Novel Tubulin Mutations Conferring Resistance to Dinitroaniline Herbicides in Lolium rigidum

The paper Novel Tubulin Mutations Conferring Resistance to Dinitroaniline Herbicides in Lolium rigidum was published in Frontiers in Plant Science, 2018, Volume 9, Article 97. It involves AHRI researchers, plus first author Dr Zhizhan Chu, a China Scholarship Council scholar in AHRI from South China Agricultural University, Guangzhou and Modeller Dr Alex Nyporko in Kiev, Ukraine.

The dinitroaniline herbicide trifluralin has for many years been widely used in Australian grain cropping.  In recent years trifluralin resistant Lolium has become evident, especially in South Australia (research from Boutsalis, Fleet, Preston) and to a lesser extent in Western Australia (Mechelle Owen – AHRI resistance surveys).

This research documented target site resistance in a Lolium population resistant to trifluralin and other dinitroaniline herbicides.  Target site resistance in this particular population is endowed by changes at Arginine 243 of the alpha tubulin gene. PCR work established that amino acid substitution of Arg 243 with either Met or Lys endows 4-8 fold trifluralin resistance.

Definitive evidence that these 243 Met or Lys substitutions are responsible for resistance was obtained by transforming rice calli with tubulin gene expressing these substitutions and showing that they endowed trifluralin resistance.

Finally, due to the collaboration with modeller Alex Nyporko, comprehensive modelling showed the docking of trifluralin on the tubulin gene and how these resistance-endowing 243 Met or Lys substitutions unfavourably change trifluralin binding.

Commentary from AHRI Director Steve Powles indicates that this study clearly and comprehensively establishes that target site resistance to dinitroaniline herbicides can be endowed by mutation changing the alpha tubulin gene at amino acid 243, changing Arg to either Met or Lys.  Of course, other mutations elsewhere on the alpha tubulin gene are known to endow resistance.  Interestingly, these mutations changing amino acid 243 appear to endow a fitness cost.

Author and AHRI PhD student Jinyi Chen is conducting further research on the fitness of this mutation, as part of her PhD.