Investigating Herbicide Resistance and Evolutionary History Of The Highly Adaptable Turfgrass Weed Annual Bluegrass (Poa annua)

Annual bluegrass (Poa annua) is a low-growing grass species common in turfgrass throughout the world. Annual bluegrass is adapted to diverse climates and adapts rapidly to herbicide management practices. Annual bluegrass is an allotetraploid with Poa infirma and Poa supina as its diploid progenitors and it is suspected that polyploidy aids its adaptability. Annual bluegrass management with herbicides has become more problematic due to resistance development to almost all modes of action used. Two modes of action in particular, acetolactate synthase (ALS) and photosystem II (PSII) inhibitors, are commonly used for annual bluegrass control in warm-season turfgrass. These modes of action are comprised of diverse chemical families that can be variable with respect to response to specific resistance mechanism. Our research has identified Trp₅₇₄ to Leu as a mechanism of resistance to ALS-inhibitors and that the mutation leading to this amino acid substitution is contained within the Poa infirma genome in annual bluegrass. Further, we have identified the Ser₂₆₄ to Gly substitution as a mechanism of resistance to PSII inhibitors and the mutation arising from the maternal chloroplast genome of Poa infirma. As a way of preparing for future resistance development, the annual bluegrass leaf transcriptome was sequenced and known genes of target site resistance were assembled. Of particular interest are protoporphyrinogen IX oxidase and cellulose synthase that are inhibited by flumioxazin and indaziflam, respectively.