The Impact of Forest Fungi on Promoting Growth and Development of <i>Brassica napus</i> L.

Inoculation of plants with fungi has been shown to increase yields by improving germination, seedling vigor, plant growth, root morphogenesis, photosynthesis, and flowering through direct or indirect mechanisms. These mechanisms include solubilization and mineralization of nutrients, facilitating their uptake by plants, regulation of hormone balance, production of volatile organic compounds and microbial enzymes, suppression of plant pathogens, and mitigation of abiotic stresses. In the presented experiments, the effect of selected forest soil fungi on the growth and development of <i>Brassica napus</i> L. seedlings was investigated. Inoculation was carried out in vivo and in pot experiments with ectomycorrhizal fungi typical for forest soils: <i>Collybia tuberosa</i>, <i>Clitocybe</i> sp., <i>Laccaria laccata</i>, <i>Hebeloma mesophaeum</i>, and <i>Cyathus</i><i>olla</i>. It was shown that all analyzed fungi produced IAA. In the in vitro experiment, <i>B. napus</i> inoculated with <i>L. laccata</i> showed stimulated root growth and greater number of leaves compared to control plants. A similar stimulatory effect on lateral root formation was observed in cuttings grown in pots in the presence of the <i>C. olla</i> fungus. In the pot experiment, the seedlings inoculated with the <i>L. laccata</i> fungus also showed increased growth of shoots and biomass. The effect of inoculation with the tested fungal strains, especially <i>C. olla</i>, on the growth and development of oilseed rape was probably indirect, as it also contributed to an increase in the number of microorganisms, especially soil bacteria. The expression of the metallothioneins in <i>B. napus</i> (<i>BnMT1-BnMT3</i>) varied depending on the fungal species. The presence of <i>C. olla</i> significantly increased <i>BnMT2</i> expression in oilseed rape. It was found that <i>BnMT1</i> expression increased and <i>BnMT3</i> transcripts decreased in plants growing in the presence of <i>L. laccata</i>. This indicates the involvement of <i>BnMT</i> in the adaptation of oilseed rape to growth in fungi presence.