In vitro completion of sexual life cycle—Production of next sporophytic generation through in vitro flowering and fruiting in Solanum americanum and Solanum villosum

Abstract

An effective method for inducing high-frequency in vitro flowering and fruiting in two important medicinal species of Solanum (S. americanum and S. villosum) was standardized. In vitro multiplied shoots were cultured on MS media supplemented with 6-benzylaminopurine (BAP) alone or in combination with silver thiosulphate (STS). Synergism between STS and BAP improved flower induction. Flowering frequency enriched significantly when the duration between two sub-cultures was prolonged and strength of the MS medium increased 1.5 fold. Highest response, with total 36.7 ± 0.42 (S. americanum) and 33.2 ± 0.34 (S. villosum) flowers per plant were induced within 90 days of culture in the medium containing 0.35 mg L−1 BAP and 40 μM STS. Maximum of 19 flowers bloomed together at a time in a single plant grown in a 250 ml conical flask. The increased concentration of sucrose (5.0%) in the medium and in vitro hand-pollination enhanced frequency of fruit setting. All flowers and fruits were normal in size and color as compared to in vivo plants. Along with maturation, the green fruits were turn to blackish-purple (S. americanum) or reddish-orange (S. villosum) containing 11 ± 0.52 or 18 ± 0.67 seeds per fruit, respectively. On an average, 94 ± 2.8 and 98 ± 3.1 days were required, respectively, for the completion of sexual lifecycle from shoot implantation up to germination of in vitro derived seeds produced via in vitro flowering and fruit ripening. The germination frequencies of in vitro produced seeds were 86.4 ± 2.1% (S. americanum) to 94.5 ± 2.5% (S. villosum). The present protocol has standardized a group of factors that regulates in vitro flowering, fruiting, and seed setting. This in vitro method offers a repeatable system for studying the physiological mechanism of flowering and fruiting in controlled environment and can assist improvement of other related Solanaceous crops through fast-track in vitro cross-breeding programs throughout the year without depending on season.