Publication Date

5-2015

Date of Final Oral Examination (Defense)

3-4-2015

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Biology

Department

Biology

Major Advisor

Marcelo D. Serpe, Ph.D.

Advisor

Stephen J. Novak, Ph.D.

Advisor

Merlin M. White, Ph.D.

Abstract

Inoculation of seedlings with arbuscular mycorrhizal fungi (AMF) is a common practice aimed at improving seedling establishment. The success of this practice largely depends on the ability of the inoculum to multiply and colonize the growing root system after transplanting. These events were investigated in Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush) seedlings inoculated with native AMF. Seedlings were first grown in a greenhouse in sterilized soil (non-inoculated seedlings) or soil containing a mixture of native mycorrhizae (inoculated seedlings). Three-month old seedlings were transplanted to 24 L pots containing soil from a sagebrush habitat (mesocosm experiments) or to a recently burned sagebrush habitat (field experiments). The mesocosm experiments were started in the spring and fall of 2011 and seedlings were grown under natural climatic conditions. Field experiments, conducted within the Morley Nelson Snake River Birds of Prey National Conservation Area, were initiated in the spring and fall of 2012. At the time of transplanting the percent root colonization was negligible for non-inoculated seedlings and ranged from 24 to 81% for the inoculated seedlings, depending on the experiment. In most experiments, 5 or 8 months after transplanting colonization was about twofold higher in inoculated than non-inoculated seedlings. During the mesocosm experiments, inoculation increased survival during the summer by 25%. In the field experiments, increases in AMF colonization were linked to increases in survival during both cold and dry periods and one year after transplanting survival of inoculated seedlings was 27% higher than that of non-inoculated ones. To characterize the effect of inoculation on the AMF community, DNA was extracted from the roots and amplified with AMF specific primers. The AMF taxa were characterized based on sequences from the LSU-D2 rDNA region. A total of 6 phylotypes were identified, two within the Claroideoglomeraceae and four within the Glomeraceae. In addition, sequences were grouped into operational taxonomic units (OTUs) with sequence similarities greater than 94%. This resulted in the identification of 29 OTUs. Ordination analyses, using non-parametric multidimensional scaling, indicated that inoculation did not alter the structure of the AMF community. Similarly, no differences in OTU composition were detected between seedlings harvested in different seasons. Individual seedlings, regardless of inoculation treatment, were simultaneously colonized by AMF belonging to 3 to 6 OTUs. The lack of significant differences in AMF communities among inoculation treatments and seasons appeared to have been related to the predominance of certain OTUs. In all experiments and treatments, four OTUs were dominant. Overall, the results indicate that the inoculum derived from native AMF contributed to the colonization of roots that developed after transplanting, resulting in higher levels of colonization than those naturally occurring in the soil without altering the AMF community. Furthermore, increases in root colonization were associated with increases in Wyoming big sagebrush seedling survival.

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