This study was conducted over a 3-year period from 2013 to 2015 in the mid-northern inland, Cheolweon, Korea, to investigate changes in flowering date, daily mean temperature during grain filling, and yield characteristics affected by transplanting date in an early-maturing rice variety, ‘Joun’. Thirty-day-old seedlings were transplanted at four different dates at 15-day interval from May 5 to June 19. Flowering dates were July 16, July 21, July 31, and August 14 when transplanting was performed on May 5, May 20, June 4, and June 19, respectively. Late transplanting resulted in higher daily mean temperature before flowering but late-transplanted rice required fewer days and lower cumulative temperature to reach flowering from transplanting. As transplanting was delayed, daily mean temperature for 40 days after flowering decreased, whereas daily sunshine hours for the same period increased, with a temperature of 24.8°C and sunshine for 5.8 hours being recorded at the transplanting on May 5, and with a temperature of 21.0°C and sunshine for 7.7 hours at the transplanting on June 19. With late transplanting, panicles per square meter significantly decreased, whereas spikelets per panicle showed an increasing trend. Regression analysis showed that maximum head rice yield was attained from the transplanting on May 18, for which the flowering date was July 21, and daily mean temperature for 40 days from that flowering date was 24.6°C. A decrease in head rice yield by 5% and 10% of the maximum was observed for rice transplanted on June 6 and June 15, which resulted in flowering dates of August 2 and August 11, respectively, and the daily mean temperatures for 40 days from flowering were 23.2 and 21.7°C, respectively. Therefore, in mid-northern inland, it is recommended to transplant ‘Joun’ on May 18 to induce flowering on July 21, when grain filling is subjected to a daily mean temperature of 24.6°C during active filling stage.

조운은 농촌진흥청 국립식량과학원에서 벼 수확기의 분산 및 이른 추석에도 안정적으로 생산할 수 있는 평야지적응 조생종을 육성할 목적으로 1996년 조숙이면서 양질 내병 다수성 계통인 SR14880-173-3-3-2-2-2와 초형이 우수하며 수량성이 높은 단간 조생인 운봉20호를 교배하여 2009년 육성한 평야지적응 극조생 단간 내도열병 고품질 벼 품종으로 주요 특성과 수량성을 요약하면 다음과 같다. 1. 보통기 보비재배에서 출수기는 7월 23일로 오대벼보