Resistance to ACCase Inhibitor Cyhalofop-butyl in Echinochloa oryzicola Collected in Gyeongsangnam-do Province of Korea

Repeated use of ACCase inhibiting herbicides for a long time has resulted in increases of resistant Echinochloa oryzicola populations in paddy fields in middle west area of Korea. This study aims to investigate current status of herbicide resistant E. oryzicola in Gyeongsangnam-do, in which there is less information about herbicide resistance. For resistance frequency and dose-response study, seeds from 100 individual plants of E. oryzicola in Gyeongsangnam-do were collected and tested with cyhalofop-butyl. Seven percent of plants from Gyeongsangnam-do was resistant at a recommended rate of cyhalofop-butyl. $GR_{50}$ values (herbicide rates required to reduce plant growth 50%) for one representative resistant populations and five susceptible populations were $738g\;a.i.\;ha^{-1}$ and 66-234 (average 147)$g\;a.i.\;ha^{-1}$, respectively, indicating average 5 times difference in resistance. Although lower rate of frequency of herbicide resistance in Gyeongsangnam-do than in Jeollabuk-do, increases of herbicide resistance are expected in this area because of increases of direct seeded rice fields and increases of dependence on a specific herbicide. Therefore, it is necessary to monitor herbicide resistance regularly and conduct integrated herbicide resistance management in this area.

ACCase 저해 제초제 cyhalofop-butyl에 대한 경남지방 수집종 피의 저항성

경남지역 제초제 저항성 피의 발생현황과 저항성 정도를 알아보기 위하여 벼 재배 논에서 100개체의 피 종자를 수집하여 ACCase 저해제인 cyhalofop-butyl에 대한 약량반응 실험을 수행한 결과, 수집한 피의 7%가 저항성으로 조사되었다. 선발된 감수성 5개체의 $GR_{50}$값은 평균 $147g\;a.i.\;ha^{-1}$로 나타났고, 함양 지역의 저항성 개체의 $GR_{50}$값은 $738g\;a.i.\;ha^{-1}$ 로 R/S (ratio of resistance to sensitivity)값은 5.01배로 나타났다. 현재 경남지역에서의 저항성 피의 발생 수준은 낮은 것으로 나타났지만, 저항성 피의 확산을 지연시키거나 막기 위해서는 주기적인 저항성 피의 모니터링과 체계적인 저항성 잡초 관리방안을 마련하여 수행할 필요가 있다.