Arbuscular mycorrhizal fungi and micropropagation of Ranunculus asiaticus L.: a useful alliance?

The present work is aimed at providing new information about the role of arbuscular mycorrhizal fungi (AMF) in improving the acclimatization and establishment of micropropagated plants of Ranunculus asiaticus L. Micropropagated plantlets of R. asiaticus were multiplied and rooted in vitro. Ex vitro plantlets were inoculated with three different commercial inocula, based on arbuscular mycorrhizal fungi: (1) Funneliformis mosseae (GM); (2) F. mosseae, Rhizophagus intraradices and Glomus sp. (MIX); (3) F. mosseae, R. intraradices, Viscospora viscosa, plant growth promoting rhizobacteria (MF) and saprotrophic fungi. A two-step inoculation method has been carried out: mycorrhizal inoculum was added to pots filled with peat substrate at acclimatization phase and a further inoculation occurred when plants were transplanted to field conditions. Plants growth was followed all over the culture cycle till harvesting the tuberous roots. Our findings showed that ex vitro plantlets of R. asiaticus already form arbuscular mycorrhizae during the acclimatization phase. MF inoculum had the lowest root colonization levels, while the MIX and GM-inocula provided satisfactory results with high levels of root colonization. Once in the field, MIX-treated plants showed an earlier flowering, an improved flower production and somewhat better rhizome yield at the end of the culture cycle if compared to the control (untreated plants). GM-treated plants performed in a way not significantly different from the control. MF-treated plants evidenced the worst performance with a low flowering efficiency. From our results it can be argued that ex vitro R. asiaticus plantlets can be colonized by AM fungi; however, different AMF species in the inoculum can affect the performance of plants when transferred to the field.