Relationship between seed traits and seedling parameters in rice wild species

Rice is the staple food and source of carbohydrates for about half of the world’s population. The demand for rice is continuously increasing because of the ever growing human population. Climate change and ever decreasing under-ground water resources necessitates diversifying cultivation of rice through the direct seed sowing. Seeds with high seedling vigour and good crop stands are preferred under direct seeding condition. Therefore, the present study was undertaken to analyse seed traits and their effects on seedling vigour and grain yield in wild and cultivated species of rice. Seeds from 28 accessions of wild and cultivated species were used and grouped into three sizes (short, medium, and long) and two shapes (medium and slender). A significant effect of seed size was observed on embryo length, embryo area, the ratio of embryo area to seed area and all seedling traits as well as grain yield. Seed shape had a significant effect on embryo length and seedling traits including grain yield, but it was non-significant on root length and germination percentage. A significant positive correlation was observed between the embryo area, grain yield, germination percentage, nodal root number, and seedling height. Large seeds had larger embryos and better seedling vigour. The cultivated Oryza sativa genotypes had the largest embryo and seed areas, followed by O. meridionalis. O. glaberrima had the smallest embryo area. The seed size was observed to evolve under selection pressure and the larger seed sizes in O. sativa cultivars indicated gradual selection for increased seed size and fitness under agronomic conditions.