High frequency embryogenesis in immature zygotic embryos of sunflower

In the present investigation, nutritional requirements for induction of a high frequency of well formed somatic embryos (SEs) from zygotic embryos (ZEs) of sunflower were assessed. Variables like genotype, embryo size (0.5-10 mm), sucrose concentration (30-240 g l(-1)), carbohydrate source (sucrose, glucose, maltose), agar strength (0.2-1.0%), basal media (MS, Gamborg, Nitsch, White), photoperiod (light/dark) and temperature (20-36 degreesC) were tested. All these variables except photoperiod had significant effect on the frequency of embryogenesis. Highest frequency of embryogenesis was facilitated by Gamborg basal salt media, 120-210 g l(-1) sucrose, 0.8-1.0% agar, smaller sized embryos (0.5-2 mm) and incubation temperature of 28-32 degreesC. In addition to these, growth regulator combinations (2,4-D, 2,4-D+kinetin, BA+NAA) in varying concentrations were tried. Media supplemented with 2,4-D promoted direct embryogenesis, BA+NAA facilitated formation of single/multiple shoots while there was no response on 2,4-D+kinetin supplemented media. Zygotic embryos with well differentiated embryos were transferred to growth regulator free half strength MS medium for whole plantlet development.