Lolium ridigum

This research reveals the complexity of the α-tubulin gene family in individuals/populations of the cross-pollinated weedy species L. rigidum, and highlights the need for better understanding of the molecular architecture of tubulin gene families for detecting resistance point mutations. Although TUA4 is a commonly expressed α-tubulin isoform containing most frequently reported resistance mutations, other mutant tubulin isoforms may also have a role in conferring dinitroaniline resistance.

Authors: Jinyi Chen, Zhizhan Chu, Heping Han, Eric Patterson, Qin Yu and Stephen Powles

This study shows that the resistance mechanism endowing pyroxasulfone resistance in this Lolium rigidum population is enhanced rates of pyroxasulfone metabolism. This enhanced rate of pyroxasulfone metabolism is associated with over-expression of two glutathione transferases. Thus, the resistance mechanism in this Lolium population of enhanced rates of pyroxasulfone metabolism suggests GST-catalysed increased rates of glutathione conjugation. More work is required for definitive evidence of specific responsible GSTs.

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.

Lolium rigidum populations in Australia and globally have demonstrated rapid and widespread evolution of resistance to acetyl coenzyme A carboxylase (ACCase)-inhibiting and acetolactate synthase (ALS)-inhibiting herbicides. Thirty-three resistant L. rigidum populations, randomly collected from crop fields in a most recent resistance survey, were analysed for non-target-site diclofop metabolism and all known target-site ACCase gene resistance-endowing mutations.

The interaction between environment and genetic traits under selection is the basis of evolution. In this study, we have investigated the genetic basis of herbicide resistance in a highly characterized initially herbicide-susceptible Lolium rigidum population recurrently selected with low (below recommended label) doses of the herbicide diclofop-methyl.