Determination Of Butachlor Resistant Echinochloa Crus-galli(L.)Occurring In Paddy Rice And Study Of The Resistant Mechanism

The present status of butachlor resistance of Echinochlor crus- galli(L.)Beauv.(CE) occurring in paddy rice in north and south of China was studied, and the resistant mechanism from the point of metabolism was studied. With continuing application of butachlor in the fields of Hubei and I-Ieilongjiang Provinces, it was noticed that the herbicidal efficacy for controlling EC was reduced. Seeds of different EC populations collected from 6 sites (Yueyang, no butachlor applied, Team III on Zhanghuyuan Farm with 14-year application of butachlor, Team IV on Zhanghuyuan Farm with 18-year application of butachlor in the south; Mudanjiang, no butachlor applied, Minzhu with 10-year application of butachlor, Acheng with 1 4-year application of butachlor in the north)were tested to evaluate butachlor resistant status in the areas. It was revealed that LC~0 for controlling of Yueyang population was the lowest, that of Mudanjiang population was the highest among the six populations, 54.73 g a.i./ha and 1271.6 g a.i.Iha respectively. The order of sensitivity of the populations from high to low ranged: Yuyang, Acheng, Team III, Minzhu, Team IV, Mudanjiang. Using Yuyang population as the control, RI indexes of other populations excluding Mudanjiang population were Acheng 5.21, Team III 5.85, Minzhu 8.00, Team IV 12.01, which indicated that the four populations had evolved resistance to bubachlor. Three seedling stages was selected to test glutathione S-transferase(GST) activity and the amount of GSH, cysteine, and whether it was correlative with LC50 values were studied. Biochemical tests showed that (1) when the seedlings of EC were treated with butachlor (5 ppm) for 48 hours, GSTs activities increased, the amount of GSH, cysteine show significant difference. The amount of GSH of treated populations was positively correlative to LC0 for controlling of the populations in the south, the amount of Cysteine of treated populations was negatively correlative to LC50 in the north. (2) The seedlings of EC were treated with butachlor (Sppm) for 9 days, compared to the untreated populations, the GSTs (CDNB) activities of eachtreated population were higher with exception of Acheng population, but the amountof GSH varied significantly according to the different populations. There was lineartrend between the GSH and LC, i.e. y=0.032l+25.029 (R2=0.8382). (3) GSTsactivity and the amount of GSH of the unbeated seedlings grown for l4 days showedpositive correlation to LC,, for controlling of the POpulations in the southrespectively, but negative correlation to LC,, of those in the north. Although GS-butachlor was not found in vivo study, it was confirmed in vitro conjugating tests byTLC and mass spectrum techniques. The free thiols and GSTs activities to CDNB inEC populations indicatCd that butachlor resistance in EC was increased notably.GSTs activity or the amoun of GSH showed direct correlation with the LC,, fOrcontrolling of different poPulations to some extent. It is suggested that the analysismethod needs to be improved, studying of other possible mechanism is needed.