|GRIMSHAW, A - University Of Georgia|
|SCHWARTZ, B - University Of Georgia|
|MCCULLOUGH, P - University Of Georgia|
|GREY, T - University Of Georgia|
|RAYMER, P - University Of Georgia|
|KOWALEWESKI, A - University Of Georgia|
|TRENT, T - University Of Georgia|
|PARROTT, W - University Of Georgia|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2014
Publication Date: 4/23/2014
Citation: Grimshaw, A., Schwartz, B., Mccullough, P., Grey, T.L., Raymer, P., Webster, T.M., Kowaleweski, A., Trent, T., Parrott, W. 2014. Acetyl-CoA Carbuxylase herbicide tolerance in bermudagrass. Agronomy Journal. 106(3):925-930.
Interpretive Summary: Bermudagrass is a warm-season perennial grass that is used widely in the southern United States, India, Australia, Africa and South America. It is generally regarded as having exceptional tolerance to heat and drought, but poor tolerance of shade and freezing temperatures. Improved bermudagrass cultivars provide durable turf on golf courses, sports fields, recreational areas, forages and home lawns. In most intensely managed turf areas, improved varieties of bermudagrass that include sterile hybrids are preferred because of their superior aesthetics and performance throughout many years and in different situations. These sterile hybrids are clonally propagated and are transplanted as sod or sprigs when established in new turf areas. Currently there are no selective herbicides to control common bermudagrass that has contaminated a hybrid cultivar due to a lack of differential tolerance. Renovating and installing turf can be an expensive and time consuming task. A new variety which has the potential to be managed with ACCase herbicides to limit contamination by grassy weeds would benefit turf users by increasing the potential for successful establishment and extending the timeframe between replacement. This research demonstrated 93-175 has the ability to tolerate herbicide applications that significantly injured non-tolerant genotypes. While 93-175 does have greater turf quality characteristics, i.e. density, uniformity, and growth habit, than other tetraploid bermudagrasses, much of its value lies in that it is fertile and may have the ability to transfer ACCase herbicide tolerance to offspring. Currently, 93-175 is being used as a parent in crosses at the University of Georgia and its progeny will be evaluated for inheritance of herbicide tolerance. Incorporation of ACCase herbicide tolerance into sterile triploid bermudagrass hybrids in the future, assuming the trait is transmissible, would be a desired form of release for this technology. Strategies that prevent or reduce the likelihood that ACCase herbicide tolerance is transferred to weedy bermudagrasses should be pursued so that the utility of this trait is not lost for turf managers.
Technical Abstract: Contamination of newly planted bermudagrass (Cynodon spp. L.) varieties by undesirable offtype bermudagrass genotypes is an ever increasing concern for turf managers because selective control options are limited. In 2009, a sethoxydim tolerant bermudagrass genotype (93-175) was identified during herbicide screening at the University of Georgia in Tifton. The objective of this research was to assess the ACCasse herbicide tolerance of 93-175 in comparison to susceptible genotypes. Greenhouse and field trials were carried out between August 2011 and April 2013. Factors in the greenhouse experiment included ACCase herbicides (sethoxydim, clethodim, and fluazifop), application rate (0.25x, 0.5x, 1x, 2x, 4x, 6x, 8x,and non-treated), bermudagrass genotype (93-175, ‘Tifway’, and common bermudagrass), and run (1 and 2). Results from the greenhouse indicated that 93-175 generally had higher levels of tolerance to sethoxydim than Tifway and common bermudagrass. Field experiments were then conducted using the same herbicides and genotypes at two separate testing locations. Turfgrass injury ratings taken 42 DAT and during greenup the following spring supported previous findings. At the 1x rate of sethoxydim (280 g ai ha-1), 93-175 displayed 50 to 87 % less injury in comparison to the susceptible genotypes. In the spring of 2013, 93-175 plots treated with a 1x rate of sethoxydim reached 100% recovery during the same time period as non-treated controls, while common and Tifway had only recovered to 48 and 60 %, respectively. 93-175 will continued to be studied to determine transferability of herbicide tolerance to progeny and the mechanism of the observed tolerance.