Julia Hull, Weber State University
Life Sciences
Endophytes are fungi that live within aerial portions of plants for most or all of their life cycle without causing visible signs of disease. Gall forming aphids, Pemphigus betae, are highly competitive over gall site selection (Moran 1993), forming galls on the leaves of narrowleaf cottonwood and their hybrids. The favored gall location overlaps with areas of highest endophyte probability. I hypothesized that a negative correlation would exist between endophyte infection and aphid galling on leaves of backcross hybrid cottonwood trees.
I tested my hypothesis by obtaining samples of six backcross hybrid cottonwood trees along the Weber River in Weber County, Utah from 10 July to 17 July 2013. I took leaf samples of galled and ungalled leaves and the corresponding twigs from the current year and the previous year. Samples were surface sterilized using 70% ethanol and 50% bleach, aseptically plated onto potato dextrose agar, and were allowed four weeks to incubate at room temperature. Samples were scored every other day for endophytes. At the end of four weeks, data was collected and statistically analyzed was performed via Microsoft Excel t-test and a Chi-squared test.
My hypothesis was rejected. I found a significantly more endophytes associated with galled leaves than in leaves without galls. Therefore, either the aphids are attracted to the areas with high endophytes infections or aphids themselves are introducing endophytes into the leaves.