Molecular Diversity Analysis of in vitro and Irradiated Tomato (Lycopersicon esculentum Mill) Grew Under Salt Stress Expressed by SCoT and ISSR Markers

Tomato buds of cv. Idkawy were cultured in vitro on solid MS medium with 0.2 mg-l BAP. The plantlets that were produced were exposed to different doses of gamma radiation, ranging from 100 to 200 Gy. Afterward, single pieces of nodes were cut and moved to a fresh MS medium with 0.2 mg-l of BAP. The gamma radiation caused a mortality rate of 18.75% to 52.5% among the explants. The surviving plantlets were then cut into single node pieces and transferred to an MS medium containing 0.2 mg-l of BAP, with added NaCl concentrations of either 50 or 100 mM. There was increased mortality of the vegetative buds on the explants with increased salt concentrations. It was shown that the all gamma radiation doses caused reduced the percentage of survival at saline levels. The genetic diversity was assessment by using ten primers for each SCoT and ISSR markers to six irradiated treatments grew under salt stress (100 Gy x 50 mM, 150 Gy x 50 mM, 200 Gy x 50 mM, 100 Gy x 100 mM, 150 Gy x 100 mM, 200 Gy x 100 mM). It was showed that the polymorphism percentage mean of SCoT marker (29.56%) is higher than the ISSR marker (26.78%). The average of PIC values for both markers SCoT and ISSR were 0.197 and 0.288 (PIC ˂0.5), as well as, MI values were 0.077 and 0.081, respectively. In contrast, when considering the number of alleles (Ne), Nei's genetic diversity (H), and Shannon's information index (I) parameters, it was observed that the greatest genetic variation was caused by the combined treatment of 200 Gy x 50 mM NaCl using the SCoT marker. On the other hand, with the ISSR marker, the highest induced genetic variation was seen with the combined treatment of 150 Gy x 50 mM NaCl. The obtained results demonstrate that SCoT marker was more accurate and efficient than ISSR marker for distinguishing and genetic variation analysis of irradiated tomato plantlets grew under salt stress. The relationships within treatments were estimated through cluster analysis (UPGMA) based on SCoT and ISSR analysis.