Internode length and stem diameter are the primary traits affecting the lodging resistance of rice. Traits related to the length of the panicle (LP), uppermost internode (LUI), second internode (LSI), third internode (LTI), fourth internode (LFI), lowest internode (LLI) as well as stem diameter at the uppermost internode (SDUI), second internode (SDSI), third internode (SDTI), fourth internode (SDFI), and lowest internode (SDLI) in 120 Cheongcheong/Nagdong doubled haploid population were investigated using a quantitative trait locus (QTL) analysis. Thirty-four QTL regions affected LP and the length of each internode. Twenty-six QTL regions were associated with the stem diameter of each internode. RM12285-RM212 on chromosome 1 contained 10 QTLs related to the internode length, which have overlapped for over 2 years. Twenty-three candidate genes were screened using mark interval. Among the candidate genes, Os01g0803900, named OsCYPq1, which is in the Cytochrome P450 family, might be involved in gibberellins (GA) synthesis. GA is an essential plant growth regulator that affects plant height. OsCYPq1 catalyzes oxidation steps in the middle part of the GA pathway. OsCYPq1 is expected to provide valuable information to improve the marker assessment for target traits and QTL gene cloning in rice.

Rice (Oryza sativa L.) is one of the essential staple foods for more than half of the world’s population, and its production is affected by different environmental abiotic and biotic stress conditions. The white-backed planthopper (WBPH, Sogatella furcifera) causes significant damage to rice plants, leading to substantial economic losses due to reduced production. In this experiment, we applied exogenous hormones (gibberellic acid and methyl jasmonate) to WBPH-infested rice plants and examined the relative expression of related genes, antioxidant accumulation, the recovery rate of affected plants, endogenous hormones, the accumulation of H₂O₂, and the rate of cell death using DAB and trypan staining, respectively. The expression of the transcriptional regulator (OsGAI) and gibberellic-acid-mediated signaling regulator (OsGID2) was upregulated significantly in GA 50 µM + WBPH after 36 h. OsGAI was upregulated in the control, GA 50 µM + WBPH, GA 100 µM + WBPH, and MeJA 100 µM + WBPH. However, after 48 h, the OsGID2 was significantly highly expressed in all groups of plants. The glutathione (GSH) values were significantly enhanced by GA 100 µM and MeJA 50 µM treatment. Unlike glutathione (GSH), the catalase (CAT) and peroxidase (POD) values were significantly reduced in control + WBPH plants. However, a slight increase in CAT and POD values was observed in GA 50 + WBPH plants and a reduction in the POD value was observed in GA 100 µM + WBPH and MeJA 50 µM + WBPH plants. GA highly recovered the WBPH-affected rice plants, while no recovery was seen in MeJA-treated plants. MeJA was highly accumulated in control + WBPH, MeJA 50 µM + WBPH, and GA 100 µM + WBPH plants. The H₂O₂ accumulation was highly decreased in GA-treated plants, while extensive cell death was observed in MeJA-treated plants compared with GA-treated plants. From this study, we can conclude that the exogenous application of GA can overcome the effects of the WBPH and enhance resistance in rice.

Rice tillers are one of the most important traits for the yield and development of rice, although little is known about its mode of inheritance. Tiller numbers were recorded every 7 days a total of nine times, starting 30 days after transplantation. Quantitative trait locus (QTL) based analysis on a set of double haploid population derivatives of a cross between the Cheongcheong and Nagdong varieties identified a major effect of locus RM18130–RM3381 on chromosome 5, which was expressed in eight different growth stages. Within the target region RM18130–RM3381 (physical distance: 2.08 Mb), 61 candidate genes were screened by annotation. Among the candidate genes, Os05g0230700 (named OsIAA17q5), which belongs to the family of auxin-responsive genes, was selected as a target. Auxin promotes cell division and meristem maintenance and is an effective plant regulator which influences plant growth and development by altering the expression of various genes. OsIAA17q5 is expected to control the number of tillers. The present study provides further understanding of the basic genetic mechanisms that selectively express the control of tiller numbers in different growth stages, as well as provides valuable information for future research aimed at cloning the target gene. These results may contribute to developing a comprehensive understanding of the basic genetic processes regulating the developmental behavior of tiller numbers in rice.

Brown planthopper (BPH, Nilaparvata lugens Stal.) is the most damaging rice pest affecting stable rice yields worldwide. Currently, methods for controlling BPH include breeding a BPH-resistant cultivar and using synthetic pesticides. Nevertheless, the continuous cultivation of resistant cultivars allows for the emergence of various resistant races, and the use of synthetic pesticides can induce environmental pollution as well as the emergence of unpredictable new pest species. As plants cannot migrate to other locations on their own to combat various stresses, the production of secondary metabolites allows plants to protect themselves from stress and tolerate their reproduction. Pesticides using natural products are currently being developed to prevent environmental pollution and ecosystem disturbance caused by synthetic pesticides. In this study, after BPH infection in rice, chrysoeriol7 (C7), a secondary metabolite that induces resistance against BPH, was assessed. After C7 treatment and BPH infection, relative expression levels of the flavonoid-related genes were elevated, suggesting that in plants subjected to BPH, compounds related to flavonoids, among the secondary metabolites, play an important role in inducing resistance. The plant-derived natural compound chrysoeriol7 can potentially thus be used to develop environmentally friendly pesticides. The suggested control of BPH can be effectively used to alleviate concerns regarding environmental pollution and to construct a relatively safe rice breeding environment.

We detected a new target quantitative trait locus (QTL) for lodging resistance in rice by analyzing lodging resistance to typhoons (Maysak and Haishen) using a scale from 0 (no prostrating) to 1 (little prostrating or prostrating) to record the resistance score in a Cheongcheong/Nagdong double haploid rice population. Five quantitative trait loci for lodging resistance to typhoons were detected. Among them, qTyM6 and qTyH6 exhibited crucial effects of locus RM3343–RM20318 on chromosome 6, which overlaps with our previous rice lodging studies for the loci qPSLSA6-2, qPSLSB6-5, and qLTI6-2. Within the target locus RM3343–RM20318, 12 related genes belonging to the cytochrome P450 protein family were screened through annotation. Os06g0599200 (OsTyM/Hq6) was selected for further analysis. We observed that the culm and panicle lengths were positively correlated with lodging resistance to typhoons. However, the yield was negatively correlated with lodging resistance to typhoons. The findings of this study improve an understanding of rice breeding, particularly the culm length, early maturing, and heavy panicle varieties, and the mechanisms by which the plant’s architecture can resist natural disasters such as typhoons to ensure food safety. These results also provide the insight that lodging resistance in rice may be associated with major traits such as panicle length, culm length, tiller number, and heading date, and thereby improvements in these traits can increase lodging resistance to typhoons. Moreover, rice breeding should focus on maintaining suitable varieties that can withstand the adverse effects of climate change in the future and provide better food security.