The isolation and characterization of genes that control tillering in rice

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In rice cultivation, the genetic control of the tillering has been important. The present research project was conducted to elucidate what genes are involved in the natural variant in tillering in cultivated rice. In maize, the tb1 (toesinte branched 1) has been known as a gene that control the tillering including its natural variants. I targeted the rice ortholog of this gene for this research project. Using Asominori rice x IR24 rice recombinant inbred lines as a mappin population the comparative mapping of the maize tb1 probe was performed. The tb1 probe was mapped near the marker C1351 in the rice chromosome 3. Since this region of rice chromosomes is syntenic with the long arm of the maize chromosome 1 where the tb1 is located, the mapped gene is considered to be the rice ortholog of the maize tb1 gene. A co-segregation analysis revealed that this rice tb1 gene is tightly linked to the phenotype of a mutant that tillers profusely. This fact, in combination with the fact that the loss-of-function mutant of tb1 tillers profusely, suggests that the rice tb1 controls tillering like maize tb1. Since one of the reported QTLs for tiller number is located near the locus of the rice tb1, it is highly probable that this gene is a cause of natural variant of tillering.