Effect of a non-mycorrhizal endophyte isolated from Mentha piperita on in vitro culture of Ocimum basilicum cuttings

Abstract Fungi form different types of long-term associations with plants. Fungal endophytes, which live within host tissues, may confer stress tolerance to the associated plants, increasing plant fitness and biomass. In vitro micropropagation and large scale production of aromatic and medicinal plants may benefit from endophyte inoculation. Beside increasing plant growth, fungal endophytes may allow a reduction of the amount of plant growth regulators in culture media, can be employed to increase the survival rates of micropropagated plants during acclimatization in soil and could be useful to alleviate the transplantation shock. Previous experiments have shown that a plant growth promoter-hyaline sterile fungus (PGP-HSF) isolated from Mentha piperita L. increased plant growth and influenced the essential oil composition in the same species. In this research, we analysed the SSU rDNA regions of PGP-HSF to determine/confirm its systematic position, which is still uncertain, and investigated the effect of the fungus on in vitro sweet basil (Ocimum basilicum L.) cuttings cultured on a diluted MS medium. The Bayesian and maximum likelihood analysis of SSU rDNA regions confirmed the previously recognized collocation of PGP-HSF in the Sordariomycetes, positioning it as a sister taxon of clade Ophiostomataceae. After 35 days of co-culture of O. basilicum with the fungus, most of the growth parameters were significantly increased. Plant fresh and dry weight, number of leaves, as well as the total leaf area plant-1 showed an increase greater or equal to 100% in inoculated plants if compared to non-inoculated control plants. The root-to-shoot biomass ratio also increased. These results encourage us to deepen the effects of this endophyte on basil, by studying its influence on the production of essential oils and the post-in vitro culture.