Poa Annua Population Dynamics in Response to Herbicides and Plant Growth Regulators.

Abstract

Annual bluegrass (ABG) is an invasive turfgrass species. Herbicides and plant growth regulators (PGR's) are often used for control, providing limited or inconsistent results. Identifying shifts in ABG populations in response to these treatments would be beneficial for understanding inconsistent control. Our objective was to determine 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 studies where seven different season-long ABG control treatments consisting of plant growth regulators or herbicides were applied. The herbicide trials were conducted at three different locations (West Lafayette, Indiana; East Lansing, Michigan; Lincoln, Nebraska). In the present study, markers were identified for each site and 649, 745, and 762 were produced for East Lansing, West Lafayette and Lincoln samples respectfully. Population structure analysis software (Structure v. 2.3.4) found that collections in West Lafayette consisted of seven distinct ABG populations, six in Lincoln, and five in East Lansing. Analysis of molecular variance, unweighted pair group method with arithmetic mean, and principal coordinate analysis also support these findings. Results show that PGR's in East Lansing and West Lafayette providing the best control, paclobutrazol and flurprimidol, did not effect the populations in East Lansing, but paclobutrazol did effect populations in West Lafayette. Bispyribac-sodium (bispyribac) at .14 kg ha^-1 offered the best control in Lincoln and did effect the populations. Additionally, bispyribac treatments at all locations effected the populations either at .07 kg ha^-1 or both .07 kg ha^-1 and .14 kg ha^-1. Furthermore, trinexapac-ethyl effected populations at all three locations, but did not provide effective control. This study provides a genetic basis in understanding how environment and herbicides/PGR's impact ABG populations. Results from this study will help explain inconsistencies in chemical controls, give us a better understanding into why chemical control strategies fail, and lead to a reduction in inputs and costs for controlling ABG.