Research article differential in vitro direct regeneration of tomato genotypes on various combinations of growth regulators

Abstract

Background and Objective: Tomato {Lycopersicon esculentum L) is one of the most extensively consumed crops. Optimizing the conditions of its in vitro regeneration besides extending the technology to a wider range of cultivars will enhance transformation results.The current study aimed at evaluating the effect of genotype and growth regulators in both of pre-culture and regeneration media on direct shoot regeneration from cotyledonary explants. Attention is particularly given to study of the interaction between the genotype, growth regulators and media type. Materials and Methods: Cotyledonary leaf explants from five tomato genotypes (National Gene Bank's accession numbers, El: 13139, E2:13163, E3:13145, F4:12676 and E5:12702) were cultured on two different pre-culture media (PCM) for 2 days and then sub-cultured on three different shoot induction media (SIM) consisting of Murashig and Skoog (MS) media supplemented with various combinations of growth regulators. Results: SIM3 (MS medium supplemented with 1.0 mg L-1 6-benzylaminopurineand 1.0 mg L-1 zeatin) was the most effective in scoring high regeneration frequency and shoot number as well as the highest shoot length. Although PCM1 (0.5 mg L-1 indol-3-acetic acid and 0.5 mg L-1 kinetin) was less effective in direct regeneration from most of the investigated tomato genotypes, it worked effectively with E3 by exhibiting the highest shoot number (13±0.08) directly regenerated/explant, high shoot length (0.87±0.23 cm) and high regeneration frequency (86%) after transferring to SIM3. The genotype F4 came after E3 by exhibiting high shoot number and length as well as the highest regeneration frequency, in addition to scoring neither callus nor adventitious roots, while El, E2 and E5 were superior in callus induction and adventitious roots. Conclusion:The differential response of the investigated genotypes to the types and combinations of growth regulators depends on the endogenous levels of hormones in the tested tomato genotypes.