Isolation of a QTL gene controlling grain number and QTL pyramiding to combine loci for grain number and plant height in rice
2007
Ashikari, M. | Lin, S. | Yamamoto, T. | Takashi, T. | Nishimura, A. | Angeles, E.R. | Qian, Q. | Kitano, H. | Matsuoka, M.
Many agronomically important traits, including yield, are expressed in continuous phenotypic variation. These complex traits usually are governed by a number of genes known as quantitative trait loci (QTLs) derived from natural variations. Now, QTL analysis has been employed as a powerful approach to discover agronomically useful genes. Grain number and plant height are important are important traits that directly contribute to grain productivity. We aimed to identify genes of QTLs for grain number and plant height, not only to elucidate molecular mechanisms that regulate grain productivity but also to use these genes for breeding. We first identified that a QTL that increases grain productivity in rice, Gn1a, is a gene for cytokinin oxidase/dehydrogenase (OsCKX2), an enzyme that degrades the phytohormone cytokinin. Reduced expression of OSCKX2 causes cytokinin accumulation in inflorescence meristems and increases the number of reproductive organs, resulting in enhanced grain yield. QTL pyramiding to combine loci for grain number and plant height in the same genetic background generated lines exhibiting both beneficial traits. These results provide a strategy for tailor-made crop improvement. Discovering useful genes, improving agricultural traits hidden in the plant genome, and applying these findings to crop breeding will pave the way for a new green revolution.
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