Whitebacked planthopper (WBPH) is a pest that causes serious damage to rice in Asian countries with a mild climate. WBPH causes severely rice yield losses and grain poor quality each year so needs biological control. Plants resist biotic and abiotic stress using expressing variety genes, such as kinase, phytohormones, transcription factors, and especially secondary metabolites. In this research, quantitative trait locus (QTL) mapping was performed by assigning the WBPH resistance score in the Cheongcheong/Nagdong doubled haploid (CNDH) line in 2018 and 2019. The RM280-RM6909 on chromosome 4 was detected as a duplicate in 2018, 2019, and derived from Cheongcheong. This region includes cell function, kinase, signaling, transcription factors, and secondary metabolites that protect plants from the stress of WBPH. The RM280-RM6909 on chromosome 4 contains candidate genes that are similar to the flavanone 3-hydroxylase (F3H) of rice. The F3H are homologous genes, which play an important role in biosynthesis defending against biotic stress in plants. After WBPH inoculation, the relative expression level of F3H was higher in resistant line than in a susceptible line. The newly identified WBPH resistance gene F3H by QTL mapping can be used for the breeding of rice cultivars that are resistant against WBPH.

The brown planthopper (BPH) is a major pest that causes serious damage to rice in countries with mild climates, including Korea, Japan, China, and Vietnam. Although a large number of BPH-resistant genes have been reported, BPH has recently evolved rapidly and in a variable manner due to rapid climate change and an unpredictable environment. The synthesis of secondary metabolites in plants is essential, as it provides resistance to various stressors, including pests such as BPH. For QTL mapping, a Samgang/Nagdong double haploid (SNDH) 113 population was used. The BPH resistance gene was screening by measure the resistance score using the phenotype that appeared after BPH inoculation in the 113 SNDH population. QTL mapping was used, and SSR marker RM584-RM225 of chromosome 6 and SSR marker RM331-S8024 of chromosome 8 were commonly identified. These locations contained transcription factors, phytohormones, signaling molecules, kinases, and secondary metabolites that defend plants from stressors in the environment. This region of chromosome 8 also contained a sequence similar to that of rice Choristmate mutase (OsCM9). CM is a gene that is not only found in rice, but also in thale cress (Arabidopsis thaliana (L.) Heynh.), maize (Zea mays L.), and soybean (Glycine max (L.) Merr.). After inoculation with BPH, the relative expression levels of OsCM9 were greater in the line resistant to BPH than in the line susceptible to BPH. The newly identified BPH-resistant gene OsCM9 can be used for the development of rice varieties that are capable of resisting sudden damage due to BPH, as the evolution of BPH due to climate change has had negative impacts on rice crops.