Date of Award

Spring 5-13-2017

Semester of Degree


Document Type

Open Access Thesis

Degree Name

M.S. in Environmental and Forest Biology


Environmental and Forest Biology

Major Professor

Lee Newman

Steering Committee Member

William Powell

Steering Committee Member

Mark Bremer


Bacterial endophytes colonize total plant tissue without harming their hosts. One specific endophyte, Enterobacter sp. 638, is known to produce plant hormones which result in increased biomass (Taghavi et al., 2011). This study examined the effects of E. 638 inoculation and stress on growth of tomatoes (Solanum lycopersicum). Stressed inoculated plants produced significantly more fruit, and flowered, set fruit and ripened earlier than uninoculated plants. Stressed inoculated plants also had 30% larger root mass; however inoculation had no significant impact on unstressed plants. In addition, qPCR was used to measure the effects of inoculation on relative expression of certain genes in tomato root tissue. Inoculated plants had significantly higher transcript levels of ethylene signaling protein (EIN2), cytokinin receptor protein (CRE1) and cell wall relaxing protein (EXPA4) compared to uninoculated controls. These results may have major implications to agriculture by potentially enabling sustainable crop production under stressful conditions.