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Tomato (Lycopersicon esculentum Mill.) are considered major and important globally vegetable crops and in Egypt in particular. Tissue culture techniques have encouraged the utilization of mutation methods in crop improvement. The mutation induction in vegetative crops through tissue culture may be the optimal method to improve these crops. Induced genetic variation in tomato plantlets by using gamma radiation and identified these changes through SCoT and ISSR markers. Egyptian tomato cultivar Idkawy explant was cultured onto MS medium supplemented with 0.2 mg-l BAP. The resulted plantlets were irradiated with γ radiation doses (50, 100, 150, 200 or 250 Gy). The survival, growth rate, and mean of shoot length were decreased with increasing gamma radiation dose. The irradiated plantlets survival percentages were ranged from 78.75% to (50 Gy) and 18.75% to (250 Gy), whereas, the shoot length decreased by a rate of 2.71 cm for the dose (50 Gy) and 1.2 cm for dose (250 Gy). Genetic diversity was evaluated by SCoT and ISSR markers using ten primers for each. It was noticed that the polymorphism percentage mean of SCoT marker (60.53%) is higher than the ISSR marker (39.6). The PIC values average for both markers SCoT and ISSR were 0.429 and 0.347, as well, MI values were 0.345 and 0.156, respectively. On the other hand, the effective no. of alleles (Ne), Nei's genetic diversity (H) and Shannon's information index (I) parameters, it was found that the dose 100 Gy caused the highest genetic variation compared with other doses using SCoT marker, however, in ISSR marker was dose of 150 Gy the highest dose for induced genetic variation. 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. The relationships within treatments were assessed through cluster analysis (UPGMA) based on SCoT and ISSR analysis. [ABSTRACT FROM AUTHOR]

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