Agricultural weeds resist herbicidesin one of two ways. In target-site
resistance, a tiny mutation in the plant's genetic codemeans the
chemical no longer fits in the protein it is designed to attack. In
non-target-site resistance, the plant deploys a whole slew of enzymes
that detoxify the chemical before it can cause harm.

Target-site resistance is easy for scientists as they know the target
protein and can look directly at the genetic code to figure out the
mutation responsible. However, this is not the case for non-target-site
resistance. Researchers can sometimes tell what class of enzymes
detoxifies the chemical but know nothing about the genesthat code for
those enzymes. In other words, non-target-site resistance is a black
box. A University of Illinois study led by Professor Pat Tranel is the
first to open that box, identifying gene regions responsible for
non-target-site herbicide resistance in waterhemp.

According to Tranel, they used a genetic mapping approach with the
reference genome for waterhemp, a species that can cause yield losses or
more than 70 percent in corn and is resistant to seven herbicide modes
of action. His team was able to narrow it down to two regions of the
genome, or about 60 genes. Genetic mapping helped the team identify the
two regions of the waterhemp genomethat seemed to be associated with
resistance. They were also able to identify which plants had each of the
two regions, and which had both, allowing them to rank the importance of
the gene regions.

Herbicide resistance no longer a black box for scientists | College of
Agricultural, Consumer & Environmental Sciences :: University of
Illinois
[aces.illinois.edu]