Expression of cry1Fa in bahiagrass enhances resistance to fall armyworm

Bahiagrass (Paspalum notatum var. saurae) is the predominant forage grass in Florida and in other subtropical regions. To improve pest resistance against fall armyworm [Spodoptera frugiperda (J. E. Smith)], an optimized cry1Fa gene encoding a 8-endotoxin from Bacillus thuringiensis was synthesized, subcloned under the transcriptional control of the constitutive ubi1 promoter, and introduced into the bahiagrass cultivar Tifton 9 by particle bombardment. Three transgenic bahiagrass lines were generated using minimal transgene expression cassettes without vector backbone. Southern blot analyses showed independent cry1Fa transgene integration patterns for the three lines. Transcripts of cry1Fa were detected in all three transgenic lines by reverse transcriptase polymerase chain reaction. Cry1Fa protein was detected in two lines by immuno-chromatography and quantitative Cry1Fa enzyme linked immunosorbent assay (ELISA). The Cry1Fa ELISA also indicated stable cry1Fa transgene expression in vegetative progeny plants of both lines. Cry1Fa expression levels correlated well to resistance levels determined by insect bioassays. An average mortality rate of 83% was observed when neonate larvae of fall armyworm were fed with transgenic leaves of the highest cry1Fa expressing line. These results indicate that minimal expression cassette technology supports stable and high level expression of cry1Fa in bahiagrass which can control fall armyworm, a devastating pest of forage grasses.