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Genetic variation in native and invasive broomsedge grass populations

Faculty Mentor: Janet Morrison

Students: Brian Giacopelli & Michael Readinger

Andropogon virginicus is an important grass in old field succession that is native to the eastern regions of the United States and has also been introduced in California and Hawaii. In Hawaii it is considered invasive. In about half of the Eastern populations, A. virginicus is infected with the smut fungus Sporisorium ellisii, which is not seen in the California and Hawaii populations. We use A. virginicus to provide important insight into invasion ecology and plant pathogen interactions, by assessing its genetic diversity within and between these populations. Our research uses an analysis of ISSR molecular markers to generate DNA fingerprints for individual A. virginicus, which we will then use in the analysis.  Over the course of MUSE, we extracted the DNA of 20 individuals from 16 populations (4 from Hawaii, 4 from California, 4 from east coast states infected with S. ellisii, and uninfected 4 eastern populations).  We then began to generate the DNA fingerprints and did prelminary statistical analysis. So far, our data indicate that the non-native populations (from Hawaii and California) are less genetically diverse than their native counterparts from the eastern states, suggesting that introduction of this grass into a new territory causes a genetic bottleneck. Additionally, the populations infected with S. ellisii appear less genetically diverse than the uninfected populations, which supports our hypothesis that disease epidemics in nature should be expected where the host organism (here, the grass) is more genetically uniform. This would allow a pathogen to more easily evolve to overcome a commonly shared host defense.