Induction of sporophytical divisions and formation of embryo structures in microspore culture of tomato (Lycopersicon esculentum Mill.)

In this study, the effect of cold treatment (4 °C for 1 to 5 days) in combination with heat shock (30 °C for 1 to 10 days) and also colchicine treatment (25 to 100 mg/l for 24 to 72 h) were assessed on induction of sporophytical divisions in isolated microspore culture in two hybrid tomato cultivars (‘Berlina’ and ‘Petoperide’). Microspore-derived structures with more than 10 nuclei were only observed in cv. ‘Berlina’ and in the cultures incubated for 1 or 2 days at 4 °C and then for 2 days at 30 °C. In addition, cold treatment for 1 or 2 days and then 2 days at 30 °C could efficiently induce formation of microspore-derived structures with 9-10 nuclei in both cultivars tested. No microspore with more than 5 nuclei was observed in the cultures treated at 30°C for 10 days. In the cv. ‘Berlina’, microspore-derived structures with 9-10 nuclei were detected when 25 mg/l colchicine was used for 48 h, while in cv. ‘Petoperide’, microspore-derived structures with more than 8 nuclei were not observed in all treatments tested. Globular embryos were only produced in two-layered culture medium when treated at 4°C for 2 and 5 days and then subjected to 30°C for 2 days. Microspore embryogenesis could be induced in tomato if appropriate duration of cold and heat treatment was selected.