Optimisation of the micropropagation protocol of cultivated strawberry (Fragaria × ananassa Duch.)

Currently, the production of all certified strawberry plants in France is permitted through a unique in vitro propagation protocol for all the cultivars available regardless of the physiological characteristic of each the cultivar. The aim of the study is to improve the current protocol of in vitro culture of strawberry and therefore the quality of the plants produced as well as the economic profitability of the lab. In vitro production can be split in three stages: first the introduction by meristem excision, the multiplication of the micropropagated plants (maximum ten subcultures) and finally the rooting of the plants. In this study, only the in vitro multiplication stage has been studied by using a range of mineral (macro-elements) and hormonal concentrations (auxins and cytokinins) compared with the standard media currently used by a French laboratory. The plants were multiplied 5 to 6 times on those different media and then the strawberry shoots were transferred to a rooting media end before being acclimatized. The different batch of plants were then evaluated in field trials for the production of runners. None of the modified hormonal media positively affected the multiplication rate in the laboratory or the production of runners in the field. However, a global analysis of the different culture media with modifications of the mineral bases made it possible to highlight that the ratio of two crucial mineral elements (the NH₄⁺ and the PO₄^3- ions) within the medium is the more significant factor to the in vitro plant response, bringing significant improvements of the in vitro behaviour of the plants. Concerning the runner production capacity of the plants, no difference is noted between the culture media.