Effects of hormone and fertilizers on early flower induction of Dendrobium anosmum hybrid seedlings under ex vitro condition

Abstract

Early flowering of new orchids is important to save time for selecting valuable flowers and artificial induction of flowering is a critical consideration in the orchid production industry. In this study, a new Dendrobium anosmum hybrid was generated by cross-breeding between D. anosmum ‘Chau Nhu’ and D. anosmum ‘Di Linh’. The ancestors and hybrid seedlings from in-vitro culture were trained in the net house and their growth and flowering were evaluated under ex vivo conditions with specific fertilizers and hormones. The results suggest that the hybrid plants grew better than their parents in terms of stem height, stem diameter, and leaf number. Growth hormones were applied to stimulate early flowering in matured hybrids and it was discovered that ‘Keiki pro’, a commercial hormone product, produced the best results, with a flowering rate of 66.67% after two applications. Hybrid flowers varied in width from 36.36% (3.0-6.0 cm) to 63.64 % (more than 6.0 cm) from ancestral width in medium-sized and large-sized flowers, respectively. Also, the hybrid flower colours was mostly a combination of pink/violet (75C) and purple/pink (68A), which is different from their parents. Importantly, the dorsal sepal, petal colours, and shape of hybrid flowers varied significantly among individual hybrids, between hybrids and their progenitors. Some mutations in the lips and columns of the novel hybrid flowers were also visualized. Hence, the D. anosmum hybrid seedlings successfully induced flowers after a year of culture under optimal hormones and fertilizers conditions. The results can serve as a critical reference for the early flowering of the orchid seedlings.