Combining Ability in the Rice Lines Selected for Direct-Seeding in Flooded Paddy Field

Summary

To estimate the general and specific combining ability for direct seeding in flooded paddy field, we completed a 4 × 3 factorial crossing (design II) in 1998, and evaluated the 12 F¹ hybrids and their 7 parents, including selected lines for yield, yield components and culm traits in 1999. Generally, parents with good combining ability produce good lines in later generations. Therefore, the basic information about the general combining ability (GGA) and specific combining ability (SGA) is valuable for breeding cultivars. The effect of GGA was significant for culm length, culm thickness, panicle length, 1000-grain weight and grain yield, which indicated the importance of the additive effects of the genes for these traits. The effects of dominant genes were significant for culm length, culm thickness and grain yield, indicating that these traits were also controlled by nonadditive gene actions. Mid-parent heterosis ranged from -16.3% to 37% with an average value of 17.3% for grain yield, and from -1.7% to 30.0% with an average value of 13% for culm length, and from -6.1% to 23.9% with an average value of 4.2% for culm thickness. Some parents with positive GCA for yield, culm thickness and panicle length were identified. They would be useful for developing cultivars adapted to direct-seeding in flooded paddy fields.