Mapping of quantitative trait loci for gibberellic acid response at rice (Oryza sativa L.) seedling stage

The development of molecular genetic maps has accelerated the identification and mapping of genomic regions controlling quantitative trait loci (QTLs) in rice. The degree of gibberellin response affects various physiological processes in plant growth and development. This study was conducted to map QTLs for gibberellic acid (GA(3)) response in the rice seedling stage in a recombinant inbred (RI) population derived from a cross of a japonica variety, Asominori (lower GA(3) response), with an indica variety, IR24 (higher GA(3) response), using 289 RFLP markers. Continuous phenotypic variation of GA(3) response index and transgressive segregation in both parental directions were observed, suggesting that GA(3) response in regard to seedling plant height was a quantitatively inherited trait in the RI population. Five QTLs controlling GA(3) response were identified and mapped to chromosomes 1, 3, 4, 6 and 12, respectively. Among them, the largest effect QTL (qGAR-1), located between G2200 and C86 on chromosome 1, explained 28.2-34.1% of the total phenotypic variation. The second largest effect QTL (qGAR-12) was detected near C751 on chromosome 12 and accounted for 13.2-16.5% of total variation. The remaining three QTLs on chromosome 3, 4 and 6, explained 5.1-6.4% of total phenotypic variation, respectively. In addition, alleles with increasing and decreasing GA(3) response effects were detected from both parents. The molecular markers tightly linked to GA(3) response QTLs lead to the isolation of loci and will help us to better understand GA(3) response mechanisms in rice. (c) 2005 Elsevier Ireland Ltd. All rights reserved.