Abstract
This study was carried out to examine the base temperature to flowering and the average days to flowering by accumulated hours of low temperature ($5.0^{\circ}C$) or changing temperature after bud breaking. Over-all, the prediction of flowering time in the commercial apple cultivars ('Fuji' and 'Tsugaru') and apple cultivars ('Chukwang', 'Gamhong', 'Hongan', 'Honggeum', 'Hongro', 'Hongso', 'Hwahong', 'Summer dream', 'Sunhong') bred in Korea at the Gunwi region for 4 years (from 2009 to 2012) was investigated. Also, this study estimated the flowering time when the air temperature of Gunwi region rises at $5.0^{\circ}C$ was investigated using the same data. The range of accumulated hours of low temperature (chilling requirement) was from 0 hour to 1,671 hours, and the range of high temperature (heat requirements) to flowering after low temperature treatment was from $5.0^{\circ}C$ to $29.0^{\circ}C$. The treatments of changing temperature after bud breaking were classified as constant temperature treatment (control) and $5.0{\sim}10.0^{\circ}C$ elevation or descent treatments. The results show that the average days to flowering was longer with shorter accumulated hours of low temperature, and the average days from bud breaking to flowering of 0 hour treatment was longer about 2~4 weeks than that of 1,335~1,503 hours treatments. In comparing to apple cultivars, the all cultivars were not flowered under $10.0^{\circ}C$ after bud breaking, and the cultivars with low chilling requirements needed low heat requirements for flowering. The average days to flowering of treatments that the air temperature after bud breaking was controlled about $15.0^{\circ}C$ was shorter about 1~3 weeks than that of treatments was controlled about $10.0^{\circ}C$. In the treatment of changing temperature after bud breaking, the average days from bud breaking to flowering of temperature elevation treatment was shorter than that of constant temperature treatment. By use of these results, the base temperature to flowering of main apple cultivars in Korea was seemed to $10.0^{\circ}C$, and if the air temperature of Gunwi region rises about $5.0^{\circ}C$ than that of current, the flowering time was estimated to be delayed by 1 week.
본 시험은 품종별 개화가 가능한 기준온도와 저온($5.0^{\circ}C$) 누적시간 및 발아 후 변온에 따른 평균 개화소요일수를 구명하여 국내 주요 사과품종('후지', '쓰가루')들과 국내에서 육성한 품종('추광', '감홍', '홍안', '홍금', '홍로', '홍소', '화홍', '섬머드림', '선홍')들의 개화기를 예측하고자 군위지역에서 4년(2009-2012년)동안 조사하였다. 또한, 이들 자료를 이용하여 군위 지역 기온이 현재보다 $5.0^{\circ}C$ 상승되었을 때의 개화시기를 추정하였다. 저온($5.0^{\circ}C$) 누적시간(저온요구도)의 처리 범위는 0~1,671hr 정도였고, 저온 처리 후 개화를 위한 고온(고온요구도) 처리 범위는 $5.0{\sim}29.0^{\circ}C$ 정도였다. 발아 후 변온 처리구들은 항온구(대조구), $5.0{\sim}10.0^{\circ}C$ 상승구 및 하강구로 분류하였다. 결과를 살펴보면, 저온에서의 누적시간이 짧을수록 개화소요일수가 길어지는 경향이 있었으며, 0hr 처리구의 발아 후 개화까지의 소요된 일수는 1,335~1,503hr 처리구보다 2~4주 정도 길었다. 품종 별로는 모든 품종이 발아 후 기온이 $10.0^{\circ}C$ 미만일 때 개화를 하지 못하였고, 저온요구도가 낮은 품종일수록 개화에 필요한 고온요구도가 낮았다. 발아 후 기온을 $15.0^{\circ}C$로 조절된 처리구들의 개화소요일수는 $10.0^{\circ}C$ 처리구들보다 1~3주 정도 빨랐다. 발아 후 변온 처리에서는 발아 후 기온 상승 처리구들의 발아 후 개화까지 소요된 일수가 항온 처리구보다 짧았다. 이상의 결과를 종합해보면, 국내 주요 사과품종들의 개화 기준온도는 $10.0^{\circ}C$로 생각되었으며, 군위지역의 기온이 지금보다 $5.0^{\circ}C$ 정도 상승된다고 가정하면, 개화기는 1주 정도 지연될 것으로 예측되었다.