Agueda Rodriguez; Michael Hope, Southern Utah University
Manzanita (Arctostaphylos), an evergreen shrub common to desert regions of the western United States, are of interest for their ecological role as an important food source for wildlife, for erosion control on dry, rocky, slopes, and, for their potential use in xeriscaping due to their drought tolerance, showy flowers, and attractiveness to birds and butterflies. Very little information is available on beneficial microbes associated with manzanita despite growing evidence that rhizospheric, endospheric, and phyllospheric microbes play important roles in promoting plant growth, strengthening resistance to plant pathogens, controlling frost injury, and in controlling plant diversity within local ecosystems. Mechanisms by which plant-associated microbes influence host fitness include plant hormone production, protection of the plant from pathogen colonization, and nutrient cycling, including nitrogen fixation and phosphate solubilization. In this study, cultivation-based techniques were used to isolate bacteria from the rhizospheres of the greenleaf manzanita (Arctostaphylos patula), to characterize the isolates for evidence of plant growth promoting activities, and to identify the isolated species using 16S rRNA gene sequencing. A total of 14 manzanita plants were sampled from three distinct populations in the Cedar City region of Southern Utah. From these samples, 47 rhizospheric bacterial isolates were identified through 16S DNA sequencing. Species common to all three locals included Clavibacter michiganensis, Caulobacter sp., Pseudomonas koreensis, Pseudomonas fluorescens, and Bacillus simplex. Several of these species have been reported to promote plant growth and to contribute to pathogen resistance in other plant species, suggesting a possibility of similar beneficial associations with Manzanita.