Lignosulfonate promotes the interaction between Scots pine and an ectomycorrhizal fungus Pisolithus tinctorius in vitro

Lignosulfonate (LS) is a lignin-based polymer obtained as a by-product from paper industry, which may have potential as an amendment with macronutrients. We studied effects of LS on the interaction between Scots pine (Pinus sylvestris L.) seedlings and hypocotyl cuttings and the ectomycorrhizal (ECM) fungus Pisolithus tinctorius (Pers.) Coker and Couch. The experiments were performed in vitro on the MMN agar medium containing Fe-LS chelate at the concentrations of 0, 5, 10 and 25 mg/L. Inoculation with P. tinctorius increased root growth of the seedlings. Fe-LS enhanced P. tinctorius induced formation of lateral roots and had a dose-dependent positive effect on the establishment of mycorrhizas on the seedlings. The growth of the fungal mycelium was improved by Fe-LS, which might cause faster and more intensive contact with the roots and, thus, better root growth and mycorrhiza formation. P. tinctorius enhanced also adventitious root formation and subsequent root growth of the hypocotyl cuttings but without any synergistic effect with Fe-LS. Our study with P. tinctorius and Scots pine in vitro indicates that a low-cost by-product Fe-LS, obtained from paper industry, may be a potential tool to improve the efficiency of fungal inoculations, thus, facilitating the early interaction between an ECM fungus and host seedling.