Target site–based penoxsulam resistance in barnyardgrass (Echinochloa crus-galli) from China

Abstract

Barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is acknowledged to be the most troublesome weed in rice fields in Anhui and Jiangsu provinces of China. It cannot be effectively controlled using certain acetolactate synthase (ALS)-inhibiting herbicides, including penoxsulam. Echinochloa crus-galli samples with suspected resistance to penoxsulam were collected to identify the target site–based mechanism underlying this resistance. Populations AXXZ-2 and JNRG-2 showed 33- and 7.3-fold resistance to penoxsulam, respectively, compared with the susceptible JLGY-3 population. Cross-resistance to other ALS inhibitors was reported in AXXZ-2 but not in JNRG-2, and occasionally showed higher sensitivity than JLGY-3. In vitro ALS activity assays revealed that penoxsulam concentrations required to inhibit 50% of ALS activity were 11 and 5.2 times greater in AXXZ-2 and JNRG-2, respectively, than in JLGY-3. DNA and predicted amino acid sequence analyses of ALS revealed Ala-205-Val and Ala-122-Gly substitutions in AXXZ-2 and JNRG-2, respectively. Our results indicate that these substitutions in ALS are at least partially responsible for resistance to penoxsulam.

Investigating the resistance levels and mechanisms to penoxsulam and cyhalofop-butyl in barnyardgrass (Echinochloa crus-galli) from Ningxia Province, China

“…Penoxsulam-resistant Echinochloa spp. were reported in various rice-growing regions of China, including Jiangsu, Anhui, Hubei, Hunan, Jiangxi, and Heilongjiang provinces (Chen et al 2016;Fang et al 2019a;Liu et al 2019;Yang et al 2013). Xia et al (2016) also reported E. crus-galli populations from Hubei Province that had developed resistance to the ACCase inhibitor metamifop.…”

“…Furthermore, it was demonstrated that any of the ALS gene copies could host the ALS-inhibitor resistance mutation (Deng et al 2017;, which may also be the reason why these weeds are prone to develop resistance to ALS inhibitors. The Ala-122-Gly/Asn, Ala-205-Val, Trp-574-Leu, and Ser-653-Asn mutations in ALS have been reported to confer resistance to ALS-inhibiting herbicides in E. crus-galli (Fang et al 2019a;Matzenbacher et al 2015;Panozzo et al 2013Panozzo et al , 2017. In addition, the NTSR mechanism was reported in various ALS inhibitor-resistant weeds, such as E. crus-galli, D. sophia, and giant chickweed [Myosoton aquaticum (L.) Moench] (Bai et al 2019;Fang et al 2019b;Yang et al 2016).…”

Rice safety and control of penoxsulam-resistant and -susceptible barnyardgrass (Echinochloa crus-galli) populations with soil-applied herbicides

“…Barnyardgrass, an allohexaploid grass, has always been considered the most troublesome weed species in rice production in China (Fang et al 2018(Fang et al , 2019a(Fang et al , 2019b. Season-long competition of barnyardgrass can cause as much as 80% rice yield reduction (Ntanos and Koutroubas 2000;Smith 1988).…”

“…Unfortunately, the chance is high that barnyardgrass will become resistant to ALS inhibitors (Powles and Yu 2010). During the last decade, resistance to ALS-inhibiting herbicides has increased drastically in various cropping systems (Fang et al 2019a(Fang et al , 2019bHeap 2020;McCullough et al 2016aMcCullough et al , 2016bPowles and Yu 2010;Yu et al 2020a). To date, a total of 165 weed species worldwide have been found to be resistant to at least one of the five ALS inhibitor chemical families (Heap 2020).…”

“…; Ottis et al 2003;Khare et al 2014;Willingham et al 2008). Unfortunately, the extensive use of this herbicide in rice has caused resistant barnyardgrass populations in China (Chen et al 2016;Fang et al 2019a), South Korea (Won et al 2014), the United States (Norsworthy et al 2014;Wilson et al 2014), andVietnam (Duy et al 2018).…”