Title: Evolution in action: plants resistant to herbicides
Abstract: Modern herbicides make major contributions to
global food production by easily removing weeds and substituting for destructive
soil cultivation. However, persistent herbicide selection of huge weed numbers
across vast areas can result in the rapid evolution of herbicide resistance.
Herbicides target specific enzymes, and mutations are selected that confer
resistance-endowing amino acid substitutions, decreasing herbicide binding.
Where herbicides bind within an enzyme catalytic site very few mutations give
resistance while conserving enzyme functionality. Where herbicides bind away
from a catalytic site many resistance-endowing mutations may evolve.
Increasingly, resistance evolves due to mechanisms limiting herbicide reaching
target sites. Especially threatening are herbicide-degrading cytochrome P450
enzymes able to detoxify existing, new, and even herbicides yet to be
discovered. Global weed species are accumulating resistance mechanisms,
displaying multiple resistance across many herbicides and posing a great
challenge to herbicide sustainability in world agriculture. Fascinating genetic
issues associated with resistance evolution remain to be investigated,
especially the possibility of herbicide stress unleashing epigenetic gene
expression. Understanding resistance and building sustainable solutions to
herbicide resistance evolution are necessary and worthy challenges. [Stephen B.
Powles and Qin Yu (2010). Evolution in action: plants resistant to
herbicides. Annual Review of Plant Biology, 61(1),317-347.]