In nature, 92 % of all terrestrial plant species live in association with mycorrhizal fungi, the most common type being arbuscular mycorrhiza, found in ca. 72 % of plant species. This form of mycorrhiza evolved over 450 million years ago and played a crucial role in the colonization of land by plants. In a mycorrhizal relationship, the fungus increases the plant’s absorptive surface for water and mineral nutrients, thereby enhancing its resistance to stresses such as drought or nutrient deficiency. The fungus itself absorbs water and minerals and delivers them to the plant via arbuscules – tree‐like fungal structures inside root cells. In exchange, the plant supplies the fungus with organic nutrients and provides habitat. Arbuscular mycorrhizal (AM) fungi can also be found, among other taxa, in various species of the genus Allium – for example, in the rhizosphere and roots of wild garlic (Allium ursinum L.).
In this study, we investigated whether the addition of an inoculant composed of wild garlic roots and rhizosphere affects the rate of AM fungal colonization of onion (Allium cepa L.) roots, given that the two plants are closely related and belong to the same genus, Allium. We also evaluated the effect of a commercial mycorrhizal inoculant and compared both inoculation methods. Mycorrhization was assessed qualitatively (presence and abundance of arbuscules) and quantitatively (root colonization rate) by microscopy, with the aim of determining if, and to what extent, either inoculation approach influences the AM fungal colonization of onion roots.
The experiment comprised six treatments: garden soil without additives, garden soil with wild garlic rhizosphere, and garden soil with commercial inoculant – each in both autoclaved and non‐autoclaved substrates. For each sample, we calculated the frequency of mycorrhizal root fragments (F), intensity of the mycorrhizal colonization (M), intensity of the mycorrhizal colonization in colonized parts of the roots (m), arbuscle density in the root cortex (A), and arbuscle density in the root cortex with mycorrhizal colonization (a).
The results showed that onions grown without added inoculant in non-autoclaved substrate were already strongly colonized, whereas in autoclaved substrate without inoculant, colonization remained very low or close to zero. In autoclaved garden soil, both the commercial and natural inoculant increased the frequency of mycorrhizal root fragments compared to the control, although the effect did not differ between inoculant types. In non-autoclaved garden soil, the addition of commercial inoculant reduced the intensity of mycorrhizal colonization in onion roots compared to the control (autoclved garden soil without any inoculants).
The study demonstrates that less intensively managed garden soils can themselves be a good source of native AM fungi, making additional inoculation unnecessary. It also highlights the need to verify the effectiveness and consistency of commercial mycorrhizal products and raises concerns about their general use.
|
