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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Production Systems Research » Research » Publications at this Location » Publication #322200
Title: Transfer and expression of ALS inhibitor resistance from Amaranthus palmeri to an A. spinosus X A. palmeri hybrid.

Author
item Molin, William
item Nandula, Vijay
item Wright, Alice
item BOND, JASON - Delta Research & Extension Center

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2015
Publication Date: 6/1/2016
Citation: Molin, W.T., Nandula, V.K., Wright, A.A., Bond, J.A. 2016. Transfer and expression of ALS inhibitor resistance from Amaranthus palmeri to an A. spinosus X A. palmeri hybrid. Weed Science. 64(2):240-247.

Interpretive Summary: Pigweed (Amaranthus palmeri) with resistance to the herbicide glyphosate and acetolactate synthase inhibitors has transferred that resistance to a related species by hybridization. Scientists in the USDA-ARS Crop Production Systems Research Unit, Stoneville, MS conducted research to determine the level of resistance expressed in the resistant hybrids. The results showed that the hybrids had high levels of resistance to both herbicides. These results are important because they alert farmers and industrial representatives to the need to control related species in both field and non crop areas to avoid transfer of resistance genes.

Technical Abstract: Transfer of herbicide resistance among closely related weed species is a topic of growing concern. An Amaranthus palmeri X A. spinosus hybrid was confirmed resistant to several ALS inhibitors including imazethapyr, nicosulfuron, pyrithiobac and trifloxysulfuron. Enzyme assays indicated that the ALS enzyme was insensitive to the herbicide and sequencing revealed the presence of a known resistance conferring point mutation, Trp574Leu. Alignment of the ALS gene for A. palmeri, A. spinosus, and putative hybrids revealed the presence of A. palmeri ALS sequence in the hybrids rather than A. spinosus ALS sequences. In addition, sequence upstream of the ALS in the hybrids matched A. palmeri and not A. spinosus. The potential for transfer of ALS inhibitor resistance by hybridization has been demonstrated in the greenhouse and in field experiments. This is the first time it has been documented to occur in the field without intervention. These results highlight the need to control related species in both field and non crop areas to avoid transfer of resistance genes.