Cultural behavior of protoplasts from different organs of eggplant (solanum melongena L.), and plant regeneration

Abstract

Plants of Solanum melongena were propagated under in vitro conditions (27°C, 12h/day illumination at 62 μEm^-2s^-1, 60% humidity) by subculture of terminal and lateral cuttings on MS medium +20 gl^-1 sucrose + Morel and Wetmore vitamins at 1/8 strength and 7 gl^-1 agar. Lamina, petioles and stems of 3-week-old cuttings were used as sources of protoplasts. The best mean yield of protoplasts was obtained from the lamina with 9,030×10³ protoplasts per gram of tissue. Petioles and stems yielded respectively 3,144×10³ and 1,220.4×10³ protoplasts per gram of tissue. first division of petiole and stem protoplasts occurred within 48 h, while lamina protoplasts underwent division after 3–4 days of culture in KM8p medium +2,4-D(0.2 gl^-1) + zeatin (0.5 mgl^-1) + NAA (1 mgl^-1) and 0.35M glucose as osmoticum. The highest percentage of dividing cells was obtained from petiole material, estimated at 33.4% after 7 days, compared to 23.8% and 19.4% respectively for stem and lamina protoplasts. When BAP replaced zeatin in KM8p, the division percentage of lamina protoplasts was reduced to 10–15%. When transferred to regeneration medium, all calli derived from KM8p + zeatin formed deep-green spots identified as embryo-like structures, while only few calli from KM8p + BAP underwent shoot organogenesis without formation of green spots. Some of embryo-like structure developed into plantlets with a frequency of 1–2 plantlets per callus especially on MS medium + zeatin (4 mgl^-1) + IAA (0.2 mgl^-1). Maintaining protoplast-derived calli on MS + BAP (0.5 mgl^-1) + NAA (0.5 mgl^-1) for more than 3 weeks resulted in a decrease and loss of cell totipotency.