Identification of Triazine-Resistant Vulpia bromoides

In Australia, triazine herbicides have routinely controlled the Vulpia species (Vulpia bromoides, Vulpia myuros, and Vulpia fasciculata; collectively referred to as silvergrass). However, a simazine-resistant silvergrass biotype, collected from Pingelly in the Western Australian grain belt in 2014, has been confirmed. Compared to the pooled mortality of three simazinesusceptible silvergrass populations (S1, S2, and S3), the simazine-resistant Pingelly population was . 594-fold resistant at the LD50 level. Dose-response screening of the simazine-selected progeny (. 800 g ai simazine ha1 ) demonstrated that the simazine resistance mechanism was heritable. Sequencing of the chloroplast psbA gene revealed the resistant population is homozygous for a serine 264 to glycine mutation, which confers a high-level triazine resistance. As expected this Ser-264-Gly mutation conferred resistance to atrazine and metribuzin, but not the phenyl-urea diuron. This is the first published report confirming field-evolved triazine resistance in a Vulpia population.

Weed Technology, online