Resistance Of American Sloughgrass(beckmannia Syzigachne(steud.)fernald) To Mesosulfuron-methyl

With wide and intensive use of herbicides, weed resistance becomes increasingly prominent world wide. As its high efficiency for controlling grass weeds, mesosulfuron-methyl is the most popular ALS inhibiting herbicide used in wheat fields. Since mesosulfuron-methyl was commercialized in 2002, the application amount was growing fast. According to the weed resistance monitoring, some American Sloughgrass(Beckmannia syzigachne(Steud.) Fernald) populations were not sensitive to mesosulfuron-methyl as expected. It is significant to confirm the resistance to mesosulfuron-methyl in Amer ican Sloughgrass, as it is related to the management of American Sloughgrass and the lifespan of mesosulfuron-methyl in service. The resistance level and the mechanism of resistance to mesosulfuron-methyl in American Sloughgrass populations were researched with the test material gathering from 65 sites from 7 provinces in China, Hebei, Henan, Anhui, Hubei, Jiangsu, Shandong and Sichuan. The results showed as following:1. The experiments to identify the suspected resistant populations of American Sloughgrass to mesosulfuron-methyl showed that 23 populations of American Sloughgrass were survived among the seeds collected from 65 sites from 7 provinces. The suspected resistant populations were all distributed in Anhui and Jiangsu province, whereas populations distributed in Hebei, Henan, Hubei,Shandong and Sichuan province were susceptible. In addition, the resistance of a population to mesosulfuron-methyl was developed, resulting in a higher resistant level in 2012 comparing with the population collected in 2011 in the same place.2. Dose-response experiments showed that compared to a susceptible population, the resistant populations WC11-17, WC12-10 and WC12-25 collected in Anhui and Jiangsu had 9.12-,40.59-and 12.49-fold resistance to mesosulfuron-methyl, respectively.3. The results of target enzyme activity assay revealed that the mesosulfuron-methyl I50 values for WC11-17, WC12-10 and WC12-25 were 33.33,109. 89 and 39.00, respectively, all greater than that of the susceptible population WC12-3.4. Target enzyme gene detection showed that Pro-197-Arg、Pro-197-Thr and Pro-197-Leu mutations were identi?ed in ALS extracted from WC11-17、WC12-10 and WC12-25 plants respectively.5. The experiment to detect the cross-resistance of American Sloughgrass to imazapic, pyroxsulam, flucarbazone showed that WC12-3 was sensitive to the 3 ALS inhibitors, whilst WC11-17 had 3.07-, 8.33- and 8.21-fold resistance to imazapic, pyroxsulam and flucarbazone, respectively. The results of target enzyme activity assay revealed that the imazapic, pyroxsulam and flucarbazone I50 values for WC11-17 were 3.22, 75.66, 61.72 greater than that of the susceptible population WC12-3, respectively. The population res istant to mesosulfuron-methyl with Pro-197-Arg has cross-resistance to IMI, TP and SCP ALS inhibitors,with the intensity order TP>SCP>IMI。In general, the distributions and resistant level of Amer ican Sloughgrass to mesosulfuron-methyl and the cross-resistance of one population to other three ALS inhibitors were confirmed. The mechanism that the point mutation in ALS gene results in resistance to ALS inhibitors was explained inenzyme and gene level.