Target-site cross-resistance to ALS inhibitors in johnsongrass originating from Greek cornfields

Abstract

Dicamba is a synthetic auxin herbicide that may be applied over the top of transgenic dicamba-tolerant crops. The increasing prevalence of herbicide-resistant weeds has resulted in increased reliance on dicamba-based herbicides in soybean production systems. Because of the high volatility of dicamba, it is prone to off-target movement, and therefore has been of increased concern regarding dicamba drift onto nearby specialty crops. The present study evaluates twelve mid-Atlantic vegetable crops species for sensitivity to sub-lethal rates of dicamba. Soybean, snap bean, lima bean, tomato, eggplant, bell pepper, cucumber, summer squash, watermelon, pumpkin, sweet basil, lettuce, and kale were grown in the greenhouse and exposed to dicamba at 0, 0.056, 0.11, 0.28, 0.56, 1.12, 2.24 g ae ha−1, which is respectively 0, 1/10,000, 1/5,000, 1/2,000, 1/1,000, 1/500, and 1/250 of the maximum recommended label rate for soybean application (560 g ae ha−1). Vegetable crop injury was evaluated 4 weeks after treatment using visual rating methods and leaf deformation index (LDI) measurements. Overall, snap bean was the most sensitive crop species with dicamba rates as low as 0.11 g ae ha−1 resulting in significantly higher leaf deformation levels compared to the nontreated control. Other Fabaceae and Solanaceae species also demonstrated high sensitivity to sub-lethal rates of dicamba with rates ranging 0.28 to 0.56 g ae ha−1 causing higher leaf deformation compared to the nontreated control. While cucumber, pumpkin, and summer squash were no or moderately sensitive to dicamba, watermelon showed greater sensitivity with unique symptoms at rates as low as 0.056 g ae ha−1 based on visual evaluation. Within the range of tested dicamba rates, sweet basil, lettuce and kale demonstrated tolerance to dicamba with no injury observed at the maximum rate of 2.24 g ae ha−1.

Identification of an acetyl‐CoA carboxylase‐resistant johnsongrass (Sorghum halepense L.) population from a cotton field in northern Greece

“…Based on these results, crop rotation between cotton and corn must be implemented, as nicosulfuron can be used in corn for effective control of the R johnsongrass population. However, this agronomic practice should be regarded as a short‐term solution because the risk of selecting johnsongrass populations with cross‐resistance to ALS inhibitors (Papapanagiotou et al, 2022) or multiple resistance to both ACCase and ALS inhibitors is inevitable (Scarabel et al, 2014).…”

“…It is a noxious weed responsible for severe infestations in many economically important crops (Chirita et al, 2007; Jensen et al, 2011; Mitskas et al, 2003). It is native in the Mediterranean areas of Africa, Asia (especially Syria and Turkey), and Europe (Follak & Essl, 2013), whereas in Greece it is a noxious weed in summer crops such as corn ( Zea mays L.), cotton ( Gossypium hirsutum L.), sugar beets ( Beta vulgaris L.), sunflower ( Helianthus annuus L.), and vegetables (Haitas et al, 1995; Kaloumenos & Eleftherohorinos, 2009; Mitskas et al, 2003; Papapanagiotou et al, 2022).…”

Cytochrome P450s-Involved Enhanced Metabolism Contributes to the High Level of Nicosulfuron Resistance in Digitaria sanguinalis from China

“…Among them, the SU herbicide nicosulfuron has been frequently used for POST control of grass weeds in maize fields, including D. sanguinalis [ 6 ]. Nevertheless, its excessive use has resulted in the problem of the “3Rs” (i.e., residue, resistance, and resurgence), and nicosulfuron resistance has caused major trouble in Chinese maize yields [ 6 , 7 , 8 , 9 , 10 , 11 ].…”