Assessing the biostimulant effect of micro-algae and thyme essential oil during in-vitro and ex-vitro rooting of strawberry

To improve the micropropagation protocol and the regeneration rate of the strawberry (Fragria pound ananassa Dutch) Camarosa variety, the use of natural biostimulants was investigated since the application of synthetic chemicals in agriculture to ensure optimal growth is not always satisfactory. Indeed, strawberry in vitro rooting depends on the use of plant growth regulators, which may cause the development of aberrant and undesirable physiological and epigenetic disorders. For this purpose, the effects of thyme essential oil (TEO) and a mix of microalgae consortia (MA) were studied. These treatments were tested at two different concentrations during the in vitro rooting phase using nodal segments of the plant inoculated on MS medium. In vitro, root development exhibited a significant difference between treated and control plants. Later, the impact of both treatments on the growth of ex-vitro strawberry seedlings was studied during the acclimatization phase; hence, physiological, and biochemical analysis confirmed these findings. In fact, a positive effect of both treatments on the shoot and root parts of plants was observed. This was proven through an increase, compared to the control, in the root system by 74%, the number of leaves by 21,1%, and the shoot by 24,3% resulting in an acceleration of the initiation of rhizogenesis. On another hand, the physiological analysis revealed an improvement in the chlorophyll content in the treated leaves. Furthermore, with both treatments applied, there was a progressive and significant increase (p <0,05) in the activity of some enzymes such as peroxidase and in the phenol as well as hydrogen peroxide contents in the leaves revealing an induction of the antioxidant activity in the plant.(c) 2023 Published by Elsevier B.V. on behalf of SAAB.

Automated summary

This study investigated the use of natural biostimulants to improve the micropropagation and regeneration rate of strawberry plants. Thyme essential oil and a mix of microalgae consortia were found to positively affect root development and growth in vitro. The treated plants also showed increased chlorophyll content and induced antioxidant activity.