Hyperhydricity-induced changes among in vitro regenerants of gerbera

Abstract

Gerbera (Gerbera jamesonii Bolus) ranks amid the top five commercially preferred cut-flowers in global floriculture industry. Conventionally, gerbera is propagated by seed or by vegetative approaches. However, in vitro propagation cropped up as a better alternative with high commercial success since past two decades. Simultaneously, hyperhydricity of shoots has become a matter of serious concern during in vitro propagation. For the first time in gerbera, the present study highlights the morphometrical and physiological changes in hyperhydric shoots developed in high cytokinin-supplemented media. Four concentrations (2.5, 5, 7.5 and 10 mg L − 1) of kinetin and N6-benzylaminopurine (BAP) were tested individually in supplementation with Murashige and Skoog basal medium. It was found that occurrence of hyperhydricity was significantly influenced by the type and concentrations of cytokinins used. Nevertheless, gradually increasing hyperhydricity along with significantly poorer multiplication were observed with the increasing concentrations of BAP and kinetin compared to its lower levels. Majority of explants in the presence of high levels (> 5 mg L − 1) of kinetin or BAP became hyperhydric, losing their capability to regenerate. Hyperhydric plantlets exhibited lower chlorophyll and higher relative water content, resulting in glassy appearance of leaves and shoots with pale or yellowish green color accompanied with inward folding of the leaf blade towards the midrib. The roots of hyperhydric plantlets were thinner, shorter and fewer in number. Hyperhydricity further resulted in delayed development of plantlets as well as lower frequency and size of stomata.