|CARBONARI, CAIO - UNIVERSIDAD DE SAO PAULO|
|LATORRE, DEBORA - UNIVERSIDAD DE SAO PAULO|
|GOMES, GIOVANNA L.G.C. - UNIVERSIDAD DE SAO PAULO|
|VELINI, EDIVALDO - UNIVERSIDAD DE SAO PAULO|
|Pan, Zhiqiang - Peter|
Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2015
Publication Date: 1/5/2016
Publication URL: http://handle.nal.usda.gov/10113/62410
Citation: Carbonari, C., Latorre, D.O., Gomes, G., Velini, E., Owens, D.K., Pan, Z., Dayan, F.E. 2016. Resistance to glufosinate is proportional to phosphinothricin acetyltransferase expression and activity in LibertyLink® and WideStrike® Cotton. Planta. 243:925-933. DOI 10.1007/s00425-015-2451-3
Interpretive Summary: Glufosinate is a non-selective herbicide. Transgenic crops have been made resistant to this herbicide by inserting a microbial gene encoding for phosphinothricin acetyltransferase (PAT) that rapidly deactivates glufosinate by acetylating it. The expression of gene encoding PAT is very high in the LibertyLink® cotton cultivars that are commercialized as herbicide resistant varieties. On the other hand, the expression of PAT is much lower in the WideStrike® cultivars that have been commercialized for their insect-resistant trait. However, farmers sometimes use glufosinate on these latter cultivars. We determined that the difference in expression and activity of PAT can lead to crop injury in the insect-resistant variety. Therefore, farmers should be extremely careful in using glufosinate on cultivars not expressly designed and commercialized as resistant to this herbicide.
Technical Abstract: LibertyLink® cotton cultivars are engineered for glufosinate resistance by overexpressing the bar gene that encodes phosphinothricin acetyltransferase (PAT), whereas the insect-resistant WideStrike® cultivars were obtained by using the similar pat gene as a selectable marker. The latter cultivars carry some level of resistance to glufosinate which enticed certain farmers to select this herbicide for weed control with WideStrike® cotton. The potency of glufosinate on conventional FM 993, insect-resistant FM 975WS, and glufosinate-resistant IMACD 6001LL cotton cultivars was evaluated and contrasted to the relative levels of PAT expression and activity. Conventional cotton was sensitive to glufosinate. The single copy of the pat gene present in the insect-resistant cultivar resulted in very low RNA expression of the gene and undetectable PAT activity in in vitro assays. Nonetheless, the presence of this gene provided a good level of resistance to glufosinate in terms of visual injury and effect on photosynthetic electron transport. The injury is proportional to the amount of ammonia accumulating. The strong promoter associated with bar expression in the glufosinate-resistant cultivar led to high RNA expression levels and PAT activity which protected this cultivar from glufosinate injury. While the insect-resistant cultivar demonstrated a good level of resistance to glufosinate, its safety margin is lower than that of the glufosinate-resistant cultivar. Therefore, farmers should be extremely careful in using glufosinate on cultivars not expressly designed and commercialized as resistant to this herbicide.