Abstract:The regeneration capacity of six types of explants (segments from hypocotyl, cotyledons, epicotyl, leaf, internodes and petiole) was compared in 13 cultivars of tomato (Lycopersicon esculentum Mill). Explants were cultured on a regeneration medium containing 1 mg/l zeatin and 0.1 mg/l indole-3-acetic acid. The number of shoot primordia and shoots with 1 or more fully developed leaves was evaluated after 6 weeks. The regeneration capacity was significantly influenced by cultivars and explant types. The total number of shoot primordia produced in all types of explants was highest in the cultivars Hana and Premium and lowest in UC 82 and Money Marker. Cv. Hana also produced the highest number of shoots. The most responsive explants in most cultivars were hypocotyls and epicotyls with up to 100% regeneration and mean production of 6.3 and 6.5 shoot primordia per explant, respectively.

ABSTRACT:We studied the effect of different plant growth regulators on in vitro regeneration and plant growth of three cultivars of tomato (Lycopersicon esculentum Mill.) from explants derived from hypocotyls and cotyledons of aseptically grown seedlings. The regeneration capacity was significantly influenced by cultivar and explant type. The highest number of shoots regenerated in both types of explants was recorded on MS medium supplemented with 1.0 mg/dm 3 zeatin and 0.1 mg/dm 3 IAA. The cultivar UC 82 showed the best regeneration capacity on all types of used media. The most responsive explants were hypocotyls with 90-92% regeneration in dependence on the used cultivars and mean production from 0.18 to 0.38 shoots per explant. 119of MURASHIGE and SKOOG (1962) (hereinafter abbreviated as MS), 100 mg/dm 3 myo-inositol, 2 mg/dm 3 thiamine.HCl, 0.5 mg/dm 3 pyridoxine. HCl, 0.5 mg/dm 3 nicotinic acid, 1% (w/v) sucrose and 0.7% (w/v) agar. The cultures were initially kept in the dark at 27 ± 1°C for two days and then maintained under a 16 h photoperiod at 50 µmol m 2 s, with day/night temperature of 25°C/20°C. Hypocotyl and cotyledon segments were cut from the seedlings grown in vitro. The hypocotyls were cut into three segments. Each cotyledon was transversally cut into two segments. Hypocotyls were transversally cut into 4-7 mm segments and leaf-blades into pieces of 30-40 mm 2 . The hypocotyl explants were placed horizontally on the medium surface and cotyledon explants with the adaxial surface in contact with the medium. Regeneration was induced on MS medium supplemented with different concentrations of cytokinins (ZEA, BAP, TDZ) and auxin (IAA) (Table 1). After 3 weeks cultured explants were transferred on: 1) MS without plant growth regulators (PGRs), 2) MS medium contains half concentration of PGRs and 3) MS medium with full concentration of PGRs (Fig. 1). The media were adjusted to pH 5.8 prior to autoclaving. Glass containers with 25 cm 3 of medium were used.Six weeks later the regeneration capacity of explants was assessed. The following parameters were evaluated: the frequency of regeneration (percent of regenerating explants) and the number of shoots per explant. Data on regeneration frequency (%) were transformed by arcsin√x prior to statistical analysis. The experiment was repeated twice using 30 explants per variant. Significance of difference between the results was estimated by analysis of variance (ANOVA). Variation among means was analysed using LSD (P ≤ 0.05) procedure. RESULTSThe effect of different tomato cultivars and different PGRs concentrations on shoot regeneration from aseptically grown hypocotyls and cotyledons showed significant variation in both the genotype and PGRs. A large variability in the number of shoots was observed between cultivars and between the different PGRs concentrations (Table 2). Cultivar mean comparisons (least significant difference, LSD, P ≤ 0.05) showed only two classes differing in the induction potential. The cultivar which produced the most shoots on hypocot...

In vitro regeneration of cultivated tomato (Lycopersicon esculentum Mill.) has been a subject of research because of the commercial value of the crop and its amenability for further improvement via genetic manipulation (EVANS 1989). The most successful procedure is regeneration through adventitious organogenesis ( VAN ROEKEL et al. 1993;FRARY, EARLE 1996;PERES et al. 2001). The in vitro morphogenetic responses of cultured plants are influenced by several different components of the culture media and it is important to evaluate their effect on plant regeneration. The purpose of our study was to evaluate the influence of carbon source on plant regeneration in tomato.Three cultivars of tomato (Lycopersicon esculentum Mill.), Premium, Hana and UC 82, were used. The seeds were surface-sterilised by immersion into a 4% solution of sodium hypochlorite for 15 min and rinsed four times with sterile distilled water. The seeds were then germinated in glass containers with 25 cm 3 of a half-strength medium of MURASHIGE and SKOOG (1962) (abbreviated hereinafter as "MS"), 100 mg/m 3 myo-inositol, 2 mg/dm 3 thiamine.HCl, 0.5 mg/dm 3 pyridoxine.HCl, 0.5 mg/dm 3 nicotinic acid, 1% sucrose and 0.7% agar. The cultures were initially kept in the dark at 27 ± 1°C for two days and then maintained under a 16h photoperiod at 50 µmol/m 2 s, with day/night temperature of 25°C/ 20°C. Hypocotyl and cotyledon segments were cut from the seedlings grown in vitro. The hypocotyls were cut into three segments. Each cotyledon was transversally cut into two segments. Hypocotyls were transversally cut into 4-7mm segments and leaf-blades into pieces of 30-40 mm 2 . The hypocotyl explants were placed horizontally on the medium surface and cotyledon explants with the adaxial surface in contact with the medium. The effect of different concentrations of sucrose, glucose and maltose (1.0, 2.0 and 3.0%) that were added to the MS basal medium supplemented with 1 mg/dm 3 zeatin (ZEA) and 0.1 mg/dm 3 indole-3-acetic acid (IAA) (ICHIMURA, ODA 1995) on regeneration capacity of explants was studied. The media were adjusted to pH 5.8 prior to autoclaving. Glass containers with 25 cm 3 of medium were used. The regeneration capacity of explants was assessed 6 weeks later. The following parameters were evaluated: frequency of regeneration (percents of regenerating explants) and the number of shoots per explant. Significance of differences between the results was estimated by analysis of variance (Statgraphics Version 5.0). Variation among means was analysed using LSD (P ≤ 0.05) procedure according to the method described by SNEDECOR and COCHRAN (1956). The effect of different tomato cultivars and different sugar types (sucrose, glucose and maltose) and concentrations (1.0, 2.0 and 3.0%) on shoot regeneration from aseptically grown hypocotyl and cotyledon explants were studied. Among sugar types, sucrose at a concentration of 3.0% induced the highest number of shoots from both types of explants. In hypocotyl explants, cv. Premium showed the best regeneration capacit...