Shah et al., J. Anim. Plant Sci. 25(2):2015 528 CALLUS INDUCTION, IN VITRO SHOOT REGENERATION AND HAIRY ROOT FORMATION BY THE ASSESSMENT OF VARIOUS PLANT GROWTH REGULATORS IN TOMATO (Solanum lycopersicum Mill.) S. H. Shah * , S. Ali ** , S. A. Jan ** , J. Din *** and G. M. Ali ** * PARC Institute of Advanced Studies in Agriculture (PIASA), National Agricultural Research Centre (NARC), Islamabad-Pakistan & Gomal Centre of Biochemistry and Biotechnology Gomal University, D.I.Khan-Pakistan ** National Institute for Genomics & Advanced Biotechnology (NIGAB), National Agricultural Research Centre (NARC), Islamabad-Pakistan *** Plant Physiology Program, National Agricultural Research Centre (NARC) Islamabad- Pakistan * Corresponding author: sabir_narc1@yahoo.com ABSTRACT In vitro morphogenesis is greatly influenced by plant growth regulators (PGRs). The effect of different plant growth regulators was assessed on callus induction, in vitro shoot regeneration and hairy root formation in tomato. The maximum callus induction frequency was recorded culturing hypocotyls, while in vitro shoot regeneration frequency was significantly higher when leaf discs were used as explants. The highest callus induction frequency (67.48%) was recorded in cv. Rio Grande followed by Roma (62%) and Moneymaker (58.23%) on MS basal media along with 2.0 mg/l IAA and 2.5 mg/l BAP. Similarly, the highest in vitro shoot regeneration frequency (69.6 and 65.3%) was recorded in Rio Grande and Roma on MS media fortified with 0.1 mg/l IAA, 1.0 mg/l ZEA and 2.0 mg/l BAP, while in case of Moneymaker, the highest in vitro shoot regeneration frequency (67.3%) was obtained on MS media enriched with 0.1 mg/l IAA and 3.0 mg/l BAP. The highest hairy root formation frequency (100, 91.72 and 93.74%) was achieved in cvs. Rio Grande, Moneymaker and Roma, respectively on MS media supplemented with 0.1 mg/l IAA, 2.0 mg/l ZEA and 2.0 mg/l BAP. These optimized procedures would be applicable to other genotypes of tomato for the development of cultivars tolerant to abiotic stresses developed via Agrobacterium mediated transformation system. Key words: Hypocotyls; In vitro morphogenesis; Leaf discs; Plant growth regulators, Hairy roots. INTRODUCTION In vitro morphogenesis has developed a significant importance in plant biotechnology (Vasil, 2008; Shah et al., 2013), but still there are some failures in producing new organs and tissues in certain cell types (Lima et al., 2009) because various genotypes of tomato have different morphogenic potentials (Tomsone et al., 2004; Vasil, 2008). Genetic make-up of plants is not an absolute factor for controlling their morphogenesis but plant growth regulators also have a greater influence on morphogenesis (El-Bakry, 2002; Ahmed et al., 2012; Shah et al., 2014a). The right choice of type and concentration of cytokinin markedly influences the organogenesis because they differ between varieties with respect to their uptake, transportation, metabolism and interrelate with endogenously produced cytokinins of an explant (Magyar-Tabori et al., 2010; Amoo et al., 2013). Callus, shoot and root produced in vitro depend upon the hormonal balances i.e. the ratio of auxin and cytokinin added to the media and also upon explant type (Tantikanjana et al., 2001; Uzma et al., 2012). The explants age is also crucial for success of tissue culture. The soft and young explants respond quickly to culture as compared to older one (Bhatia et al., 2004). Moreover, the hormonal requirements for callus induction and regeneration are different for different crops (Faisal et al., 2012). Thus the endogenous metabolisms of hormones are key factors for in vitro morphogenesis (Cary et al., 2001). Therefore every time they must be optimized for each experiment (Plevnes et al., 2006;). An efficient protocol for in vitro regeneration is crucial for the development of stress tolerant cultivars through genetic transformation (Godishala et al., 2011; Shah et al., 2014b). Unfortunately, the regeneration system of tomato is several times lower than those of other Solanaceae family members (Venkatesh and Park, 2012). This is the first report about hairy root formation in tomato with the application of plant growth regulators. We have developed the tissue culture protocol for local tomato genotypes culturing different explants for callus induction and in vitro shoot regeneration. Our standardized approach would be beneficial for callus induction and in vitro shoot regeneration of recalcitrant germplasms of tomato by transferring foreign genes via Agrobacterium-mediated genetic transformation. The Journal of Animal & Plant Sciences, 25(2): 2015, Page: 528-538 ISSN: 1018-7081