Abstract
Key messageDespite the fact that the technique of application of bioinoculants improved the quality ofQuercus suberL. 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.ContextQuercus 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.AimsThe 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.MethodsQuercus 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.ResultsIn 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.ConclusionThe 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.
Highlights
Quercus suber L. is the mainstay of multiple-use agroforestry systems with great socio-economic and environmental value in the western Mediterranean region
The dual inoculum SgB excelled among inoculation treatments in Buçaco, showing higher average values for almost all growth parameters, namely, shoot dry mass, root dry mass, and stem diameter, with an increase of 1.29, 1.35, and 1.16-fold compared to the Mix, and a 1.52, 1.58, and 1.26-fold compared to the Control (P < 0.05)
In Amarante, the Mix treatment presented significantly higher values than the SgB and Control, but in Buçaco, SgB led to higher average values that significantly differed from non-inoculated and from seedlings inoculated with Mix
Summary
Quercus suber L. is the mainstay of multiple-use agroforestry systems with great socio-economic and environmental value in the western Mediterranean region For this reason, the mortality events that have been affecting this species since the beginning of the XX century, with an increase during the 1980s (CamiloAlves et al 2013), are a strong reason for concern. Ectomycorrhizal (ECM) fungi form symbiotic associations with the majority of forest trees and are crucial for their nutrition and water acquisition (Moeller et al 2014) They are strong competitors against soil-borne root parasites, providing both mechanical (Frey-Klett et al 2005) and biochemical (Cairney and Chambers 2013) protection against pathogens (Perrin and Garbaye 1983). The choice of fungal inoculants seems to be a crucial factor since not all are beneficial to plant development (Sousa et al 2012) or persist in the root system after field transplantation (Franco et al 2014)
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