High-Vigor Seeds Associated with Seed Hardness and Water Absorption Rate in Rice ( Oryza sativa L.)

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.