Background: Improvement in photosynthesis is one of the most promising approaches to increase grain yields. Transgenic rice plants overproducing Rubisco by 30% (RBCS-sense rice plants) showed up to 28% increase in grain yields under sufficient nitrogen (N) fertilization using an isolated experimental paddy field (Yoon et al. in Nat Food 1:134–139, 2020). The plant N contents above-ground sections and Rubisco contents of the flag leaves were higher in the RBCS-sense plants than in the wild-type rice plants during the ripening period, which may be reasons for the increased yields. However, some imprecise points were left in the previous research, such as contributions of photosynthesis of leaves below the flag leaves to the yield, and maintenance duration of high photosynthesis of RBCS-sense rice plants during ripening periods. Result: In this research, the photosynthetic capacity and canopy architecture were analyzed to explore factors for the increased yields of RBCS-sense rice plants. It was found that N had already been preferentially distributed into the flag leaves at the early ripening stage, contributing to maintaining higher Rubisco content levels in the enlarged flag leaves and extending the lifespan of the flag leaves of RBCS-sense rice plants throughout ripening periods under sufficient N fertilization. The higher amounts of Rubisco also improved the photosynthetic activity in the flag leaves throughout the ripening period. Although the enlarged flag leaves of the RBCS-sense rice plants occupied large spatial areas of the uppermost layer in the canopy, no significant prevention of light penetration to leaves below the flag leaves was observed. Additionally, since the CO₂ assimilation rates of lower leaves between wild-type and RBCS-sense rice plants were the same at the early ripening stage, the lower leaves did not contribute to an increase in yields of the RBCS-sense rice plants. Conclusion: We concluded that improvements in the photosynthetic capacity by higher leaf N and Rubisco contents, enlarged leaf area and extended lifespan of flag leaves led to an increase in grain yields of RBCS-sense rice plants grown under sufficient N fertilization.

The availability of inorganic phosphate (P_i) for ATP synthesis is thought to limit photosynthesis at elevated [CO₂] when P_i regeneration via sucrose or starch synthesis is limited. We report here another mechanism for the occurrence of P_i-limited photosynthesis caused by insufficient capacity of chloroplast triose phosphate isomerase (cpTPI). In cpTPI-antisense transgenic rice (Oryza sativa) plants with 55%–86% reductions in cpTPI content, CO₂ sensitivity of the rate of CO₂ assimilation (A) decreased and even reversed at elevated [CO₂]. The pool sizes of the Calvin–Benson cycle metabolites from pentose phosphates to 3-phosphoglycerate increased at elevated [CO₂], whereas those of ATP decreased. These phenomena are similar to the typical symptoms of P_i-limited photosynthesis, suggesting sufficient capacity of cpTPI is necessary to prevent the occurrence of P_i-limited photosynthesis and that cpTPI content moderately affects photosynthetic capacity at elevated [CO₂]. As there tended to be slight variations in the amounts of total leaf-N depending on the genotypes, relationships between A and the amounts of cpTPI were examined after these parameters were expressed per unit amount of total leaf-N (A/N and cpTPI/N, respectively). A/N at elevated [CO₂] decreased linearly as cpTPI/N decreased before A/N sharply decreased, owing to further decreases in cpTPI/N. Within this linear range, decreases in cpTPI/N by 80% led to decreases up to 27% in A/N at elevated [CO₂]. Thus, cpTPI function is crucial for photosynthesis at elevated [CO₂].

The Green Revolution allowed a large amount of nitrogen (N) fertilization to increase crop yield but has led to severe environmental pollution. Therefore, increasing the crop grain yield must be achieved without such considerable input of N fertilization. A large‐grain japonica rice cultivar, Akita 63, significantly increased grain yield and improved N‐use efficiency (NUE) for yield per amount of N absorbed by plants. This study found that the nonsense mutated GS3 gene, the gs3 allele of Akita 63, has a superior yield production with enlarged grain size. The gs3 allele increased the yield with improvements in harvest index and NUE for yields per plant N content by analyzing the near‐isogenic line of rice plants with a large grain (LG‐Notohikari), which was developed by introducing the gs3 allele of Akita 63 into normal‐grain japonica cultivar, Notohikari. Thus, the gs3 allele would be promising for further yield increase without additional large input of N fertilization in non‐gs3‐allele rice varieties.

Bakanae disease (BD), caused by the fungal pathogen Fusarium fujikuroi, is a serious threat to rice production worldwide. Breeding elite rice varieties resistant to BD requires the identification of resistance genes. Previously, we discovered a resistant quantitative trait locus (QTL), qFfR1, in a Korean japonica rice variety, Nampyeong. In this study, we fine-mapped qFfR1 with a Junam^*4/Nampyeong BC₃F₃ population and delimited its location to a 37.1 kb region on chromosome 1. Complementation experiments with seven candidate genes in this region revealed that OsI_02728 is the gene for qFfR1. This gene encodes a protein with a typical leucine-rich repeat (LRR) receptor-like protein structure. RNA-sequencing-based transcriptomic analysis revealed that FfR1 induces the transcription of defense genes, including lignin and terpenoid biosynthesis genes, pathogenesis-related genes, and thionin genes. These results may facilitate investigations into the molecular mechanisms underlying BD resistance, including molecular patterns of Fusarium fujikuroi interacting with FfR1 and players working in signal transduction pathways downstream of FfR1, and the breeding of new BD-resistant varieties by providing a BD resistance gene with its precise selection marker. This will contribute to efficient control of BD, which is becoming more prevalent according to temperature rises due to climate change.

A double-cropping system is widely adopted in southern Korea, in which the sowing date of the second crop (soybean) can be delayed depending on the growth period of the first crop and weather conditions. Soybean yields may be reduced because of the shorter vegetative growth period and earlier flowering. This study examined soybean growth and yield responses as plant populations at a late planting date. A field experiment was conducted in the upland field at the Department of Southern Area Crop Science in Miryang, Gyeongsangnam-do, for two years (2022–2023) using four cultivars (Seonyu 2, Jungmo 3015, Seonpung, and Jangpung). A split-plot block design was used with three replications. The main plots had four sowing dates at 10-day intervals from 25 June to 25 July. The date of maturity was recorded, and the yield components and yield were examined after harvesting. The optimum planting population for maximizing the soybean yield with late planting was compared with the standard population result. To maintain pre- and post-crop yields and cultivate stable production, the sowing date limit for early maturing soybeans was July 15 and that for mid-maturing soybeans was July 5. The results highlight the potential to produce an economic soybean production level.

Wild teas are valuable genetic resources for studying evolution and breeding. Here, we report the complete chloroplast genome of the ancient Korean tea ‘Hadong Cheon-nyeon Cha’ (C. sinensis var. sinensis), which is known as the oldest tea tree in Korea. This study determined seven Camellia sinensis var. sinenesis, including Hadong Cheon-nyeon Cha (HCNC) chloroplast genome sequences, using Illumina sequencing technology via de novo assembly. The chloroplast genome sizes ranged from 157,019 to 157,114 bp and were organized into quadripartite regions with the typical chloroplast genomes. Further, differences in SNPs and InDels were detected across the seven chloroplast genomes through variance analysis. Principal component and phylogenetic analysis suggested that regional constraints, rather than functional constraints, strongly affected the sequence evolution of the cp genomes in this study. These genomic resources provide evolutionary insight into Korean tea plant cultivars and lay the foundation for a better understanding of the ancient Korean tea plant HCNC.