University of Illinois Study Opens Black Box of Herbicide Resistance

Agricultural weeds resist herbicides in one of two ways. In target-site resistance, a tiny mutation in the plant's genetic code means 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 genes that 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 genome that 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.

For more details, read the news article in ACES News.