differed in their callus growth. Tomato seeds were cultured for callus formation and that callus were treated with 0 mM (control), 50 mM, 100 mM, 150 mM and 200 mM NaCl in nutrient solutions. The effect of the stress applied on the callus was evaluated in 10 DAT (Days After Treatment) and 17 DAT. Different concentrations of NaCl in the medium significantly affected the biomass callus size and callus weight of tomato. G2 and G6 showed excellent performance of tolerance up to 50 mM of NaCl. G6 showed better performance under high salt concentrations i.e., at 100 mM and 200 mM but not at low salt stress. It indicates the expression of functional gene occurs at high salt stress. However it is possible to select callus line tolerant to elevated levels of NaCl stress by sudden exposure to high of NaCl, accordingly a NaCl tolerant cell line was selected from hypocotyls and cotyledon derived callus of tomato which proved to be a true cell line variant. The interaction effect of variety and treatmentrevealed that genotype G6 and G1 were the highest and lowest performer respectively. These findings indicated some salt tolerant tomato genotypes which will be promising for regeneration and for future breeding program. It is quiet necessary to asses accumulation of proline and the anti-oxidant enzymes like Super Oxide Dismutase, Ascorbate Peroxidase and Catalase from the control and stressed callus as they are the indicator of salt tolerance. It is evident that tissue culture technique was able to evaluate several genotypes for salt tolerance into cell level under controlled environment with relatively little space and less time required comparing with such process studies at the whole plant level