Rice is an important food crop that feeds most of the world's population. However, due to the increased frequency of pest outbreaks, it is necessary to cultivate complex pest-resistant rice cultivars. A mutant population was derived by culturing tissue of ‘Hwayeong’ at the Plant Molecular Breeding laboratory of Kyungpook National University in the Republic of Korea. The cultivar ‘Drimi4ho’, a line that was resistant to complex disease, was finally selected by backcrossing with ‘Junam’. The heading date of ‘Drimi4ho’ is August 11 (107 days after sowing). Drimi4ho’ has culm length of 69 cm, panicle length of 21 cm, 16 panicles per hill, 115 spikelets per panicle, a ratio of ripened grain of 92.7%, and a 1,000-grain weight of 24.3 g. No lodging occurred when ‘Drimi4ho’ was grown in the field by standard fertilization. It is also resistant to leaf/neck blast disease, bacterial blight (K₁, K₂, K₃), rice dwarf virus, rice black-streaked dwarf virus, rice stripe virus, BPH, and SBPH. ‘Drimi4ho’ is a round and short-type grain, and is very clear and transparent without chalkiness. In addition, it has excellent physicochemical properties that make up food, so its taste is good. When ‘Drimi4ho’ was planted under ordinary conditions in the southern mountainous area of Korea, the yield was 5.53 MT/ha (Registration No. 6124).

‘Seongsan’, an early multi-resistant japonica rice cultivar developed from a cross between ‘Jopyeong’ and ‘Jungmo 1012’, was developed by the rice breeding team of the National Institute of Crop Science, Rural Development Administration. The average heading date at the ordinary planting was July 25th in seven test spots. In response to physiological stresses, premature heading rate was very low and viviparous germination rate was relatively low (15.7%). In response to biotic stresses, ‘Seongsan’ showed resistance to bacterial blight pathogen K1 to K3, rice stripe virus, and blight leaf. The milled rice of ‘Seongsan’ was translucent with relatively clear non-glutinous endosperm and medium short grain. The cooked rice had good palatability compared with that of ‘Chucheong’. The milled rice yield of this variety was approximately 5.52 MT/ha in a three-year local adaptability test. ‘Seongsan’ was an early maturing multi-resistant rice with good grain quality, and it was expected to be used as a representative for maturity diversification of rice cultivation area (Registration No. 7277).

This study was conducted to develop multi-resistant lines to brown planthopper, bacterial blight, and rice stripe virus using anther culture in rice. A total of 213 double haploid lines were developed the cross between HR26234-12-1-1 conferring resistant to bacterial blight and rice stripe virus and SR30071-3-7-23-6-2-1-1 conferring resistant to brown planthopper, bacterial bight, and rice stripe virus. Using DNA molecular marker, HR26234 and SR30071 were confirmed to have Xa3+xa5+Stvb-i and Bph18+Xa4+Stvb-i, respectively. All double haploid lines carried Stvb-i, and Bph18+Xa3, Bph18+Xa4, Bph18+Xa3+xa5, Bph18+Xa4+xa5, bph18+Xa3, bph18+Xa4, bph18+Xa3+xa5, and bph18+Xa4+xa5 combinations were identified. Segregation distortions such as no combinations carrying Bph18(or bph18)+xa5+Stvb-i and fewer lines carrying Bph18 than bph18 were occurred in DH population. Brown planthopper resistant lines carrying Bph18 showed longer culm length than susceptible lines. Selected Bph18+Xa4+xa5+Stvb-i combination lines with short culm conferred resistant to brown planthopper, bacterial blight, and rice stripe virus, while showed deleterious effects such as spikelet sterility, lower yield, and vulnerable to lodging than standard and comparative varieties. Using anther culture, we rapidly developed multi-resistant lines to brown planthopper, bacterial blight, and rice stripe virus. However, distorted segregation in DH population and linkage drag with Bph18 were obstacles to develop practical multi-resistant cultivars.