This study was conducted to evaluate Korean rice cultivars to search any suitable varieties for the northern region of the Korean Peninsula (North Korea). A total of 92 rice varieties which included 74 bred cultivars from South Korea, 13 collections from North Korea and five local cultivars from China, were involved in the evaluating trials for their performance. Stability at three sites inthe northeastern areas of China, which are located in the northern border areas of North Korea, for three years from 2017 to 2019. The ecologically well-adapted rice varieties were selected at each trial site during the first year and employed again as the materials for the subsequent yield trials. A total of six varieties with relatively better performing and stability were selected through the subsequent trials at three sites for three years: Unkwang, Daejin and Taebaek at Dandong region; Hanseol and Taebong at Longjin region; Taebong and Namweon at Hunchun region, respectively. Dandong is located in the southeast parts of Liaoning, which has similar climatic characteristics to the west coastalregion of North Korea. Longjin is located in the middle-east parts of Jilin, which has also similar climatic characteristics to the northern inland region of North Korea. Hunchun is located in the northeastern parts of Jilin, which has presumably similar climatic characteristics to the northern part of the eastern coastal region of North Korea. Unkwang is characterized by its early maturity, with the heading at the 2nd of August, and reveals a yield potential of 7.11 T/ha with resistance to the blast (BL) and the bacterial leaf blade (BLB) diseases. It is predicted to be suitable for the northern area of the Suyang mountain region and the central inland region of North Korea. Daejin has asemi-early maturity heading around the 6th of August and yields of 6.06 T/ha with resistance to BL, BLB, and stripe virus (SV) diseases. Daejin will be adaptable to the northern area of Suyang mountain region. Taebaek is medium maturing variety of Indica/Japonica type. It is heading at the 14thof August with good ripening at maturity, and has yield potential of 6.84 T/ha with resistance to BL, BLB and SV diseases. It will be adaptable to the southern area of Suyang mountain region. Hanseol is early maturing, heading on the 3rd of August, and yields 6.44 T/ha with the short stature and cold tolerance (CT). It will be adaptable to the northern inland and mountainous regions of North Korea. Taebong is semi-early maturingwith the heading at the 6th of August and has a yield potential of 6.96 T/ha with cold tolerane and blast resistance. Taebong was also outstanding in theHunchun region, indicating a more or less wide adaptability in cold areas. It is expected to be adaptable to the northern inland region of North Korea as well as the northern part of the eastern coastal region. Namweon is a medium-maturing variety with aheading date of August 10, and a yield potential of 4.76 T/ha with cold tolerance and resistance to rice neck blast disease. It is expected to be adaptable to the northern part of the eastern coastal region.

1. 본 연구는 우리나라 북부지역과 중국의 북한 인접지역에서 동일 품종을 재배하여 다양한 기후조건에서도 출수일수 변이계수가 안정적이고 조숙성인 품종을 선정하여 북한 적응성이 높은 품종선발에 기초자료로 활용하고자 수행된 연구결과이다. 2. 북한 접경 국내외 6개소에서 출수일수별로 극조생종, 조생종, 준조생종, 중생종의 4개 출수생태형으로 분류하였다. 국내에서는 극조생종에는 9품종, 조생종은 42품종, 준조생종은 17품종, 중생종은 4품종으로 분류되었고 중국에서는 극조생종 7품종, 조생종 27품종, 준조생종 32, 중생종 9품종으로 구분되었다. 3. ‘수원’ 등 국내 3개소에서 출수기의 변이계수는 4.8~ 18.5%이었고 변이계수가 6.0 이하인 품종은 태봉, 내풍, 화동, 운장, 인월, 진봉, 운봉, 금영, 삼천 등 이었다. 4. ‘단동’ 등 중국 3개소에서 출수기의 변이계수는 국내보다 낮은 0.5~8.1%로 변이계수가 2.0 이하인 품종은 태성, 진부찰, 중모1001, 오봉, 새상주, 중모1011, 삼천, 남원, 길주1호(북한 수집) 등 이었다. 5. 한국과 중국의 6개소에서 출수기 변이계수는 8.7~13.3% 의 범위를 보였고, 변이계수가 9.0% 이하로 낮은 품종은 국내 육성 품종 둔내, 운봉, 화동, 진부찰, 설레미 품종으로 북한의 벼 재배지역에서 적응성이 높을 것으로 판단된다. 대비품중으로 북한 대비품종인 원산69호, 중국 대비품종인 길주1호 등도 변이계수가 안정적인 품종이었다.

Rice production in Korea has markedly increased during the last two decades due to newly developed high yielding varieties and improved production technology. This experiment was conducted to determine the potential of tropical japonica germplasm in enhancing the yield of temperate japonica. The yield performance of two tropical japonicas (IR 65597-29-3-2 and IR66154-52-1-2) and one temperate japonica (Dongjinbyeo) was compared at different plant densities and nitrogen levels under Korean environmental conditions. Although tropical japonicas showed low tillering habit and large panicles, they had similar leaf area index and dry weight at heading stage to Dongjinbyeo of the high tillering type indicating that there was not much difference between tropical and temperate japonica in terms of biomass production. The highest milled rice yield of 6.15 t/ha was obtained from Dongjinbyeo at a high nitrogen level with less planting density (220 kg N/ha and 30 ~times 15 cm). However, those of the two tropical japonicas were 5.36 t/ha at the condition of 165 kg N/ha and 30 x 10 cm planting density and 5.06 t/ha at the condition of 165kgN/ha and 15 x 15 cm planting density, respectively. Ripened grain of tropical japonicas ranged from 65 to 87%, while that Dongjinbyeo ranged from 82 to 97% under Korean conditions.

Spikelet and vascular bundle development in rice panicles is considered to be the important elements in determining the genotype's yield capacity and translocation ability of assimilates into grains, respectively. This study was conducted to clarify the varietal differences of the spikelet and vascular bundle formations among three rice cultivars; Iksan 435 (japonica), Dongjinbyeo (japonica) and Namcheonbyeo (Tongl-type). Iksan 435 had more primary rachis branches (PRBs), secondary rachis branches (SRBs) and spikelets per panicle than Dongjinbyeo, but less than Namcheonbyeo. Among three cultivars, Namcheonbyeo showed the highest spikelet number per panicle which were differentiated SRBs mainly on PRBs of lower rachis nodes. And Namchenbyeo showed the highest number of large vascular bundle (LVB) as well as small vascular bundle (SVB) and it displayed the largest diameter of LVB. Between the two japonica cultivars, the numbers of LVBs end SVBs were significantly higher in Iksan 435 than those in Dongjinbyeo. The PRBs to LVBs ratio of Namcheonbyeo was twice as large as those of Dongjinbyeo and Iksan 435. These results indicate that the newly bred cultivar, Iksan 435, has improved yield capacity by increasing the number of especially rachis branches and spikelets formation as well as 1,000 grain weight, compared to other former japonicas

Over 2,000 ha of rice fields in the western and southern coastal region of Korea were flooded with sea water during the spring tide, on August 19-21, 1997, and the rice plant at heading stage was injured. The field surveys were undertaken at the sea water flooded paddy fields in Chonbuk Province, to identify the injury symptoms and rice yield damage subjected to different flooding condition and desalinization methods. Five days after sea water flooding at heading stage, the flag leaves of rice plants flooded with 30 ㎝ deep sea water withered from the tip, the withering progressed to the lower leaves in deeper flooding. The spikelets were spotted black and discolored from the tip at 50 ㎝ deep flooded rice, and some panicles changed to white at 80 ㎝ deep flooded rice. Most of the rice leaves submerged completely for an hour were withered and most of panicles changed to white. The milled rice yield, percentage of ripened grain, and 1000 grain weight of flooded rice decreased with deeper flooding water, higher water salinity and longer flooding time. Even under the same flooding conditions, the damage of rice yield varied with the growth stage: heading stage>dough stage>booting stage. Rice yield damage was less in the fields on the upper riverside than those of the fields on the estuary and seaside, because of lower water salinity. In a flooded field, the rice yield damages were reduced as the distance increased from the levees where the sea water inflowed and increased as the distance increased from the fresh water irrigation gate. The desalinization treatments consisting of frequent exchange of irrigation water and spraying with fresh water soon after flooding effectively reduced the rice yield damage.

수도 9개 품종을 이용하여 이면교잡에 의한 36개 조합의 F1 및 F2 세대에서 간장, 수장, 수수에 관여하는 잡종강세 정도와 유전자분포상태를 검정하였던 바 그 결과를 요약하면 다음과 같다. 1. 간장의 잡종강세 정도는 F2 세대보다는 F1 세대에서 크고, SR7796-9, SR7796-44품종이 교배친으로 되어 있는 조합에서는 간장이 긴 쪽으로 현저한 Heterobeltiosis를 나타낸 조합이 많았다. 2. 수장에 있어서도 Heterosis와 Heterobeltiosis의 정도는 F1 세대에서 F2 세대보다 크고, ZLAYN, Arborio 품종이 교친으로 되어 있는 조합에서 수장이 긴 쪽으로 Heterobeltiosis를 나타낸 조합이 많았다. 3. 수수에 있어서도 F1 세대의 Heterosis 정도가 F2 세대보다 현저히 높았고, IR 747B2 -6, SR8234-17, SR8772-29품종이 교배친으로 되어있는 조합에서 Heterobeltiosis가 나타난 조합이 많았다. 4. 간장은 F1 , F2 세대 모두 불완전우성을 나타내었으며, 장간은 단간에 비하여 우성을 나타내었으나IR747B2 -6는 단간이 우성을 나타내었다. 5. 수장은 세대에서 불완전우성을 나타내었으며 품종에 따라 우열의 정도가 달랐다. 6. 수수에 있어서도 F1 , F2 세대 모두 불완전우성을 나타내었고, 대체적으로 수수가 적은 것이 많은 것에 비하여 우성이었다.

우리나라에서 재배하고 있는 면화 품종 목포005, Red leaf, Paymaster, Acala 1517w 등에 대하여 수정현상과 면모발생 및 발육에 관해서 비교조사하였다. (1) 화분은 수분 4시간후부터 발아신장하고, 수분 10시간이면 화주의 기부에 달하고 수분 18시간이면 태좌를 거쳐 주공에 진입한다. (2) 화분관이 주공에 진입할때는 1개의 매조세포를 뚫고 들어가기 때문에 수정후에는 1개의 매조세포만 남는다. (3) 수분 18-485시간이면 수정이 전부 완료되는데 목포 005가 빠르고 Paymaster는 늦으며 Red leaf는 그 중간이다. (4) 면모는 표피세포의 분열에 의하여 생긴 낭세포가 신장하는데 개화전부터 시작한다. (5) 면모는 수분후 1시간에 발생수가 가장 많아 약 60-80%이고 4-6시간에 거의 완료되는데 배주의 상부보다 기부에 많고 내측면보다 외측면에 많다. (6) 평균 면모장은 수분 1시간이면 2.7-8.3u m , 수분 4-48시간이 되면 43.8-263.7u m 신장하는데 목포 005, Red leaf는 신장속도가 거의 같고 Paymaster는 늦은 편이다.