Mycorrhizal Colonization and Community Composition in Shallow and Deep Roots of Wyoming Big Sagebrush Seedlings
Sagebrush has a root morphology characterized by a high proportion of roots near the surface (upper roots), sparse branching as the root descends, and high branching deeper in the soil (lower roots). The microbial community associated with upper and lower roots may differ due to dissimilarities in the soil microenvironment where these roots grow. Important components of the soil microbial community are arbuscular mycorrhizal fungi. These fungi form symbiotic associations with plant roots that increase plant nutrient uptake and water stress tolerance. In this study, we investigated possible differences in mycorrhizal colonization and community composition between upper and lower roots. For this purpose, Wyoming big sagebrush seedlings were transplanted into a burnt site in early spring of 2012. Three months after transplanting, sagebrush roots were collected from the upper 20 cm of soil and from a depth below 60 cm. We then analyzed mycorrhizal colonization and DNA was extracted from the roots and used to characterize the mycorrhizal community by molecular methods. Both total and arbuscular colonization were significantly greater in the lower than the upper roots. The total percent colonization was 13 (±3) and 41 (±5) % for upper and lower roots, respectively. Similarly, the percent arbuscules was 0.7 (±0.2) and 5.7 (±2.0) % for upper and lower roots, respectively. Presently, we are analyzing and comparing mycorrhizal DNA sequences to investigate possible differences in mycorrhizal composition between the upper and lower roots.