Johnsongrass is a troublesome weed infesting spring summer crops. Poor control of johnsongrass after fluazifop-p-butyl treatments has been reported in central to northern Italy. Greenhouse and outdoor dose response experiments revealed that four populations were highly resistant to fluazifop-p-butyl. All four were, cross-resistant to other aryloxyphenoxypropionate (FOP) herbicides propaquizafop, quizalofop, and haloxyfop. The resistance indexes ranged between 8 and 25 for propaquizafop and quizalofop, whereas a greater variability between populations was detected in response to haloxyfop. Conversely, cycloxydim and clethodim determined only a shift in the susceptibility with resistance index (RI) values of 2 to 3. Molecular analyses revealed that resistant plants possessed an insensitive acetyl coenzyme-A carboxylase (ACCase) target enzyme due to an Ile-to-Asn substitution at codon 2041. To our knowledge, this is the first report of such a mutation endowing ACCase resistance in johnsongrass. A molecular marker (CAPS assay) was developed for its rapid detection. Alternative mode of action herbicides S-metolachlor and nicosulfuron controlled all the FOP-resistant populations. Only a few chemical options are still available, and they have different efficacy on germinating seeds and sprouting rhizomes. To maintain efficacy over time, herbicides should be integrated with agronomic practices.
Target-Site ACCase-Resistant Johnsongrass (Sorghum halepense) Selected in Summer Dicot Crops
Scarabel L;Panozzo S;Sattin M
2014
Abstract
Johnsongrass is a troublesome weed infesting spring summer crops. Poor control of johnsongrass after fluazifop-p-butyl treatments has been reported in central to northern Italy. Greenhouse and outdoor dose response experiments revealed that four populations were highly resistant to fluazifop-p-butyl. All four were, cross-resistant to other aryloxyphenoxypropionate (FOP) herbicides propaquizafop, quizalofop, and haloxyfop. The resistance indexes ranged between 8 and 25 for propaquizafop and quizalofop, whereas a greater variability between populations was detected in response to haloxyfop. Conversely, cycloxydim and clethodim determined only a shift in the susceptibility with resistance index (RI) values of 2 to 3. Molecular analyses revealed that resistant plants possessed an insensitive acetyl coenzyme-A carboxylase (ACCase) target enzyme due to an Ile-to-Asn substitution at codon 2041. To our knowledge, this is the first report of such a mutation endowing ACCase resistance in johnsongrass. A molecular marker (CAPS assay) was developed for its rapid detection. Alternative mode of action herbicides S-metolachlor and nicosulfuron controlled all the FOP-resistant populations. Only a few chemical options are still available, and they have different efficacy on germinating seeds and sprouting rhizomes. To maintain efficacy over time, herbicides should be integrated with agronomic practices.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
