Detecting herbicide-resistant Apera spica-venti with a chlorophyll fluorescence agar test

Abstract

Reliable tests on herbicide resistance are important for resistance management. Despite well-established greenhouse bioassays, faster and in-season screening methods would aid in more efficient resistance detection. The feasibility of a chlorophyll fluorescence agar-based test on herbicide resistance in Apera spica-venti L. was investigated. Herbicide resistant and sensitive A. spica-venti seedlings were transplanted into agar containing pinoxaden and pyroxsulam herbicides. Chlorophyll fluorescence was measured and the maximum quantum efficiency of photosystem II (Fv/Fm) was determined 48 h and 72 h after the transplantation to agar, respectively. The Fv/Fm values decreased with increasing herbicide concentration. Dose-response curves and respective ED50 values (herbicide concentration leading to 50% decrease of the Fv/Fm value) were calculated. However, each experiment repetition exhibited different sensitivities of the populations for both herbicides. In certain cases, resistant populations demonstrated similar Fv/Fm values as sensitive populations. Contrary to the findings in Alopecurus myosuroides Huds., discrimination of sensitive and resistant A. spica-venti populations was not feasible. An increased importance of the assessment time due to the herbicide concentrations calibrated for fast responses was assumed in this study.