Apomictic Bahiagrass Expressing the bar Gene Is Highly Resistant to Glufosinate under Field Conditions

Abstract

Bahiagrass (Paspalum notatum Flugge) is one of the most important low‐input turf and forage grasses in the southeastern USA and in other subtropical regions. Its open growth habit, however, facilitates weed encroachment and its low tolerance to commercially available herbicides complicates weed management. Genetic transformation protocols were recently developed for bahiagrass that allow now, among other approaches, the introduction of herbicide resistance genes. Integration of the bar gene expression cassette into the genomic DNA of the apomictic bahiagrass cultivar Argentine was confirmed by Southern blot analysis. Stable expression of the bar gene was detected by an immunochromatographic assay in primary transgenic lines and the seed‐derived progeny plants. Several independent transgenic lines showed no growth inhibition, chlorosis, or necrosis following a spray application of 1.0% glufosinate ammonium [2‐amino‐4‐(hydroxymethylphosphinyl)butanoic acid] under greenhouse conditions. The selected transgenic plants did not differ morphologically from wild‐type plants and produced viable seeds in the greenhouse and field. All weeds that coestablished during the field experiment, as well as wild‐type bahiagrass, displayed full leaf necrosis after application of 0.3% glufosinate ammonium. Transgenic bahiagrass plants were resistant to a field application of 0.6% glufosinate ammonium, which is twice the recommended rate for weed control, without any symptoms of phytotoxicity.