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psbA mutation (valine₂₁₉ to isoleucine) in Poa annua resistant to metribuzin and diuron

Mengistu, L.W., Mueller-Warrant, G.W., Liston, A., Barker, R.E.
Pest management science 2000 v.56 no.3 pp. 209
Poa annua, biotypes, metribuzin, diuron, herbicide resistance, photosystem II, nucleotide sequences, resistance mechanisms, mutation, biological resistance
The herbicide-binding region of the chloroplast psbA gene from a total of 20 biotypes of Poa annua L resistant and susceptible to metribuzin and diuron was selectively ampli®ed using PCR. Sequence analysis of the fragment from six herbicide-resistant biotypes of P annua exhibited a substitution from valine to isoleucine at position 219 of the D1 protein encoded by the psbA gene. This is the same mutation as reported for Chlamydomonas and Synechococcus through site-directed mutagenesis and in cell cultures of Chenopodium rubrum L. To our knowledge this is the ®rst report of a higher plant exhibiting resistance in the ®eld to photosystem II inhibitors due to a psbA mutation other than at position 264. The existence of additional biotypes of P annua resistant to diuron or metribuzin but lacking mutation in the herbicide-binding region indicates that resistance to these herbicides can also be attained by other mechanisms.