Effect of three strains of Agrobacterium rhizogenes and explant type on genetic transformation of Stevia rebaudiana

Abstract

Stevia rebaudiana Bertoni is a plant that accumulates steviol glycosides (SGs) which have a sweetening power over 300 times greater in the pure compounds than sucrose. In addition, the SGs do not provide any calories. A promising strategy to improve the SGs production is the establishment of hairy root cultures via agrotransformation. The effect of three Agrobacterium rhizogenes strains LB9402, K599 and AR4 on the induction of hairy roots in Stevia rebaudiana was evaluated. The transformation procedure was mediated by A. rhizogenes in two types of plant material: hypocotyl explants and whole seedlings. The putative hairy roots started emerging one week after infection. These roots were separated from the explants and were cultivated independently in semisolid MS culture medium for their propagation. The LB9402 strain showed the greatest virulence towards S. rebaudiana, due to the large induction of putative hairy roots after 7 and 15 days in comparison with the other strains.