Bbareumi' is an extremely early maturing rice cultivar with the fastest harvesting time in Korea. To develop 'Bbareumi', 'Joami' with good quality in Chungnam plain area and 'Hokuto' originating from Japan with the fastest heading date among genetic resources were used as breeding materials. After crossing them in 2010, the 'Bbareumi' cultivar was developed using the pedigree method. A yield trial was conducted from 2015 to 2016, and a local adaptability test was conducted from 2016 to 2018. The heading date of 'Bbareumi' was seven days earlier than 'Jinbuolbyeo', showing an average of June 23 rd , and it could be harvested from the end of July to the beginning of August when transplanted early in Chungnam plain area. 'Bbareumi' had a short culm length of 63.3 cm and panicle length of 19.3 cm. Milled rice yield was approximately 4.87 MT/ha and the percentage of head rice was 89.2% under normal fertilizer condition. 'Bbareumi' will be used as a premium rice brand with newly harvested rice before 'Chooseok', Korean Thanksgiving Day and is expected to contribute to the revitalization of double-cropping in the Chungnam plain area (Registration No. 8130).
This study aimed to investigate the effect of nitrogen application methods on the yield and grain quality of an extremely early maturing rice variety. The experiment was conducted in the rice research field of Chungnam Agricultural Research and Extension Services, South Korea, in 2019 and 2020. Two nitrogen application methods, BD (100% as a basal dressing) and BTD (70% as a basal dressing + 30% as a top dressing), with three different nitrogen levels (70 kg/ha, 90 kg/ha, and 110 kg/ha), were employed. The results showed that BD treatment had comparable or higher head rice yields and improved grain quality compared to BTD treatment at all nitrogen levels. Additionally, the SPAD value at heading date was highly correlated with both the protein content (r2 = 0.838**) and glossiness of cooked rice (r2 = 0.630**). Therefore, this study suggests that BD treatment could be an effective approach to improve the productivity and quality of extremely early maturing rice varieties while saving on labor costs, and the SPAD value can be used as an index to infer the taste of rice. In conclusion, this study provides useful insights into nitrogen application methods that can be used to enhance the yield and quality of extremely early maturing rice varieties.
This study aimed to investigate how transplanting date affects the agronomic and grain quality traits of two early maturing rice varieties. The experiment was conducted in the rice research field of Chungnam Agricultural Research and Extension Services, South Korea and rice materials were transplanted at intervals of approximately 15 days from April 16 to July 16 in 2019 and 2020. Results showed that agronomic and grain quality traits varied according to the transplanting date, and earlier transplanting resulted in the longer period of days from transplanting to heading (DTH). The spikelet number m-2 was highly correlated with the milled rice yield (r = 0.963** for Jinbuol, r = 0.909** for Yeoreumi) and it significantly decreased as the transplanting date was delayed, which was leading to lower yield. Environmental factors, the mean temperature during the grain filling stage, had a negative correlation with head rice rate (r2 = 0.825** for Jinbuol, r2 = 0.803** for Yeoreumi), and the number of days from transplanting to heading showed negative correlation with protein content (r2 = 0.777** for Jinbuol, r2 = 0.833** for Yeoreumi). Therefore, increasing the number of days from transplanting to heading date can lead to higher milled rice yield and lower protein content, and avoiding heading dates on July 17 can improve the appearance traits. As a results, it is suggested that early transplanting is advantageous to increase the milled rice yield and grain quality of early maturing rice.
This study was performed to determine the optimum transplanting dates of 'Bbareumi' in the Chungnam Plain area. 'Bbareumi' was transplanted into a rice research field of Chungnam Agricultural Research and Extension Services at intervals of approximately 15 days from April 17 th to August 1 st in 2019 and 2020. The heading dates of 'Bbareumi' were June 23 rd to September 2 nd depending on transplanting dates. The highest milled-rice yield was 5.61 MT/ha on May 1 st and the lowest was 3.65 MT/ha on August 1 st . As the transplanting date was delayed, protein content increased; however, the number of days from transplanting to heading decreased. Protein content and the number of days from transplanting to heading showed a highly significant correlation (R 2 = 0.802 ** ). Therefore, it was found that early transplanting was beneficial to produce lower protein content because head rice percentage was 84-87% for early (April 17 th to May 16 th ), 74-80% normal (June 1 st to June 16 th ), and 86-95% for the late transplanting date (July 1 st to August 1 st ). The mean temperature during the ripening stage differed according to the transplanting dates, and early transplanting showed a lower temperature than the normal one (May 16 th to June 15 th ) and a higher head rice percentage. Therefore, extremely early maturing rice cultivars should be transplanted between late April and early May to obtain lower protein content and higher head rice percentage. These results will be useful for rice breeding programs, as it is generally recognized that early transplanting results in poor rice quality; however, this study revealed contrasting results.
Early maturing rice cultivars grown in plain areas have an undesirable appearance due to high temperatures during the grain-filling stage. Therefore, developing early maturing rice cultivars with desirable appearance traits in plain areas is the primary goal of rice breeding programs. This study aimed to develop an early maturing rice cultivar adaptable to early transplanting cultivation in the Chungnam plain area. To develop "Yeoreumi," two breeding materials were used, good-quality "Joami" from the Chungnam plain area and "Hokuto" having the fastest heading date among the genetic resources and originating from Japan. These two resources were crossed in 2010 to develop the "Yeoreumi" cultivar using the pedigree method. A yield trial was conducted in 2015-2016, and a local adaptability test was conducted in 2017-2019. The heading date of "Yeoreumi" was July 10, when it was transplanted early in the Chungnam plain area, and it could be harvested at August end, which was sufficient to produce a fresh stock of rice before "Chuseok, which is the Korean Thanksgiving Day." The yield of milled rice was approximately 5.29 MT/ha in the local adaptability test, which was 0.47 MT/ha higher than that of "Jinbuolbyeo." Additionally, its grain quality was good, with 89.9% head rice and 67.6 glossiness of cooked rice. Overall, the results of this study indicated that "Yeoreumi" was suitable for early transplanting cultivation in the Chungnam plain area for "Chuseok," and could be used as a representative early maturing rice cultivar in Chungcheongnam-do (Registration No. 8597).
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