Geographical and plant genotype effects on the formation of arbuscular mycorrhiza in Avena sativa and Avena nuda at different soil depths

We have examined the influence of host plant genotype and geographical characters on the vertical distribution pattern of arbuscular mycorrhiza associated with Avena. The degree of colonization of oat roots at different soil depths (0–10, 10–20, 20–30, 30–40, 40–50 cm) was compared among three habitats from lower to higher altitude and six different cultivars in one specific habitat. Altitude had no impact on the percentage of root length colonized by mycorrhiza. However, oats growing at the higher altitudes formed more abundant arbuscules and vesicles within their roots. Plant genotype showed a significant influence on the percentage of root length colonized and abundance of arbuscules and vesicles, and there was much greater colonization of naked oat than of husk oat (common oat). The vertical distribution pattern of mycorrhizal root length was similar in terms of geographical and genotypic aspects, with the most extensive root colonization occurring in the topsoil and decreasing with increasing soil depth. However, the percentage of root length colonized by arbuscular mycorrhizal fungi (AMF) remained at about 20% colonization at a depth of 40–50 cm. Intraradical structures also showed a decreasing trend with increasing soil depth. The results suggest that an AMF “gene bank” may persist in the subsoil, and this may facilitate the ecological restoration of degraded agricultural areas.