Date of this Version
Brown, J.K. 2013. Changes in Poa annua Populations in Response to Herbicides and Plant Growth Regulators (MS thesis). University of Nebraska, Lincoln, Nebraska.
Poa annua (annual bluegrass; ABG) is an invasive weedy species in turfgrass. Herbicides and plant growth regulators (PGRs) are often used for ABG control, providing limited or inconsistent results. Identifying shifts in ABG populations in response to these treatments would be beneficial for understanding inconsistent control. Our research employed amplified fragment length polymorphic (AFLP) markers with the objective to determine if there are changes in genetic structure of ABG populations after multiple-year season-long control programs in three states. Annual bluegrass was sampled after the second or third year of seven different season-long ABG treatments consisting of herbicide or PGR applications. The trials were conducted at three different locations (East Lansing, Michigan; West Lafayette, Indiana; Lincoln, Nebraska). In the ABG samples, AFLP markers were identified for each site and 649, 745, and 762 were produced for Michigan, Indiana and Nebraska, respectively. Population analysis was conducted in Structure and identified five distinct ABG populations in Michigan, seven in Indiana, and six in Nebraska. Season-long treatments of trinexapac-ethyl or bispyribac-sodium (bispyribac) at a low rate effected genetic structure of populations at all locations. However, ABG populations that were affected by an individual herbicide or PGR did not respond consistently among locations. Bispyribac treatments increased ABG population variability in Michigan, but decreased variability in Indiana and Nebraska. Trinexapac-ethyl treatments decreased ABG population variability in Michigan and Indiana, but increased variability in Nebraska. This study provides a genetic basis in understanding how herbicides or PGRs impact ABG populations over the long term and our results may help explain inconsistencies in chemical control of ABG.
Advisors: Keenan Amundsen and Zac Reicher