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Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/5/2013 Publication Date: 1/23/2014 Citation: Thyssen, G.N., McCarty, J.C., Li, P., Jenkins, J.N., Fang, D.D. 2014. Genetic mapping of non-target-site resistance to a sulfonylurea herbicide (Envoke®) in Upland cotton (Gossypium hirsutum L.). Molecular Breeding. 33:341-348. Interpretive Summary: Weed management is very important to cotton production. Weeds in a cotton field are usually controlled by spraying either selective or general herbicides. Envoke® herbicide (active ingredient trifloxysulfuron sodium) kills broad-leaf weeds such as morning glory by inhibiting acetolactate synthase (ALS) activity. Most cotton cultivars are resistant to Envoke® herbicide, however, we discovered that the cultivar Paymaster HS26 is susceptible to this herbicide. Resistance to ALS-inhibiting herbicides, such as Envoke®, can be due to mutations in the target gene itself. Alternatively, plants may exhibit herbicide tolerance through reduced uptake and translocation or increased metabolism of the herbicide. In this study we generated a mapping population between susceptible HS26 and resistant cotton cultivar Stoneville 474. We found that both cultivars possess identical and sensitive ALS sequences; however, the segregation of resistance in the F2 progeny was consistent with a single dominant gene. We identified closely linked genetic markers and approximate physical location on chromosome 20 of the source of Envoke® susceptibility in the cotton cultivar Paymaster HS26. Our data suggest that a single dominant gene located on chromosome 20 is the source of tolerance to ALS-inhibiting herbicides in cotton, but it is neither ALS nor a P450 protein. Identification of this genetic mechanism will provide new opportunities to exploit sulfonylurea herbicides for management of both weeds and crop plants. Technical Abstract: Acetolactate synthase (ALS) is responsible for a rate limiting step in the synthesis of essential branched chain amino acids. Resistance to ALS-inhibiting herbicides, such as trifloxysulfuron sodium (Envoke®), can be due to mutations in the target gene itself. Alternatively, plants may exhibit herbicide tolerance through reduced uptake and translocation or increased metabolism of the herbicide. The diverse family of cytochrome P450 proteins has been suggested to be a source of novel herbicide metabolism in both weed and crop plants. In this study we generated a mapping population between susceptible and resistant cotton (Gossypium hirsutum L.) cultivars. We found that both cultivars possess identical and sensitive ALS sequences; however, the segregation of resistance in the F2 progeny was consistent with a single dominant gene. Here we report the closely linked genetic markers and approximate physical location on chromosome 20 of the source of Envoke® susceptibility in the cotton cultivar Paymaster HS26. There are no P450 proteins in the corresponding region of the reference G. raimondii Ulbr. genome, suggesting that an uncharacterized molecular mechanism is responsible for Envoke® tolerance in G. hirsutum. Identification of this genetic mechanism will provide new opportunities to exploit sulfonylurea herbicides for management of both weeds and crop plants. |
