MYB-type transcription factors play essential regulatory roles in seed germination and the response to seedling establishment stress. This study isolated a rice R2R3-MYB gene, OsMYBAS1, and functionally characterized its role in seed germination by generating transgenic rice plants with the overexpression and knockout of OsMYBAS1. Gene expression analysis suggested that OsMYBAS1 was highly expressed in brown rice and root, respectively. Subcellular localization analysis determined that OsMYBAS1 was localized in the nucleus. No significant differences in seed germination rate were observed among wild-type (WT) and transgenic rice plants at the 0-cm sowing depth. However, when sown at a depth of 4 cm, higher germination rates, root lengths and seedling heights were obtained in OsMYBAS1-overexpressing plants than in WT. Furthermore, the opposite results were recorded between the osmybas1 mutants and WT. Moreover, OsMYBAS1-overexpressing plants significantly enhanced superoxide dismutase (SOD) enzyme activity and suppressed the accumulation of malondialdehyde (MDA) content at the 4-cm sowing depth. These results indicate that the MYB transcription factor OsMYBAS1 may promote rice seed germination and subsequent seedling establishment under deep-sowing conditions. These findings can provide valuable insight into rice seed-quality breeding to facilitate the development of a dry, direct-seeding production system.

Gibberellic acid (GA₃) application after anthesis is an important practice in hybrid rice seed production, and it plays diverse roles in seed quality and seed yield. The main objective of this study was to determine (1) the effects of GA₃ application after anthesis on seed vigor and (2) the optimal GA₃ dosage applied to Indica hybrid rice seed production. Field experiments of different GA₃ dosages (15 g hm⁻² and 30 g hm⁻², respectively) after anthesis were conducted in 2016 and 2017, and seed vigor parameters, stigma vigor index, and seed yield were determined. We found that significant differences in seed vigor parameters by a standard germination test and a cool germination test were observed among different GA₃ dosages after anthesis. Compared with the water spraying treatment, the germination percentage (GP) increased by 2.5–6.3%, and the vigor index (VI) increased by 8.9–19.8% from GA₃ application after anthesis, respectively. Moreover, the stigma vigor index of the female parent was enhanced with an increasing GA₃ dosage, and there were significant increases (7.5–16.0%) between the water spraying treatment and GA₃ spraying treatments. There were positive significant relationships between the VI and stigma vigor index. Additionally, the seed yield of the GA₃ application with 30 g hm⁻² was 3.9% higher on average than that of the water spraying treatment. Therefore, our study suggests that seed vigor can be increased by GA₃ application after anthesis, and GA₃ application should be applied at a rate of 30 g hm⁻² to improve seed vigor and maintain seed yield in Indica hybrid rice seed production.

Seed physical properties are stable and visualized, and believed to be reference indicators for screening high-vigor seeds. However, the detailed relationship between seed vigor and its physical properties is not fully understood in rice. To elucidate the relationship mentioned above, seed physical properties such as seed size, hardness, and water absorption rate, and seed vigor indicators including germination rate, salt-stressed germination rate, and drought-stressed germination rate were determined among different rice cultivars. Significant differences in seed vigor indicators and seed physical properties were recorded among different rice cultivars. Germination rate, salt-stressed germination rate, drought-stressed germination rate, seed hardness, and water absorption rate ranged from 32.0 ± 1.7% to 99.7 ± 0.3%, 14.4 ± 2.4% to 99.7 ± 0.3%, 3.3 ± 2.6% to 95.7 ± 2.1%, 69.15 ± 0.15 N to 74.56 ± 0.14 N, and 0.09 ± 0.00 g/h to 0.12 ± 0.00 g/h, respectively. Additionally, correlation analysis showed that seed hardness and water absorption rate were significantly positively related to seed vigor (r = 0.33 **−0.41 **, from 2014 to 2016; r = 0.45 **−0.65 **, in 2021). Moreover, principal component analysis determined that the first principal component explained 91.4%, 90.1%, and 89.9% of the variance of seed physical properties, respectively, and loaded on seed hardness and water absorption rate. These results indicate that seed hardness and water absorption rate can be recommended as efficient indicators for screening rice seeds with high vigor.

MYB-type transcription factors play an essential regulatory role in seed germination and the response to seedling establishment stress. This study isolated a rice R2R3-MYB transcription factor, OsMYBAS1, and functionally characterized its role in seed germination. There was no significant difference in the germination rate of each transgenic line in the standard germination test. However, compared to the germination rate of the wild type (WT) measured in the artificial accelerated aging test, the germination rates of the overexpression lines OE-OsMYBAS1-1 and OE-OsMYBAS1-2 were significantly increased by 25.0% and 21.7%, respectively. In contrast, the germination rates of the knockout mutants osmybas1-1 and osmybas1-2 were decreased by 21.7% and 33.3%, respectively. Additionally, the above data indicated that OsMYBAS1 possibly plays a positive role in rice seed germination. Moreover, the antioxidant enzyme activities of OsMYBAS1-overexpressing plants were enhanced by 38.5% to 151.0% while the superoxide dismutase (SOD) enzyme activity of osmybas1 mutants was decreased by 27.5%, and the malondialdehyde (MDA) content was increased by 24.7% on average. Interestingly, the expression of the antioxidation-related genes OsALDH3, OsAPX3, and OsCATC was enhanced in the OsMYBAS1 overexpression lines, which is consistent with the above results. Furthermore, transcriptome sequencing determined 284 differentially expressed genes (DEGs), which were mainly involved in the carbohydrate metabolic process, glycerolipid metabolism, and glycerophospholipid metabolism. Therefore, these findings provide valuable insight into the breeding of new rice varieties with high seed germination.

This study introduces a versatile seed 3D reconstruction method that is applicable to multiple crops—including maize, wheat, and rice—and designed to overcome the inefficiency and subjectivity of manual measurements and the high costs of laser-based phenotyping. A panoramic video of the seed is captured and processed through frame sampling to extract multi-view images. Structure-from-Motion (SFM) is employed for sparse reconstruction and camera pose estimation, while 3D Gaussian Splatting (3DGS) is utilized for high-fidelity dense reconstruction, generating detailed point cloud models. The subsequent point cloud preprocessing, filtering, and segmentation enable the extraction of key phenotypic parameters, including length, width, height, surface area, and volume. The experimental evaluations demonstrated a high measurement accuracy, with coefficients of determination (R²) for length, width, and height reaching 0.9361, 0.8889, and 0.946, respectively. Moreover, the reconstructed models exhibit superior image quality, with peak signal-to-noise ratio (PSNR) values consistently ranging from 35 to 37 dB, underscoring the robustness of 3DGS in preserving fine structural details. Compared to conventional multi-view stereo (MVS) techniques, the proposed method can achieve significantly improved reconstruction accuracy and visual fidelity. The key outcomes of this study confirm that the 3DGS-based pipeline provides a highly accurate, efficient, and scalable solution for digital phenotyping, establishing a robust foundation for its application across diverse crop species.

Application of plant growth regulators emerges as one of the most reliable methods to enhance crop productivity and quality. However, knowledge is limited in seed quality of hybrid rice subjected to exogenous 6-Benzyladenine (6-BA) application during seed development. A 2-year experiment was conducted to investigate the effects of 6-BA treatment after pollination on seed vigor and its underlying regulatory mechanisms. Results showed that 6-BA treatment increased germination potential (GP) and vigor index (VI) of hybrid rice irrespective of cultivar and year, particularly with 50 mg/L. Consistently, seedling quality including seedling height, root length and dry weight was significantly enhanced under 6-BA treatment with 50 mg/L. Based on the results above, 50 mg/L was considered as the optimal concentration. Additionally, 6-BA treatment with 50 mg/L increased catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) activities, and it strongly induced the expression of OsAPX1 and OsCSD3 related to antioxidant enzyme activity at the early stage of seed emergence. Therefore, spraying 6-BA with 50 mg/L after pollination could be recommended as an agronomic practice for hybrid rice seed production with high seed vigor.