Jun-Hyeon Cho

Large-scale screening of rice accessions to evaluate resistance to bakanae disease

Bakanae disease is an important fungal disease in the world. No rice (Oryza sativa L.) varieties have been found to be completely resistant to this disease. To facilitate accurate, uniform and simultaneous screening of many rice accessions, we developed an inoculation method for microconidia of Fusarium fujikuroi using a tissue embedding cassette and seedling tray. Standards for evaluating the inoculated rice seedlings as healthy or unhealthy were also established. The method was fast and reproducible for accurately evaluating resistance to bakanae disease in rice.

A Waxy Black Giant Embryo Earley Maturing Rice Variety ‘Nunkeunheugchal’

Nunkeunheugchal (registration No. 01-0001-2014-4), a black waxy giant embryo rice cultivar, was developed by the rice breeding team of National Institute of Crop Science (NICS), RDA in 2012. This cultivar was derived from the cross between ge and Josaengheugchal in 2004/2005 winter season, and selected by a promising line, YR25277-B-B-314-2, was selected and designated as the line of Milyang263 in 2009. The local adaptability test of Milyang263 was carried out at four locations from 2010 to 2012 and it was named as Nunkeunheugchal. This variety is a early maturity cultivar. It has 65 cm in culm length and 72 spikelets per panicle, and 1,000 grain-weight of brown rice is 17.8 g which is less than that of Josaengheugchal. This variety is resistant to leaf blast, but susceptible to bacterial blight, neck blast, virus disease and insect pest. The yield potential of Nunkeunheugchal was about 3.54 MT/ha as brown rice at ordinary fertilizer level in local adaptability test for three years. Nunkeunheugchal possesses benefits to rice consumers because of high amounts of GABA, anthocyanin, calcium and iron. This variety would be adaptable to the paddy field of middle and southern plain region of Korea.

Differential Tolerance of Rice Cultivars to Mesotrione-Contained Herbicides

Greenhouse experiment was conducted to evaluate tolerance of six rice cultivars, three IndicaJaponica 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. to three to four leaf stage rice at 5 and 15 days after transplanting, respectively. Related study was also conducted to compare for IndicaJaponica and Japonica rice cultivars at different MP rates. Response to two herbicides varied with respect to rice cultivars and herbicide rates. All IndicaJaponica 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. 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. MP was 6~7 at 7DAT and it was also decreased to 3~8 at 14 DAT. The plant hight of IndicaJaponica rices was inhibited by 18~43% at application of 90 g a.i. MP and 30~50% at 180 g a.i. MP. The dry matter reduction was greater than that of plant height inhibition, showing 46~73% at 90 g a.i. MP and 65~82% at 180 g a.i. 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. to 180 g a.i. . 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. . Based on value determined in reduction of shoot dry weight for MP, the IndicaJaponica 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 IndicaJaponica rices were more susceptible than the Japonica rices to the MP and BMPP.

Physicochemical properties of aromatic rice prepared using different milling recoveries and roasting procedures

향미의 도정률에 따른 색도는 도정률이 증가할수록 L값은 증가하고 a 값 및 b 값은 감소하였으며, 갈색도 및 탁도는 감소하는 경향을 나타내었다. 총 폴리페놀, amylose 및 전분 함량은 도정률이 증가할수록 각각 28.11-33.84 ㎎/100 g, 24.97-31.06 ㎎/100 g 및 68.27-73.04%로 폴리페놀은 감소하고 아밀로오스 및 전분 함량은 증가하였다. 향미의 품질 향상을 위한 로스팅 처리는 시간이 증가할수록 L 값은 감소하고 a 값 및 b 값은 증가하였다. 총 폴리페놀 및 총 플라보노이드 함량은 로스팅 처리 구간에서 각각 37.41-41.65 ㎎/g 및 21.93-22.30 ㎎/g으로 무처리구간 33.00 ㎎/g 및 20.78 ㎎/g보다 전반적으로 증가하는 경향을 나타내었다. 아밀로오스 및 전분 함량 또한 로스팅 처리를 통해 25.06-26.10 g/100 g 및 76.38-81.81%로 무처리구에 비해 증가하였다. DPPH 및 superoxide radical 소거활성 및 FRAP에서는 로스팅 처리한 향미벼에서 61.56-67.78%, 43.14-52.90% 및 0.72-0.79 mM을 나타내어 무처리 구간보다 높은 소거활성을 나타내었다. 이상의 결과에서, 향미를 20% 도정한 다음 30분 로스팅 처리로 인해 가공적성 및 항산화 활성이 증진되어 식품가공용 소재로 다양하게 활용 가능할 것으로 사료된다.