Introduction of the Long-Coleoptile Trait to Improve the Establishment of Direct-Seeded Rice in Submerged Fields in Cool Climates

摘要

Introduction of the long-coleoptile trait in European varieties into Japanese elite varieties may improve seedling establishment and yield stability of the rice in the direct-seeding cultivation in cool climates. Some European varieties have long coleoptiles but they also have undesirable traits such as low yielding ability and bad grain appearance, which makes it difficult to improve coleoptile length in a rice breeding programs in Japan. To overcome this difficulty, we introduced the long-coleoptile trait of Arroz da Terra (Portuguese variety with long coleoptile) into Kitaibuki Uapanese elite variety for direct seeding cultivation) by backcrossing. Furthermore, we confirmed the effectiveness of introducing the long-coleoptile trait for the selection of lines with stable seedling establishment. The coleoptile length of Satsukei00019, a near isogenic line of Kitaibuki for the long-coleoptile trait, was about twice as long as that of Kitaibuki. The seedling establishment rate of Satsukei00019 was about 20% higher than that of Kitaibuki in the direct seeding cultivation in submerged fields. Eating quality, heading date and yield of Satsukei00019 were similar to those of Kitaibuki but 1, 000 grain weight of Satsukei00019 was larger. Therefore, the efficacy of backcross breeding to introduce the long-coleoptile trait of European varieties into Japanese elite varieties was confirmed. From these results, we concluded that the selection based on a longer coleoptile length improved seedling establishment in submerged fields in cool climates which can contribute to stable production of direct seeded rice.