Differential Tolerance of Rice Cultivars to Mesotrione-Contained Herbicides

Greenhouse experiment was conducted to evaluate tolerance of six rice cultivars, three Indica${\times}$Japonica rice (long grain, cv. Dasanbyeo, Segejinmi and Hanareumbyeo) and three Japonica rice (short grain, Nampyung, Ilpumbyeo and Junamjosaeng) cultivars, to mesotrione+pretilachlor (MP) and bensulfuron-methyl+mesotrione+pretilachlor+pyriftalid (BMPP) in transplanting rice. Two herbicides were applied at 90 g and 180 g a.i. $ha^{-1}$ to three to four leaf stage rice at 5 and 15 days after transplanting, respectively. Related study was also conducted to compare $GR_{50}$ for Indica${\times}$Japonica and Japonica rice cultivars at different MP rates. Response to two herbicides varied with respect to rice cultivars and herbicide rates. All Indica${\times}$Japonica rice cultivars exhibited susceptible to both MP and BMPP as reflected by increased visual injury, shorter plant height and higher plant dry matter reduction when compared with nontreated rice cutlivars. The degree of foliar chlorosis by MP at 90 g a.i. $ha^{-1}$ was 5~6 at 7 days after treatment(DAT) but it was decreased to 3~6 at 14DAT. The degree of leaf chlorosis treated with 180 g a.i. $ha^{-1}$ MP was 6~7 at 7DAT and it was also decreased to 3~8 at 14 DAT. The plant hight of Indica${\times}$Japonica rices was inhibited by 18~43% at application of 90 g a.i. $ha^{-1}$ MP and 30~50% at 180 g a.i. $ha^{-1}$ MP. The dry matter reduction was greater than that of plant height inhibition, showing 46~73% at 90 g a.i. $ha^{-1}$ MP and 65~82% at 180 g a.i. $ha^{-1}$ MP. Similar leaf chlorosis injury and growth inhibition of rice cultivars was observed in the BMPP treatment. The injury and growth inhibition by MP and BMPP increased with increase in herbicide rate from 90 g a.i. $ha^{-1}$ to 180 g a.i. $ha^{-1}$. However, most of the Japonica cultivars are tolerant to MP and BMPP at both rates. There was no visible leaf chlorosis but plant height and dry matter production were slightly reduced at 180 g a.i. $ha^{-1}$. Based on $GR_{50}$ value determined in reduction of shoot dry weight for MP, the Indica${\times}$Japonica rice showed 12.9 fold lower compared with the Japonica rice. The result indicates that rice cultivars vary in tolerance to herbicides of MP and BMPP and Indica${\times}$Japonica rices were more susceptible than the Japonica rices to the MP and BMPP.

Mesotrione 함유 제초제에 대한 벼 생태형간 약해반응 차이

최근에 등록된 mesotrione+pretilachlor(MP) 및 bensulfuron-methyl+mesotrione+pretilachlor+pyriftalid (BMPP)에 대한 벼 생태형간 약해 반응을 조사하기 위해 통일형(장립종) 및 일본형(단립종) 각 3 품종을 표준량과 2배량을 처리하여 온실에서 포트시험한 결과는 다음과 같다. 제초제 MP 및 BMPP에 대한 약해 반응은 벼 생태형에 따라 달랐는데 통일형 품종은 모두 감수성을 보였으나 일본형 벼는 약해가 발생하지 않았다. 통일형 벼는 제초제 처리 후 5일부터 백화증상을 보였고 7일에 약해증상이 뚜렷하였으며 처리 후 14일에는 약해증상이 처리 후 7일 보다 약해지는 경향이었다. 약해정도는 처리농도가 증가할 수록 약해 발생이 심하였다. MP 및 BMPP에 대한 통일형 벼 품종의 초장 억제율은 90g a.i. $ha^{-1}$(표준량)에서 18~43%, 배량에서 30~50% 억제되었고 건물중은 초장보다 억제가 더 커 표준량에서는 46~73%, 배량에서는 65~82%가 억제되었고 억제정도는 농도가 증가할수록 컸다. 하지만 대부분의 일본형 벼는 제초제 2배에서도 약해증상을 보이지 않았으나 초장 및 건물중이 약간 억제 되었다. 벼 생태형별 MP에 대한 50% 생육억제 농도를 조사한 결과, 통일형 벼는 37g a.i. $ha^{-1}$로 일본형 벼의 476g a.i. $ha^{-1}$보다 12.9배나 낮았다. 이상의 결과에서 mesotrione을 함유하고 있는 MP 및 BMPP에 대한 벼 생태형간 반응에 차이가 있고, 초다수형 벼 재배시 초기 잡초 발아전 제초제로서 MP 및 BMPP의 사용을 자제하는 것이 바람직하다.