Performance of Quercus suber L. at nursery stage-application of two bio-inoculants under two distinct environments

Key message Despite the fact that the technique of application of bioinoculants improved the quality of Quercus suber L. seedlings produced in nurseries, these benefits are dependent on the ecological conditions of the site and the composition of the applied inoculum, which interferes with the profile of the local fungal community. Context Quercus suber L. plays a key ecological and socio-economical role in the Iberian Peninsula. Symbiotic ectomycorrhizal fungi-ECM are crucial partners of several tree species, and assessing the efficacy of bioinoculants at nursery stage helps devising tools to increase plant resilience. Aims The aim of this study was to compare the effects of two inocula formulations of mixed ECM fungi and bacteria on the quality of seedlings produced in two forest nurseries, differing in environmental conditions and forest embedment. Methods Quercus suber L. seedlings were inoculated with a commercial product containing Pisolithus tinctorius (Pers) Coker Couch, Scleroderma sp., and six bacterial species and with a non-commercial fungal and bacterial dual inoculum (Suillus granulatus (L.) Roussel + Mesorhizobium sp.). Biometric and nutritional parameters and morphological quality indexes were determined on seedlings. The ECM community was assessed by denaturing gradient gel electrophoresis and cloning-sequencing. Results In both nurseries, the seedling quality index in inoculated was up to 2-fold higher than in non-inoculated seedlings. Plant biomass differed significantly among nurseries. The inoculum influenced the profile of the fungal community. S. granulatus and P. tinctorius persisted for 6 months in the inoculated seedlings. Conclusion The nursery ecosystem influenced plant growth. Inoculation treatments increased plant performance; however, the dual inoculum resulted in more consistent improvements of Q. suber at nursery stage, highlighting the importance of inocula selection.